爱华网Light Fixtures—The Basic
HMI Arsenal
HMI Fixtures
HMI lights1 are a highly efficient source of daylight-balancedlight (5600 or
6000 K, depending on the globe manufacturer). Havingdaylight-balanced lights is
essential in a number of scenarios:
1. When artificial light needs to mix with natural daylight, aswhen shooting day
exterior scenes or inside a building with lots of windows.
2. When shooting tungsten-balanced scenes that require blue“moonlight” (e.g.,
Terminator II, or any other James Cameron movie for thatmatter).
3. When shooting a tungsten-balanced scene, if you have no otherbig
lights. In this case, a full correction (CTO) gel would be used infront of
the light.
An HMI puts out about four times as much light as a tungsten lightof the
same wattage, 85–108 lumens per watt of electricity, compared to 26lumens per
watt for tungsten halogen bulbs. This is partly because anincandescent bulb expends
80% of its energy creating heat (infrared wavelengths), whereasHMIs convert that
same percentage of its energy into usable illumination. As aresult, HMIs operate
somewhat cooler than their tungsten equivalents.
An HMI light uses a ballast connected between the AC power sourceand the
lamp head. The component parts of an HMI are the head, the headcable, the ballast,
and in most cases a separate ballast cable (Figure 4.1). StandardHMIs run on AC
power only (Lightmaker AC/DC models have gone intoretirement).
1HMI is the registered trade name of Osram for its discharge lamps;however, HMI has become
the common name referring to all lamps of its class, regardless ofmanufacturer. The many other
manufacturers and trade names are covered later in thischapter.
70 SET LIGHTING TECHNICIAN’S HANDBOOK
There are two types of ballasts: magnetic, the original type ofpower supply,
and electronic (also called square wave or flicker free), which arebecoming more
and more common. More about this shortly.
There are several types of HMI fixtures: Fresnels, PARs, open face,soft lights,
and battery-powered sun guns. Specifications for HMI fixturesappear in Appendix A.
HMI Fresnels
Small Fresnels of 200, 575, and 1200 W are commonly used asinterior direct
light or bounce light when daylight color balance is needed. Theyare equivalent in
function to a tweenie, a baby, and a junior, respectively. Thesesizes have the
advantage of plugging into a standard household outlet whennecessary. Medium-size
Figure 4.1 LTM 1200 HMI PAR head, head cable, ballast cable,ballast, scrims, lens
case, and set of spreader lenses.
Light Fixtures—The Basic HMI Arsenal 71
HMI Fresnels of 2500, 4000, and 6000 W are used in much the samemanner as 5k
and 10k tungsten units—to light large interiors, to double assunlight, to provide fill
on exteriors, or to provide key light and backlight on nightexteriors.
Large HMI Fresnels—12k and 18k—have replaced the carbon arc asthe
workhorse large light. A necessary part of almost any equipmentpackage, 12ks are
used for fill on day exterior shots or to cover wide exterior nightshots. One or two
are very often mounted to an aerial lift (Condor) to light up acity block from 80 ft
in the air. Another common application is making sunlight effectsthrough windows,
both on location and inside the studio. They may be put throughdiffusion or bounced
to create a large, bright soft source.
HMI PARs
PAR lights are more efficient than Fresnels, and they deliver astrong punch
of light with a longer throw. They come with a case of three orfour spreader lenses
(Figure 4.2 and Table A.6). They come in sizes 200 W, 400 W, 800 W,575 W,
1200 W, 2.5k, 4k, 6k, and 12k.
The term PAR is actually somewhat outdated for HMIs. When HMIPARs
were first designed, they were built like a PAR-64, with bulb,reflector, and UV
lens all in one sealed unit. Today’s HMI PAR lights use asingle-ended HMI globe.
It is axially mounted in the fixture in front of a highly efficientparabolic reflector.
Figure 4.2 A workhorse of film production: the LTM 2500W Cinepar.(Courtesy of LTM
Corp., Los Angeles, CA.)
72 SET LIGHTING TECHNICIAN’S HANDBOOK
UV-protective glass covers the front of the unit, and the spreaderlens slides into
slots in the ears (see Table A.6).
The spreader lenses affect both the shape and angle of the beam.For example,
for a typical 1200-W PAR, the very narrow and narrow spot lensesgive a circular
beam of 6
° and 8
°, respectively. The medium and wide flood lenses give a wide
elliptical beam of 27
°
× 11
°, and 60
°
× 25
°, respectively. The superwide flood gives
a circular beam of about 54
°. To turn an oblong beam, the operator rotates the lens.
Some PAR fixtures also have spot/flood adjustment. When used withspreader
lenses, the spot/flood functions best as a focusing adjustment, tosmooth out the
field. The adjustment for a smooth field differs depending on thelens in use.
Accessories for HMI Fresnel and PAR Lights
HMI Fresnels and PARs use the standard accessories as theirtungsten counterparts:
barn doors, scrims, gel frames. Chimera lightbanks are often usedto turn
direct light into soft light. When HMIs are used for theatrical(stage) and event
lighting, DMX-controlled shutters enable the light to be controlledfrom the dimmer
board. DMX-controlled shutters and color scrollers are valuableaccessories when
this kind of control is required. (DMX-controlled ballasts arecovered under Square-
Wave Electronic Ballasts, later in this chapter.)
HMI “Open-Face” Lights
The Arri X series and Desisti Goya lights are open-face lights inthe sense
that they have only clear UV protective glass in front of the bulband reflector, no
lens (Figure 4.3). Specifications are given in Table A.8. Whiletheir beam is broad
Figure 4.3 Arri X Light. (Courtesy of Arri Lighting, NewYork.)
Light Fixtures—The Basic HMI Arsenal 73
and unfocused, these fixtures have the unique ability to beoriented in any direction.
They can be used pointing straight down as an overhead soft light(through heavy
diffusion) or straight up for architectural lighting. They cast ahard shadow and
would be a good choice if a hard silhouette were needed. They comesizes 200 W,
575 W, 1200 W, 2.5k, 4k, and 6k.
HMI Soft Lights
As with incandescent soft lights, the lamp of an HMI soft light isaimed into
a white concave reflector. The bounced light and large aperturecreate a soft, even
field of daylight-balanced light. The HMI soft light, of course,produces much greater
quantities of light than an incandescent (see Table A.8). Althoughthey are more
popular in Europe, you see few HMI soft lights on set; they areexpensive and
softening accessories like chimeras make them somewhatredundant.
The Aurasoft light is a large round soft-light fixture that can befitted with
either an HMI lamp or tungsten lamp. It is popular among some DPsmainly because
the round shape makes a pleasing eye light.
Small HMI Fixtures—Sun Guns and Modular
Multiuse Fixtures
Sun Guns
A sun gun is a small (125, 200, 250, or 400 W) light powered by a30-V
nickel-cadmium (nicad) battery, usually in the form of a batterybelt (Figure 4.4,
Table A.7).
Figure 4.4 This HMI sun gun takes a 250-W SE HMI globe and has acolor temperature
of 5600 K. It operates on a 30-V battery belt and is adaptable to a24-V car-type battery.
74 SET LIGHTING TECHNICIAN’S HANDBOOK
The light has a handgrip as well as a mounting stud. Sun guns aresometimes
employed in remote locations where power is not available (e.g., acave in the
mountains of Mexico) and in situations where the expediency of abattery-powered
light takes priority (e.g., a moving vehicle or on a movingelevator).
Although the 30-V nicad belt batteries are supposed to last as longas an hour,
rented batteries rarely keep the light going for more than 20–25minutes. Lithium
batteries have greater amp-hour capacity and are preferable. Whenbattery-powered
lights are to be relied on over the course of a whole scene or awhole day, it is
necessary to have many batteries on hand. They must be fullycharged overnight (8
hours), and it helps to have them “topped-off” again within an hourprior to use.
Joker-Bug
A number of manufacturers have adaptations for smalldaylight-balanced
fixtures worthy of special note. K-5600 Lighting manufactures theJoker-Bug lights
(200, 400, and 800 W), which are small fixtures designed with aunique range of
applications: a highly directional PAR light, a soft light orlantern, a linear tube
light, or an ellipsoidal spotlight (Figure 4.5). In the Joker mode,the light is a small
PAR fixture using an axially mounted single-ended MSR bulb in aparabolic, highly
efficient reflector. The lights are very bright for their size. Thespreader lenses allow
wide control (the 400 ranges from a punchy 5
° beam to a generous 55
° spread). In
the Bug mode, the “beamer” (the front housing containing thereflector) is removed,
leaving only a bare omnidirectional bulb held in a UV protectivebeaker. The Bug
is used to illuminate a Chimera light bank or china lantern. Thebulb can be oriented
in any position. For this application, the clear beaker isexchanged for a frosted one,
which helps diffuse the source. Both the 200 and 400 Joker-Bug canrun on battery
packs using the Slimverter power supply, making the 400 one of thebrightest sun
guns available. They can also be run on any type of AC power.
The Softtube is a 45 in. long by 6 in. wide white transluscent tubethat attaches
to the front of the Joker-Bug light. It radiates soft light andinhabits a very small
space, making it ideal for small spaces where daylight fill isneeded (e.g., lighting
a bus interior).
The Bug can be adapted to the Source Four ellipsoidal spot byremoving the
Source Four lamp housing and inserting the “bug-a-beam” adapterwith the Bug
400. The result is a daylight-balanced ellipsoidal spot with fourtimes more brightness
than normal. The short-arc MSR bulb is well suited to the task; theSource
Four’s beam is clean, sharp, and free of color fringing.
Cinespace
LTM has a similar light design, the Cinespace 125 W/200 W andCinespace 575 W.
These lights have a set of lenses that includes a frosted Fresnelas well as an assortment
of spreader lenses. The front reflector housing twists off to adaptthe light to a lantern
or chimera lightbank. Again, you have the option of a frosted orclear globe cover.
Pocket PAR
Arri’s variation on the theme is the 125-W Pocket PAR, which is aminiature
light with its own unique set of accessories. These include a LightPipe (same idea
Light Fixtures—The Basic HMI Arsenal 75
as the Joker Softtube), a set of four pattern projection lenses(like a focal spot),
and a Flex Light system. The Flex Light is like a fiber opticsystem but uses a
liquid optic tube that increases light transmission and does notsuffer from the
green tendency of fiber optic glass (and it cannot break). Thesystem consists of a
flexible liquid optic tube (in 11
/2-m and 3-m lengths) that attaches to the face of
the Pocket PAR via a light collector attachment. On the other end,a front lens
slides into small flashlightlike holder. The Flex Light kit comeswith three lens
Figure 4.5 The Joker 800 in its many forms. (Courtesy of K5600, LosAngeles, CA.)
76 SET LIGHTING TECHNICIAN’S HANDBOOK
choices as well as color correction filters, a mounting adapter(5
/8-in. female) for
the flashlight end. The Pocket PAR has no omnidirectional Bug modebut can be
fitted with an XXS chimera lightbank to be used as an obie, eyelight, or lantern.
It can be powered from any type of AC service or from a 30-Vbattery pack with
a DC power supply.
Dedo 400D
The Dedo 400D is another small daylight fixture with uniquecharacteristics
and accessories. Dedo lights are known for their extraordinarilysophisticated optical
control. They offer superior light output per watt, a totally cleanbeam that has a
wide focusing range (from 5
° at spot to 50
° at full flood). In the flood position, they
project a completely even field distribution. The ballast isdimmable, plus it has a
boost position for additional light output. It has automatic inputvoltage selection
(90 to 255 V AC). The projection attachment for the 400 series Dedolights has the
sharpest, cleanest beam I have seen on any light. The projectionattachment accessories
include framing shutters, iris, and gobo holder.
HMI Operation
Setting Up
The ballast circuit breakers should be off or the ballast unpluggedwhile
connecting or disconnecting head cables. The breakers should remainoff while
plugging in the power (Figure 4.6).
Head cable connectors (Socapex or VEAM) have multiple pins and athreaded
collar that screws onto their receptacle. Use the keyway to orientthe plug into the
socket. VEAM connectors for 575-, 1200-, 2500-, and 4000-W fixturesare identical,
except that the keyway is oriented differently. To tell the cablesapart many manufacturers
and rental houses color code the connectors or cables asfollows:
Green 575
Yellow 1200
Red 2500
Blue 4k
Be sure to tie a tension relief so that the weight of the headcable does not
pull on the connector, especially with larger lights that haveheavy head cables.
Many electronic power supplies provide dual outputs so they can beused with
more than one wattage light (1.2k/2.4k, 2.4k/4k, 4k/6k, 6k/12k,etc.). Note that both
sockets are continually hot when the ballast is powered and on. Usea cover or tape
over the unused socket.
Junction Boxes
The large Socapex connectors used on some head feeders can beconnected
only to a panel-mounted receptacle and not to another head cable. Ajunction box
(J-box) provides the means of connecting one head cable toanother.
Light Fixtures—The Basic HMI Arsenal 77
Striking
Once the head cable is connected to the head and ballast, plug inthe ballast
and switch on the circuit breakers. With 12k and 18k lamps, placethe bulb in the
full spot position before pushing the on switch. This backs thebulb away from the
lens, so that the lens does not crack from thermal shock. Also, inthe (rare) event
that the globe explodes during warm-up, the chance of shatteringthe lens is minimized.
When 12k bulbs do explode, they often go within the first 5 or 10minutes
of ignition or reignition.
Before pushing the on switch, call out “Striking” to warn peoplethat the light
is about to be ignited. HMIs have on/off switches on both the headand the ballast,
and most models can be turned on and off from either place. Whenyou press the
on switch, the ballast briefly sends a high-voltage ignition chargeto the head, and
this makes a sparking sound. On many electronic ballasts, there isa pause before
the ballast sends the ignition charge, which can be as long as 10seconds.
Figure 4.6 Anatomy of an HMI head and ballast.
78 SET LIGHTING TECHNICIAN’S HANDBOOK
The igniter circuit provides an ignition charge of 5,000–17,000 V,depending
on the size of the globe. The ignition charge creates a brief arcbetween the electrodes
in the globe. Once the flow of electrons is initiated, the ballastbrings the voltage
down to the operating level and regulates the current.
Once sparked, the HMI begins to emit light. From a cold state, ittakes 1–3
minutes for the substances in the globe to vaporize. At the sametime, lamp voltage,
lamp current, luminous flux, and color temperature all reach theirnominal values.
Reigniting a globe that is hot from recent use may presentdifficulty. Hot
gasses inside the globe are under great pressure, creating veryhigh resistance. To
overcome this resistance and ionize the gas between the electrodes,a much higher
ignition voltage is necessary. The electronics of most newerballasts take this into
account and have better hot restrike performance; often, however,an older magnetic
ballast cannot produce sufficient voltage and you have to waituntil the lamp has
cooled (2 or 3 minutes) before you can restrike.
Troubleshooting
When an HMI goes down—won’t strike or starts to flicker—you needto
quickly identify the source of the problem and give the gaffer theinformation right
away. If the problem is immediately fixable, you can give thegaffer a time estimate.
If it is more complicated, you need to explain the situation so thegaffer can decide
what to do, usually based on the time available.
If an HMI will not work, first double-check all the obviouspossibilities. Are
the ballast breakers turned on? Are the cables connected properly?Is a bulb installed?
Is the HMI plugged into the proper voltage? (Some are 120 V, othersare 208, 220,
or 240 V.) If the HMI still doesn’t work, isolate the problem: Isit the head cable,
the head, the globe, the ballast, or the power? Isolating theproblem requires a logical,
methodical approach. You can eliminate possibilities by temporarilyborrowing a
ballast and head cable known to work; this will usually get you tothe heart of the
problem quickly. If the problem is hidden, you may have to changeeach component
before you find its cause. In the worst case, more than one faultypart conspires to
confuse things.
Problems with the Head Cable
The cables, specifically the connectors, are the most common sourceof the
problem. If the indicator lights are on at the ballast and off atthe head and you
get absolutely no response from the head when you try to strike it,the problem is
most likely in the cable or the ballast. Swap the head feeder for anew one to see
if it is malfunctioning. (Note: The neon indicator lights in thehead sometimes burn
out. The light is often integral to the switch, and it is anexpensive part for the
rental house to replace, so you cannot always count on them beingin working
order.)
Very often, the pins of the connectors get pulled back into theconnector because
the strain relief is loose, or the wires get twisted inside theconnector because the
keyway that locks the inside of the connector to the outside sleevehas broken off.
Light Fixtures—The Basic HMI Arsenal 79
Check that all the pins on the connector are flush (same for thereceptacles on the
female connectors).
When the head cables are checked out at the rental house—andperiodically
during shooting—check for missing screws on the strain-relief partof the connectors.
If the strain-relief clamp comes loose, the connections inside canget pulled out and
twisted. Dirty connector pins may also be at fault, in which casethe pins should be
blown out with compressed air and cleaned with contact cleaner.Also look for
damaged insulation along the length of the cable. Treat head cableswith care; avoid
dragging them across pavement or throwing them on the groundbecause this can
bend the connectors, making them impossible to connect. Never runhead cables
where heavy equipment and vehicles will run over them; this damagesthe wires
inside, causing endless headaches later on.
For long head feeder runs, it is advisable to go with longer cablesrather than string
together several shorter ones. Using 100-ft cables (available forthe larger units from
Arri) cuts down the number of connection points, which are alwaysthe weakest link.
The pins and keyway are oriented differently for different sizes ofHMIs and
the products of different manufacturers. Check that you are usingthe right head
cable. The keyway orientation normally prevents you from using thewrong kind of
connector, but if the connector is forced into place, it may appearto be connected.
Again, color-coding by wattage of similar-looking head cableshelps.
Problems with the Head
If the indicator light shows that there is power at the head butnothing happens
when you press the button or if the HMI shuts itself off whentilted down, it is likely
that the lens door is slightly loose, allowing the UV protectionmicroswitch to shut
off the unit. Check that the door is tightly closed, even when thelight is tilted
forward. You may need to adjust the rod on the microswitch so thatthe switch
engages. Once in a great while, the microswitch becomes overheated,breaks, and
must be replaced. On newer fixtures, the lamp base tightening knobis also part of
the safety loop circuit. Be sure the lamp base knob is tight or thelamp may not strike.
If the light makes a striking sound but does not take, the problemis most likely
with the globe, igniter circuit, or internal cables. If the globeis hot from prior use,
it is very likely that the globe simply needs a minute to coolbefore it will restrike.
As globes get older, they have more difficulty striking. As theelectrodes wear
away and the gap between them becomes wider, the igniter has togenerate more
voltage to bridge the gap. You may have to try several times beforethe globe takes.
Wait 20 seconds between strikes. It is time to replace the globewhen its electrodes
have worn down so far that the igniter can no longer induce anarc.
With 12k lamps, if the light makes a loud buzz and arcing soundwhen you
attempt to strike but does not take, check the high-voltage (HV)cables and lamp
cables. The lamp cables connect the lamp to terminals at the baseof the lamp holders.
The high-voltage igniter cables run from the base of the lampholders to the igniter
circuit in the base of the head (Figure 4.7).
If the lamp cables hang close to a metal part (such as thereflector), the startup
charge may arc. This deprives the bulb of the necessary startvoltage and, over
80 SET LIGHTING TECHNICIAN’S HANDBOOK
time, burns away the lamp cables. When installing the globe,position lamp cables
so they have plenty of clearance and do not arc to the reflector orlamp housing. If
you find a lamp cable partially burnt (blackened, fraying strandsof cable), do not
use that globe until the lamp cables have been replaced.
Another cause of HV cable burnout is overheating. The cables getjostled
around and the terminal screws loosened, causing overheatedcontacts, which eventually
burn right through the igniter cables or lamp cables. Check andtighten the
terminals each day when the lights are moved around a lot.
Problems with the Ballast
Some magnetic 12k ballasts have a selector switch that must be setat the
appropriate input voltage (208 or 240 V). Improper input voltageselection can
cause trouble in striking and operating the light. The Cinemillsballast has an
internal patch panel instead of a selector switch: To check orchange the input
voltage selection, remove the front panel of the ballast andrepatch the plugs inside.
Some ballasts are self-regulating and require no adjustment to beused with 208-
or 240-V power.
Ballast hum is normal; nonetheless, it is the electrician’s duty toremedy any
annoyance to the sound mixer. It is best, from the start, to placeHMI ballasts in a
separate room. When one ballast is particularly noisy, exchange itfor a new one.
In the meantime, placing sandbags above and below the ballast helpsdampen
vibration. Building a tent with furniture pads also helps, but donot block ventilation.
If a magnetic ballast starts to buzz, it can be a symptom of lowinput voltage.
When operating on a low input voltage, the ballast has to draw morecurrent to
provide the needed voltage to the head. This can cause overheatingand nuisance
circuit breaker trips. Check the line voltage.
Figure 4.7 Interior anatomy of an HMI head.
Light Fixtures—The Basic HMI Arsenal 81
Problems with Flicker
Flicker is one of the most aggravating problems you can havebecause it can
occur from a number of different causes. Most commonly, it is dueto a bad connection
in the distribution system but may result from a wandering arc inthe globe, improper
voltage, bad power cable connection, or faulty head cable. Anintrepid and dauntless
electrician is needed to track down the actual cause of theflicker.
First, let me stress that we are now talking about visible flicker.It is a common
misconception that a visible “flicker” in the light is cause forconcern about the
generator’s Hertz regulator. Electricians are generally aware that,to avoid flicker,
HMIs require a precisely regulated Hertz rate; however, one mustrealize that this
type of “flicker” is a pulsation recorded on film only—it is notvisible to the eye on
set. (More about this horror later under HMI “Flicker” andFlicker-Free Ballasts.)
Visible, random, intermittent flicker is almost always caused by abad connection
in the distribution system, head feeder, or ballast feeder cable.In the worst
case, a bad contact in the power feeder or distribution cable cancause the light to
stop working altogether. Try to determine if more than one light isbeing affected;
if so, what part of the distribution do they share? Are they on thesame 100-A whip
(maybe a bad Bates plug)? Are they on the same leg (maybe a looseconnection on
that phase)? If a neutral connector is loose in the distribution,all phases flicker.
When using Bates cable, check for loose-fitting pins and hotconnectors and
black pitting on the hot pin of the power feeder. Use your dikes ora pin-splitter to
spread the pins if the pin is squished together. Contact cleaneralso works miracles
to restore dirty pins. When working in dirt, dust, or sand over anextended time, it
is a good idea to give the HMI connectors a cleaning every week orso. Blow out
dirt with compressed air, and clean the pins and receptacles withcontact cleaner.
A visible ongoing pulsation or a flutter in the light is evidenceof a wandering
or unstable arc in the globe. Arc instability may be due to anonhorizontal orientation
of the globe or a defective globe. Double-ended lamps may develop awandering
arc when the inner globe is positioned on a tilt. Arc instabilitymay also be due to
excess current on the electrodes, which points to faulty voltageregulation by the
ballast or improper input line voltage. Excess current wears downelectrodes at an
accelerated pace, aging the globe before its time. Beforediscarding a globe as
unstable, check it by using a different ballast.
The condition of the arc can be checked by viewing the globethrough a
welding glass. Because of the other lights in use, a wandering orfluttering arc may
not be apparent to the eye when looking at the subject onto whichthe light is falling,
but it will register on film. The problem becomes clearly apparentwhen you observe
the arc in the globe. This is harder to do with Fresnels becauseyou cannot see
through the lens very clearly. Do not attempt to view the bulbdirectly.
Momentary spikes or flashes in an HMI, other than during thewarm-up period,
may be an indication that the Hertz rate of the generator isjumping (magnetic ballasts
only). The generator’s frequency meter may not detect very short,erratic frequency
pulses. Measure the current with a frequency meter that has a highsampling rate to
determine if the governor in the generator is faulty.
82 SET LIGHTING TECHNICIAN’S HANDBOOK
HMI “Flicker” and Flicker-Free Ballasts
Standard Magnetic Ballasts
The light intensity of an HMI increases and decreases 120 times asecond,
twice every AC cycle. This fluctuation is not visible to the eyebut is captured on
film as a steady pulsation if the camera is not in precisesynchronization with the
lights. To avoid capturing light pulsation on the filmed image, youmust (1) use a
crystal-controlled camera, (2) run the camera at one of a number ofspecific frame
rates, and (3) use a line current maintained at exactly 60Hz.
The safe frame rates are those that divide evenly into 120 (120,60, 40, 30,
24, 20, 15, 12, 10, 8, 6, 5, 4, 3, 2, 1). Additional HMI-safe framerates at any shutter
angle are listed in the tables in Appendix D. At any of these framerates, the camera
motor must be crystal controlled. A wild or non-crystal-controlledcamera cannot
be used with magnetic HMI ballasts.
Standard ballasts also create light pulsation on film if the ACHertz rate is not
precisely controlled (if, for example, the generator’s governor isout of adjustment).
The Hertz rate for any power line can be checked using an in-linefrequency meter
or by measuring the light’s flicker rate with a photosensitiveCinecheck frequency
meter pointed at the HMI head itself (magnetic ballast only).Rental companies can
supply a frequency meter with their equipment. Additionally, mostgenerators have
built-in frequency meters.
Square-Wave Electronic Ballasts
Square-wave ballasts eliminate the flicker problem. They allow youto film
at any frame rate, at changing frame rates, and with a wild camera(Figure 4.8).
When filming an action sequence—an explosion or a car crash, forexample—
some of the cameras shoot at a high frame rate (slow motion). Togive the DP
the flexibility to choose any speed, the light output from the HMIsmust be flicker
free.
A square-wave ballast maintains a virtually constant output oflight over the
whole AC cycle by squaring off the curves of the AC sine wave. Thechangeover
period is so brief that the light is virtually continuous (Figure4.9C and D).
Unfortunately, the square wave causes the globe, igniter, and otherparts of
the head to make a high-pitched whistle. The head becomes aresonating chamber,
amplifying the noise and projecting it toward the set and themicrophones. To make
the ballasts quiet when recording dialogue, electronic ballasts arefitted with a switch
to change between flicker-free operation and silent operation. Inthe silent mode, a
special circuit electronically rounds off the sharp corners of thesquare wave, which
eliminates the noise (Figure 4.9E).
In the silent mode, a square-wave ballast provides flicker-freelight at frame
rates up to about 34 frames per second (fps), and in flicker-freemode, up to 10,000 fps.
Make sure that all ballasts are set to the same setting.
83
Figure 4.8 Electronic flicker-free ballasts. Power Gems and Arriballasts are constant power
ballasts. Most models are dual wattage with autosensing. Note: Whenballast is operating both
outputs are hot. Cover the unused outlet. On Power Gems (A)18k/12k, (B) 12k/6k, (C) 6k/4k,
(D) 4k/2.5k, and (E) 2500/1200W controls include start and stopmomentary switches, breakers,
dimmer pot, silent/flicker-free selection switch, and liquidcrystal operation/diagnostic display.
The 1200/575W model (F) has a wattage selection switch and separateoutput connectors. Arri
ballasts shown are (H) 12k/6k, (I) 4k/2.5k, and (J) 1200/575W. Arrialso makes DMX-controlled
ballasts in all sizes. (Courtesy of Power Gems, Van Nuys, CA, andArri Lighting, New York.)
84 SET LIGHTING TECHNICIAN’S HANDBOOK
Square-wave ballasts completely process and regulate the inputpower, and as
a result, they offer additional advantages and features,including
• Light weight: A lot less backache than their ship-anchor magneticcounterparts.
• Wide tolerance for voltage and Hertz rate discrepancies:Variation of up to
10% in voltage or line frequency has no adverse effect onoperation.
• “Dimming” capability: By controlling current, the ballast can dimthe lamp
50%, or about one stop of light. At 50% power, a globe’s colortemperature
is 75K–200K higher (bluer) than normal.
• Increased light output (5%).
• Increased globe life (as much as 20%).
In addition, modern constant-power electronic ballasts are able toregulate not
just lamp current but lamp power, enabling the ballast tocompensate for changing
lamp voltage as a lamp ages. Constant power means the lamp has astable, optimal
color temperature that remains uniform regardless of lamp age orline voltage.
Constant-power designs are also less prone to overheating thanconstant-current
ballasts (in situations where line voltage is low, current canbecome excessive).
The more-sophisticated electronic ballasts (like those shown inFigure 4.8) incorporate
warning lights or self-diagnostic messages on an LED display. Aftershutdown,
Figure 4.9 The normal sinusoidal 60-Hz current cycle of a magneticballast (A) creates
a fluctuating light output (B), requiring that the camera framerate be synchronized with the
light fluctuations to obtain even exposure from frame to frame. Therefined square-wave
signal of an electronic ballast (C) creates virtually even lightoutput (D), rendering the fixture
flicker free. The sharp corners of the normal square-wave signalcreate noise in the head.
When operated in the silent mode, the ballast electronically roundsoff the corners of the
square wave (E).
Light Fixtures—The Basic HMI Arsenal 85
the display identifies the problem: an overheated power module,improper input
voltage, a short in the output circuits, current on the groundwire, a misconnected
cable—everything but a readout of the gaffer’s blood pressure. Ifthe ballast shuts
off, be sure to check the display before rebooting theballast.
Most electronic ballasts we use are of European origin and have a50-Hz/60-Hz
output selection switch. This switch controls the timing of theoutput waveform from
the ballast. With these ballasts, the output waveform has noreference to the input
voltage Hertz rate, so it will work with any supply Hertz rate.Normally, this switch
would be set to 60 Hz in the United States (because we normallyshoot at 24 fps);
however, you can use this switch to gain alternative flicker-freespeeds when operating
in silent mode. On the 50-Hz setting, safe frame rates include 100,50, 33.33,
25, 20, 10, and 5 fps. Of course all the HMIs on the set have to beon the same
setting. (Additional safe frame rates with 50-Hz output appear inAppendix D.)
Power Factor Correction Circuits
Power factor is explained in greater detail in Chapter 11, but fornow I’ll offer
a simplified explanation. A purely resistive load (e.g., anincandescent light) has a
power factor of 1.0. Voltage and current increase and decreasesimultaneously in a
sinusoidal waveform, 120 times a second. Volts × amps always equalswatts. The
circuitry in magnetic and electronic ballasts is not purelyresistive; it has other
properties that knock voltage and current slightly out of phasewith one another.
This lowers the power factor. Electronic ballasts with no powerfactor correction
circuit have a power factor of around 0.7, which means the ballastcan use only
70% of the power it draws, or to put it another way, it has to draw30% more power
than it uses: (Volts × amps × pf = watts). This has severalconsequences, none of
them good. It means the generator has to work 30% harder, use 30%more fuel, and
have 30% less capacity available for lighting. It also means theballasts have to work
harder, generate more heat, and age sooner.
A power factor less than 1.0 also means a high return current onthe neutral
wire in the distribution cable, and the neutral wire needs to bedoubled or even
tripled to handle the excess current. With a power factor of 1.0,when the phase
wires (red, blue, and black) are evenly loaded, the current cancelsout between the
phases, and the neutral wire carries only the difference betweenphases. With a
power factor of less than 1.0, the load on each of the phase wiresdoes not cancel
out even when they are evenly loaded. With a power factor of 0.7,for example,
30% of the current does not cancel between phase wires but insteadit adds up on
the neutral. So you would have to carry 90% of the load on theneutral even though
all phase wires are evenly loaded (assuming you have three-phaseservice).
Additionally, some types of ballast electronics also create spikecurrents that
can reach 21/2 times those of the equivalent sinusoidal waveform.This happens
because the capacitors are charging only at the peak of the sinewave. Generator
suppliers complain that this creates extremely high loads on theservice or generator
and can interfere with the generator’s voltage regulator and evenburn out the
alternator. To contend with spike currents, some suppliersrecommend the generator
86 SET LIGHTING TECHNICIAN’S HANDBOOK
be oversized to at least twice the size of the load, when the loadhas a low power
factor. And they warn spikes may also affect other units running onthe same
service.
A power factor correction circuit realigns the waveform and inducesa
smoother waveform. Power factor correction circuits successfullyincrease the power
factor to as much as 0.98. The ballast uses power more efficientlywith minimized
return current and line noise and also reduces heat, therebyincreasing reliability.
Table 4.1 lists power consumption for three prominent makes.
European electrical codes require the use of power factorcorrection with main
power, but it is not required in the United States. Almost allmanufacturers now
include power factor correction on 12k/18k ballasts (for thesehigh-current units,
power factor correction becomes not just desirable but necessary toprotect the
electronics from extremely high currents and overheating). Allmajor manufacturers
offer power factor correction as an option on medium-sizedballasts. However,
because of the added cost, weight, and complexity of power factorcorrection, rental
houses may or may not stock them. The gaffer or best boy mustspecify that power
factor corrected ballasts are required when ordering the equipment.For smaller
lighting setups, power factor correction is usually of noconsequence; however, when
large numbers of ballasts (4k and up) are to be used, power factorcorrection is
advisable. Arri calls their optional power factor correctionfeature an active line
filter (ALF).
Table 4.1 Electronic Ballast Power Consumption
Lightmaker
AC/DC
Lightmaker
AC/DC
B & S
(Arri, Sachtler)
Power Gems
(LTM, Strand, Leonetti)
DC Amps AC Amps AC Amps AC Amps
240-V Input 120-V Input
200 3 A, 120 V 5.1 A, 120 V 1.5 A @ 240 V 3 A @ 120 V
575 8 A, 120 V 10 A, 120 V 9 A, 120 V 5 A @ 240 V
3 A @ 240 V w/pfc
10 A @ 120 V
1200 17 A, 120 V 20 A, 120 V 18 A, 120 V 8.3 A @ 240 V
5.6 A @ 240 V w/pfc
17 A @ 120 V
2500 27 A, 120 V 39 A, 120 V 32 A, 120 V 16 A @ 240 V
11.5 A @ 240 V w/pfc
32 A @ 120 V
4000 42 A, 120 V 56 A, 120 V 52 A, 120 V 25.7 A @ 230 V
18 A @ 240 V w/pfc
51 A @ 120 V
6000 65 A, 120 V 75 A, 120 V 41 A, 120 V 41 A @ 240 V
27 A @ 240 V w/pfc
12,000 120 A, 120 V 145 A, 120 V 81 A, 120 V 80 A @ 240 V
52 A @ 240 V w/pfc
12/18k 61 A/91 A, 240 V 53 A/79 A, 240 V w/pfc
w/pfc = unit with power factor correction.
Light Fixtures—The Basic HMI Arsenal 87
DMX-Controlled Ballasts
Both major ballast manufacturers now offer DMX-controllableversions of
their ballasts. By linking multiple ballasts with a DMX-controlcable and setting an
address on each ballast, you can turn units on and off and dim(electronic ballasts)
to 50% from a central dimmer console. This is a great conveniencewith large
location rigs and in the studio, where dozens of lights are spreadout all over the
perms and throughout the set. Manufacturers offer DMX-controllableballasts in all
sizes 575 W and up and DMX control as a retrofit to electronic andmagnetic ballasts.
These power supplies tend to be sensitive to crosstalk on the DMXcable. Keep the
DMX runs away from the power cables and use an Opti-splitter ifcontrol problems
occur.
Troubleshooting
The development of electronic ballasts with features such asconstant power
output, sophisticated diagnostic and protection circuits, and powerfactor correction
is the result of years of struggle by ballast manufacturers tomaster reliability.
Electronic parts in the older, simpler electronic ballasts weresusceptible to trouble.
For example, repeated hot stabs could burn out the inrush resistorthat protects the
front-end rectifier bridge diodes and capacitors during start-up.The most common
repairs to older electronic ballasts revolved around damage toinput rectifiers, vented
(blown) capacitors, open inrush resistors, or blown power modulefuses—all caused
by high inrush current. To protect the inrush resistor, be sure toturn off the main
on/off switch or breaker after use and make sure it is off beforeplugging in the
power cord.
Another common repair on older ballasts is damage to the outputtransistors
(IGBTs and FETs) caused by a short or arc path in the head or headcable. A shorted
igniter circuit can burn out ballast after ballast. In some cases,the ballast continues
to work even though internal parts are damaged. The result is thatother parts overheat
and short out, and the repair bill and turnaround time keep goingup.
Newer ballasts include back-end protection circuits, so that asensor shuts off
power if it senses a short. This protects the ballast but itdoesn’t lower the blood
pressure of the gaffer, who is waiting for that light to come on.As a precondition
to operation, sophisticated ballasts demand that the head andcables be in good
condition, with no shorts in the power line or ground, and acontinuous ground.
Once an electronic ballast craps out, there is seldom anything youcan do but
replace it. Nothing inside an electronic ballast isuser-serviceable; you have to leave
it to a qualified electronics technician. For this reason,preventative steps become
all the more important. There are many things electricians can doto prevent a failure.
The main one is to treat the equipment as you would any electronicdevice. Electronic
ballasts must be handled gently and thoroughly protected from heat,moisture,
condensation, precipitation, dirt, sawdust, and so on. They cannotbe left baking on
a hot beach or outside overnight in the dew. Magnetic ballasts arejust about
bulletproof, being made mostly of copper and iron. They can takeall kinds of abuse,
both physical and electrical, without failing. Electronic ballastsare made of circuit
88 SET LIGHTING TECHNICIAN’S HANDBOOK
boards, relays, capacitors, and transistors, like your home stereo,and although they
have rugged casings and use heavy, commercial-grade components,electronic ballasts
cannot be treated like magnetic ballasts. The electrician mustenter a solid-state
frame of mind when handling this equipment.
Ballast Electronics
A magnetic ballast is a very simple device. Input power is routedthrough the
main breakers to a choke coil connected between the main input andthe lamp. The
coil may be tapped in several places to provide for various inputvoltages and a high
start-up voltage. Capacitors are also included to compensate forthe inductance of
the coil and restore a unity power factor. The coil provides thestart-up charge for
the igniter circuit, then acts as a choke, regulating current tothe lamp once the light
is burning. Power from the coil is routed to the main contactors(which are controlled
by a low-voltage control circuit) and the igniter circuitwire.
An electronic ballast is quite a bit more complicated (Figure4.10). There
are three primary stages to a square-wave ballast. The first stage,the DC intermediate
circuit, converts power to DC. As a preliminary, power flows fromthe mains
supply through the circuit breakers and earth leakage detectioncircuit to the RF
mains filter. This filter restricts the flow of noise back onto thesupply service.
Contactors K1 and K2 and the start-up resistor form a circuit thatcharges the
Figure 4.10 Block diagram of a 2500-W electronic ballast. (Courtesyof Arri Lighting,
New York, and B & S Elektronishe Gerate GmbH, Germany.)
Light Fixtures—The Basic HMI Arsenal 89
capacitors before the power electronics are activated at start-up.The input rectifier
and capacitors then convert the current to DC: The input rectifierinverts the
negative half of the AC cycle, and the capacitors level it out toone continuous
positive DC voltage.
The second and third stages are referred to as the powerelectronics or power
modules. The second stage is a step-down or buck converter(HF-converter board
and HF-choke) that draws a constant current from the DCintermediate stage, then
precisely regulates current flow to the final power electronics.Actual current flow
is constantly monitored by the control board and adjusted bycontrolling the highfrequency
(20 kHz) duty cycle of transistor T1. This circuit (T1, D1, andHF-choke)
allows a constant power ballast to maintain a lamp at optimum colorand output
performance as lamp voltage increases with age.
The final stage (LF-converter board) serves as an inverter, turningthe DC
current into an AC square wave using four specialized transistors(insulated gate
bipolar transistors, or IGBTs). The IGBTs switch back and forth inpairs (T4 and
T3, then T2 and T5), reversing the polarity at a frequencycontrolled by the control
board. (Frequency is not referenced to the line Hertz rate. Thus,an electronic ballast
is not affected by a generator that is slightly off speed.) Atransformer and voltage
supply board circuit provides power for the control boards.
Whether the ballast is electronic or magnetic, seven wires runthrough the
head feeder to the head (except in some Arri ballasts, which getaway with six):
two (thicker) power wires, VOH (voltage out hot), and VOR (voltageout return); a
ground wire; the igniter’s power line; and three 15-V logic signalwires: switch
common (15 V from ballast), on momentary (a remote on switch at thehead), and
safe on (which is wired to the microswitch in the lens door and tothe off switch on
the head. Both switches must be closed for the main contactors in amagnetic ballast
to close; in the case of an electronic ballast, the power modulesact as an electronic
circuit breaker).
In the head, VOH and VOR run directly to the terminals of theglobe. The
ground wire is connected to the lamp housing. The igniter’s powerline and VOR
are connected to the primary step-up transformer of the ignitercircuit. This transformer
steps voltage up to about 5000 V. From there, current runs througha spark
gap to a secondary transformer, which boosts voltage up to thestarting voltage of
the lamp, on the order of 17 kV. When the operator pushes thestrike button two
things happen: The contactors in the (magnetic) ballast are closed(in an electronic
ballast, the control board turns on the power control circuits,FETs, and IGBTs),
which apply voltage to VOR and VOH, and a 200–350-V strike voltageis sent to
the head on the igniter power line.
Taking it in extreme slow motion, the strike sequence happens asfollows:
The ignition voltage climbs from zero, increasing until the voltagepotential is
sufficient to bridge the spark gap. When a spark bridges the gap, avery high-voltage
start charge is delivered to the electrodes of the lamp from thesecondary transformer.
After 1–11/2 seconds, a timer circuit removes igniter power fromthe circuit. Once
the flow of electrons is initiated in the bulb, the ballast startsto hold back current.
The lamp arc stabilizes and voltage rises to the normal operatingvalue.
90 SET LIGHTING TECHNICIAN’S HANDBOOK
The spark gap is set to deliver the proper strike voltage for thebulb. To some
extent, increasing the spark gap can improve hot restrikecharacteristics because it
increases strike voltage; however, adjusting the spark gap involvesspecial tools and
an experienced technician—the parts are fragile and extremelysmall. Too narrow
a gap produces insufficient voltage to arc the bulb; with too widea gap, the voltage
does not bridge the spark gap.
The lamp is turned off when the “safe on” line is interrupted, byeither the lens
door microswitch or the off button on the head or ballast. Thisopens the main contactors
in a magnetic ballast or shuts off the power control circuits in anelectronic ballast.
DCI Lamps and Ballasts
Direct current iodide (DCI) lamps were introduced in 1993 by L.P.Associates.
Like a xenon bulb, a DCI lamp uses DC current. It creates aconstant, flickerless
light and therefore has no light pulsation problem. DCI lamps havemany of the
same characteristics as HMIs: 5600-K color temperature, cooloperating temperature,
high luminous efficiency, bright light output, and hot restrikecapability. DCIs have
a dimming capability, like HMI electronic ballasts, but unlikethem, DCIs operate
silently and are flicker free at any frame rate. DCI lamps are madein sizes from
500–10,000 W that match the dimensions of corresponding HMI lamps:750 or
1,000 DCI (575 HMI), 1,500 DCI (1,200 HMI), 3,000 DCI (2,500 HMI),5,000 DCI
(6,000 HMI), and 10,000 DCI (12,000 HMI). With a simplemodification to the
lamp holder, standard HMI fixtures can use DCI lamps by operatingon a special
DCI power supply. The small, lightweight power supplies take ACinput power and
deliver DC power to the lamp. On L.P. Associates’ 750- and 1500-Wfixtures there
is no separate ballast and feeder cable; the power supply andigniter are built into
the housing on the base of the light.
Operating characteristics, such as lamp warm-up time, the need forcare in
handling and cleaning the lamp, lamp installation with nipplepointed forward, the
use of UV emission safeguards, and lamp life (200–300 hours), arethe same as for
standard HMI lamps. Unlike HMIs, DCI lamps have a positiveelectrode (anode)
and a negative electrode (cathode). Installing the lamp withcorrect polarity is critical
to proper operation; therefore, the diameter of the positive end isslightly larger,
requiring that one lamp holder on a standard HMI fixture beenlarged for use with
a DCI lamp. To prevent an AC ballast from being connected to a DCIlamp, the
feeder cable connectors are also different.
Like other electronic power supplies, DCI ballasts have a fairlylow power
factor, and with 120-V ballasts there is return current on theneutral.
Three-Head, Three-Phase Solution
One way to get around the HMI pulsation problem when operating atoff
speeds or with a wild camera and magnetic ballasts is to use threestandard HMI
ballasts connected to three heads, each powered from a differentleg of a three-phase
source. Because the three phases peak a third of a cycle apart,when taken together,
Light Fixtures—The Basic HMI Arsenal 91
the three lights have an actual frequency of 360 peaks per second(3 × 120 = 360).
At this frequency, the camera does not detect the pulsation (Figure4.11).
The lights must be bounced or mounted close together and placed farenough
from the subject not to create separate shadows. The light createdis flicker free at
any frame rate.
HMI-Type Lamps
HMI (Hg [mercury] medium-arc iodide; Osram), HMI/SE (singleended;
Osram), MSR (medium source rare earth, single ended; Philips), GEMI(General
Electric metal iodide), CID (compact indium discharge; Thorne, UK),CSI (compact
source iodine; Thorne, UK),2 DAYMAX (made by ICL), and BRITE ARC(Sylvania)
are trade names of lamps in the HMI family registered by thevarious manufacturers.
All these consist of two tungsten-coated electrodes surrounded bymercury vapor
and other metal halides held in a quartz envelope. The flow ofelectrons switches
electrons in the gas from one highly excited state to another,releasing energy in the
form of visible and UV light. While the mercury is responsible formost of the light
output, an optimal mix of halides of rare earth metals in themercury vapor brings
a balance of color output. The result is a quasi-continuousmultiline spectrum,
meaning that the color is made up of narrow peaks of variouswavelengths rather
than a continuous spectrum, which closely resembles the makeup ofdaylight and
renders colors faithfully on film. There are two kinds of HMIglobes: single ended
and double ended (Figure 4.12).
Single-Ended Globes
The design of single-ended (SE) globes allows for greatly improvedefficiency
when mounted axially and used with a bright reflector, as in SEPAR
fixtures. They are also used mounted vertically in some models ofFresnel fixtures.
Figure 4.11 With three-phase power, the peak of each leg is a thirdof a cycle out of
sync with the last, creating six peaks in each cycle. At 60 Hz,that amounts to 360 peaks per
second, which is a high enough frequency to be flicker free at anyframe rate.
2CID and CSI are used in stadium lighting. CID is also used insmall sun-gun fixtures and has
the same color characteristics as HMI globes.
92 SET LIGHTING TECHNICIAN’S HANDBOOK
Single-ended globes of 575 W and larger can generally be burned inany orientation.
The design and short overall length of SE globes make it easy forthem to
restrike while hot.
Double-Ended Globes
HMI Fresnels and soft lights use double-ended globes. The range ofsizes is
shown in Figure 4.12. Double-ended globes of 4k and larger must beburned with
their arc within 15° of horizontal; never tip these larger HMIs ontheir side.
Figure 4.12 HMI globes. (Courtesy of Osram Corp., Van Nuys,CA.)
Light Fixtures—The Basic HMI Arsenal 93
Relamping HMI Heads
Before relamping a light, be sure that the breakers are off, thefixture is
unplugged, and the lamp is completely cooled. HMI bulbs build upinternal pressure
when in use. It is dangerous to handle them when hot; if broken,they will explode,
sending shards of hot quartz in all directions.
The golden rule when relamping any fixture is never to touch thequartz
envelope with your fingers and never to allow moisture or grease tocome into
contact with the bulb. Even a light smudge of finger grease causesa hot spot on the
quartz envelope, which weakens the quartz and causes the envelopeto bubble. When
the globe loses its shape, the globe’s photometric and structuralproperties are
compromised and the globe could explode. HMI globes are tooexpensive to handle
carelessly. At this writing, a single-ended 12k HMI globe is pricedat around $2299.
When an HMI globe explodes, it shatters the lens and destroys thelamp holder and
reflector, bringing the total loss to a staggering sum. Alwayshandle globes with a
clean and dry rag, with clean cotton gloves (editor’s gloves), orwith the padding
in which the globe is packed. Make it a practice to clean the globeonce it is mounted
in the fixture. Use a presaturated alcohol wipe or isopropylalcohol and a clean lintfree
tissue.
Double-ended HMI globes have metal ends that are laid into the lampholder.
HMIs of 2500 W and larger have clamps that close around the globeends and are
tightened with a screw. Finger screws, Allen screws, nuts, orstandard screws are
used. HMI globes of 6k, 12k, and 18k have connection wires thathave to be attached
to terminal screws on the base of the lamp receiver. Globes of 575and 1200 W are
held in a U-shaped receiver. Their ends are threaded and aretightened in place with
knurled nuts. The 200-W globe has a knife plug, a flat tab thatslides into the
connectors on the base, and is locked in place with tighteningscrews.
Insert double-ended globes into the fixture with the molybdenumribbon horizontal
so that it does not block light returning from the reflector(Figure 4.13).
Figure 4.13 Proper installation of an HMI globe. Note that theribbon is horizontal and
the nipple is oriented outward (it may also be oriented upward).Connections are tight. HMI
globes should be cleaned with an alcohol-impregnated cloth as apart of daily maintenance.
94 SET LIGHTING TECHNICIAN’S HANDBOOK
Orient the nipple on the bulb upward or outward toward the lens,not downward
or toward the reflector. The nipple should always be above the arcto prevent a cold
spot from forming where chemicals in the globe enclosure maycondense and
interfere with the burning cycle.
Be sure the globe’s contact pins are tightly secured in place.Contamination
in the contacts or a loose contact will impair proper cooling. Abad contact, evidenced
by pitting and discoloration on the contact pins, causes prematurelamp failure. A
loose HMI globe may also vibrate.
With some SE PAR fixtures, it is impossible to install or removethe globe
without handling it by the glass. Great care must be taken to avoidbreaking the glass
where it attaches to its ceramic base. Hold the glass with a cleanrag, and wiggle the
globe gently along, not across, the axis of the pins; any stressacross the axis can
very easily snap the quartz. The better single-ended PAR fixturesprovide a globe
release. When the knob is loosened, the globe can be inserted andremoved with ease.
HMI Lamp Characteristics and Hazards
Color Temperature
Factors that affect the color output of HMIs are the type of globe(5600 K or
6000 K), the number of hours the globe has been used, lamp cooling,and the regulation
of the power by the ballast. It is good practice, especially withHMIs larger than
2500 W, to match heads to ballasts and number and label both thehead and the ballast
with the color temperature and the amount of green that the lightemits. For example,
a head and ballast would be labeled “#1, 5500 K, +2, 5/13/96.” Thisindicates ballast
1, which is matched to head 1, 5500 K color temperature, has a +2CC of green on
the date shown.
Globe Life
When an HMI globe is brand new it often shows a very high colortemperature
(10,000–20,000 K). This is sometimes accompanied by some arcinstability, causing
flicker. You may want to “burn in” the globe before filming starts,or color correct
the lamp. During the first couple hours of use, the colortemperature comes down
quite quickly to the nominal value (5600 K or 6000 K) and the arcstabilizes.
Thereafter, the color temperature changes over the life of theglobe at the rate of
0.5–1 K per hour, depending on conditions. The color temperaturedecreases because
as the gap between electrodes increases, more voltage is requiredto maintain the
arc, and as the voltage increases, the color temperature decreases.For safety reasons,
manufacturers recommend that globes not be used for more than 125%of their rated
service life. As the bulb ages, changes in the quartz glassenvelope make the globe
increasingly fragile.
Lamp Cooling
You can overheat a lamp and cause damage to the reflector or lensby pointing
the lights at an extreme up or down tilt. Also, if the lightreceives inadequate
ventilation, the color temperature shifts toward green andblue.
Light Fixtures—The Basic HMI Arsenal 95
Ultraviolet Emissions
All HMI globes produce light that has harmful amounts of UVradiation. Skin
and retinal burns can result from direct exposure to the light. Forthis reason, a
special housing and protective lens must be used. UV rays arereduced to a safe
level when the light passes through the glass lens or when thelight is indirect,
bouncing off the inside walls of the fixture, for example. HMIsalways have a safety
switch that shuts off the globe if the lens door is opened or ifthe lens breaks. You
can get a nasty burn very quickly by tampering with these safetyfeatures or by
using broken or homemade equipment that doesn’t have them.
A damaged or poorly made fixture that leaks direct UV radiationcan, and
has, caused skin burns, retinal burns, and even skin cancer. Ifprolonged proximity
is unavoidable, as when operating a 12k in a condor, and you startto feel some
burning on your skin, place a flag to block radiation from thefixture and have the
fixture replaced ASAP.
Mercury
HMI globes contain very small amounts of mercury, which ispoisonous. If a
globe breaks, take sensible precautions to prevent ingestion oftoxic chemicals. Keep
chemicals off your hands. Wash your hands. Dispose of broken andburnt-out bulbs
in an appropriate place. Normally, burnt-out globes must bereturned to the rental
house for inventory.
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97
CHAPTER 5
Fluorescent Lights
History of Fluorescent Lights
Until relatively recently, cinematographers regarded fluorescentlighting as a
minefield of photographic headaches, virtually incompatible withmotion picture
photography. Fluorescents were associated with ghoulish green skintones, poor
color rendering, anemic light output, noisy humming ballasts, andthe same shutter
speed restrictions that existed with HMIs (with magneticballasts).
In the 1980s, confronted with the inevitable need to shoot influorescent environments,
many gaffers started putting together their own fluorescentsystems. They
wired newly available solid-state ballasts to kluged lampharnesses, and sought out
new commercially available tube designs that provided a bettercolor spectrum. A
range of fluorescent color correction gels were developed forfluorescent lights. The
results rendered fluorescent environments filmable, but colorbalance and light output
were still far from ideal.
It took the innovations of a determined gaffer and his best boy toovercome these
obstacles. Freider Hochheim and Gary Swink designed fixtures,ballasts, and lamps
tailored to the needs of film production. Their company, Kino Flo,Inc., continues to
make groundbreaking advances in the photographic applications offluorescent technology.
Various manufacturers now offer stand-mounted fluorescent fixtureswith highfrequency,
flicker-free ballasts (Table A.10), which operate with commerciallyavailable
lamps. Kino Flo makes its own lights, which are high output andcolor corrected (Table
A.11). Cinematographers discovered the positive qualities offluorescent lights: lightweight
fixtures that put out soft, controllable light that wraps aroundthe features and
creates a pleasing eye light. They can easily be built into setswhen a fluorescent
environment is called for and can be used purely as a low profile,soft lighting instrument.
Kino Flo
Kino Flo makes fluorescent lighting systems specifically for filmproduction
work (see Table A.11, Appendix A). Kino Flo tubes are speciallydesigned to be used
with Kino Flo high-output ballasts. The Kino Flo KF55 (5500 K),KF32 (3200 K),
98 SET LIGHTING TECHNICIAN’S HANDBOOK
and KF29 (2900 K) broad-spectrum fluorescent lamps are engineeredto correspond
to the spectral sensitivity curves of color film emulsions. KinoFlo tubes mix wideband
and narrowband phosphor crystals with rare earth elements. Thephosphor blend
displays a complete spectrum of light (Color Rendering Index of 95)and no green
spike when operated with Kino Flo high-output ballasts. In AppendixE, Table E.2
lists all Kino Flo tubes and Figure E.1 illustrates the differenttube types. Kino Flo
also makes green and blue tubes specifically suited forgreen-screen and blue-screen
work. Matte photography is discussed in detail in Chapter 10. Red,pink, yellow,
and UV (black light) tubes are also available, which are great fordecorating a set
with neonlike lines of light. All Kino Flo tubes are safety coatedto make the lamps
more durable and ensure that no glass fragments, mercury, orharmful phosphors
are released if the lamp breaks (Parts are shown in Figure5.10D).
Kino Flo ballasts run at high frequency (most at 25 kHz, theDiva-Lite at
>30 kHz), resulting in flicker-free operation at any frame rateor shutter setting. The
lights turn on instantly, even when cold, requiring no warm-uptime. Kino Flo
ballasts provide switches for individual lamps or pairs of lamps,so controlling
brightness is a simple matter of adding or subtracting lamps. Theycan also be
dimmed about one stop on a variac dimmer, or better still, using aKino Flo dimming
ballast you can reduce output to 3% without flicker. (You cannotuse an electronic
SCR dimmer or household resistance-type dimmer with a fluorescentlight.) Kino
Flo ballasts are lightweight and run silently.
Kino Flo 120-V Systems
Detailed, up-to-date information can be found on Kino Flo’swebsite. See
Appendix H for web addresses.
Portable Fixtures
Kino Flo fixtures come in various configurations and sizes. Thefour-bank
systems, double-bank systems, and single-bank systems each havetheir own corresponding
ballast and head cable (Figure 5.1). Each fixture is equipped witha
lightweight egg-crate louver that controls the spread (and slightlyreduces the intensity)
of light. The fixture has a snap-on mounting plate for attachmentto a C-stand
(Figure 5.2), but because the fixtures are lightweight, they canalso be taped or
stapled into place.
The most commonly used Kino Flo fixtures for lighting on sets arethe versatile
4-ft and 2-ft units. The four-bank, 4-ft units provide sufficientoutput to serve as key
light at moderate light levels, or as a soft fill at higher lightlevels. The double-bank
and single-bank fixtures are handy for hiding in sets, to glow abackground wall or set
dressing. The small fixtures are perfect to light actors close tothe fixture; the fixture
might be attached to a nearby wall, propped hidden behind a TV, orbuilt into the set.
Diva-Lite
The Diva-Lite 400 (four-bank) and Diva-Lite 200 (double-bank)fixtures
(Figure 5.3) are designed with compactness and portability in mind.The ballast is
in the head and can be dimmed its full range using a knob on theback. The fixtures
Fluorescent Lights 99
Figure 5.1 The Kino Flo four-bank, 4-ft fixture, here as part of akit with two fixtures,
Select ballasts, head cables, baby stand mounting plates, andtraveling case. (Courtesy of
Kino Flo, Inc., Sun Valley, CA.)
Figure 5.2 The removable mounting plate. (Courtesy of Kino Flo,Inc., Sun Valley, CA.)
100 SET LIGHTING TECHNICIAN’S HANDBOOK
use a lollipop attachment that adapts directly to a standard babystand. Diva-Lites
utilize the U-shaped compact fluorescent lamp (CFL). The Diva-Lite400 is as bright
as a 4-ft, four-bank fixture. Because of its brightness and handydimming feature,
it is a good head for use as an obie light over or under the cameralens or as a soft
key. The Diva-Lite 400 is available with an optional universalballast, which can
be used around the world on any current source (100-V AC–265-V AC,50/60 Hz).
Flathead 80
The Flathead 80 is a 4-ft, eight-bank fixture capable of puttingout quite a bit
of light (60 foot-candles at 10 ft) while remaining lightweight (26lb) and less than
5-in. deep (Figure 5.4). It is a good light when you must tuck oneagainst a wall
and light a relatively large area. The Flathead 80 employs a pairof Select four-bank
ballasts, so it can be controlled two tubes at a time (in a centerout pattern). It comes
with a parabolic silver louver that controls the spread anddirection without cutting
too much light output. Cardholders at the corners allow theelectrician to fabricate
Figure 5.3 Diva-Lite four-bank and two-bank fixtures use integraldimming ballasts and
high-output lamps. (Courtesy of Kino Flo, Inc., Sun Valley,CA.)
Fluorescent Lights 101
Figure 5.4 (A) The Flathead 80 fixture is lightweight and has highoutput (eight lamps).
The head is connected to two Select ballasts. Card-holders at thecorners (B) enable the easy
use of extension doors. The detachable mounting plate (C) swivelsin all directions and locks
with a knob. The mounting plate pictured fits 11/8-in. juniorreceiver. (Courtesy of Kino Flo,
Inc., Sun Valley, CA.)
102 SET LIGHTING TECHNICIAN’S HANDBOOK
foamcore barn doors in custom shapes and dimensions and attach themwith grip
clips. This is an especially useful feature when trying to controlspill or get a very
even light level (e.g., when lighting a green screen).
Wall-O-Lite
The Wall-O-Lite is a bright, DMX-controllable fixture with integralballast. It
houses 10 4-ft lamps, giving it an output of as much as 75foot-candles at 10 ft (about
as much light as a 2.5 HMI Fresnel bounced) and a weight of 48 lb(Figure 5.5).
Because it creates a broad, even light and is DMX controllable(on/off control from
1 to 10 tubes) (Figure 5.10C), this fixture has proved especiallyuseful for lighting
matte screens (green screens or blue screens). Up to 512Wall-O-Lite fixtures can
be daisy-chained together. Stacked or positioned side by side, theyhave been enlisted
to create a seamless wall of light for special set pieces orspecial effects. The fixture
is also useful as an area light or Northlight. It mounts on ajunior stand.
Blanket-Lite 6 × 6
The Blanket-Lite is composed of 16 6-ft lamps hung in a 6-ft squarearrangement
on a fabric base. A silver fabric reflector is mounted behind thetubes (Figure 5.6).
The light can be hung in a frame or mounted to a wall. The frame,which is 80-in.
square, provides for the attachment of diffusion. The whole thingis only 10 in. deep.
Figure 5.5 Wall-o-Lite’s ballast is on board and can be DMXcontrolled. (Courtesy of
Kino Flo, Inc., Sun Valley, CA.)
Fluorescent Lights 103
It can be used as an overhead soft light or mounted on stands as alarge soft key.
It puts out 137 foot-candles at 10 ft. The Blanket-Lite weighs only30 lb. The frame
weighs an additional 60 lb.
Studio Fixtures
The Kino Flo studio fixtures (Image 80, 40, and 20) are designedfor studio
applications and green- and blue-screen work. They are DMXcontrollable, yoke
mounted with metal housings, metal barn doors, and built-inballasts. The Image 80
(4-ft) has eight tubes, the Image 40 (4-ft) has four tubes, and theImage 20 (2-ft)
also has four tubes.
12-V DC Kits: 12-V Single, Mini Flo, and Micro Flo
Kino Flo makes a variety of 12-V DC fixtures that can run onbattery power
or a 12-V transformer power supply (120-V AC or 220-V AC).
12-Volt Single
In a car, helicopter, or elevator, where AC power is unavailable,you can run
any of the standard Kino Flo fixtures from a 12-V DC battery. The12-V single
ballast can power T-12, T-10, or T-8 lamps, ranging in size from 15in. to 4 ft. Four
12-V ballasts can power a four-bank 4-ft fixture—all that isrequired is a single to
four-bank combiner (see Figure 5.10F). For greater powerrequirements in remote
situations, you can also use an inverter system, described inChapter 13.
With the proper adapter cables, you can power a standard four-bankfixture
from four 12-V ballasts. The 9-in. or 15-in. lamps are ideal in anighttime car scene
to give the appearance of dashboard light. Kino Flo makes 12-V “carkits” with
either 15-in. or 9-in. single-tube fixtures, dimmable ballasts, allthe usual accessories,
cigarette lighter connector, and spring clamps to connect to a carbattery.
Figure 5.6 The 6-ft
× 6-ft Blanket-Lite suspended in a frame with diffusion and asoft
crate to control spill. (Courtesy of Kino Flo, Inc., Sun Valley,CA.)
104 SET LIGHTING TECHNICIAN’S HANDBOOK
Mini-Flo and Micro-Flo
The 12-V Mini-Flo kit has a 9-in. lamp with a correspondingfixture, ballast,
and head cable (Figure 5.7). The Micro-Flo kit consists of tiny6-in. and 4-in. tubes,
thinner than a pencil (either tungsten or daylight) (Figure 5.8).Their size makes
Figure 5.7 12-V DC Mini-Flo kit: Two 9-in. fixtures, mountingplates, and armature wire
to mount the light in any position, 12-V DC ballasts, cigarettelighter adaptor, and clip-on
car battery cables. (Courtesy of Kino Flo, Inc., Sun Valley,CA.)
Figure 5.8 A 9-in. Mini-Flo (reflector and doors removed) and 4-in.Micro-Flo tube Kino
Flo lights. (Courtesy of Kino Flo, Inc., Sun Valley, CA.)
Fluorescent Lights 105
them uniquely suited for many special applications, such as tolight a face inside a
space suit helmet. They are commonly used for tabletop andminiature photography.
Using Kino Flo Fixtures
The components of each fixture (fixture with barn doors, reflector,egg-crate
louver, lamp harness, and tubes) can be disassembled and employedin any number
of configurations as needed (Figure 5.9). The fixture can be usedwith or without
the egg-crate louver. For greater control of the spread of light,combiner clips can
be used to stack several louvers on the same fixture. The spread isreduced to 67
°
with one louver, 37
° with two, and 25
° with three. On the other hand, if a softer,
less-controlled light is wanted, the reflector can be removed,leaving the white
backing as a soft bounce.
The fixture is designed so that, if the whole fixture is too bulkyfor a particular
application, the tubes, wiring harness, and reflector can bequickly stripped out of
the fixture. Bare tubes might be taped under a bar counter, forexample. You can
increase the brightness of bare tubes by taping the reflector tothem. Bare tubes can
be neatly mounted to a surface using plastic cable ties andadhesive cable tie mounts
(and staples if necessary, Figure 5.10G) or by applyingdouble-stick tape to the tube.
You can order a special Y-splitter (Figure 5.10E, F), which splitsa four-bank
(or two-bank) cable into single harnesses, so you can mount tubesend to end, for
example. Be sure to order additional single harnesses and cableswith the splitter.
Figure 5.9 The components of the portable Kino Flo fixtures. Thetubes can be used with
or without the fixture, the reflector, and louver. The lamp harnessuses a simple spring-loaded
locking connector. The mounting plate pops on and off quickly usingplastic locking pins.
No tools required. (Courtesy of Kino Flo, Inc., Sun Valley,CA.)
106 SET LIGHTING TECHNICIAN’S HANDBOOK
Ballasts
With all fluorescent ballasts it is important to connect thefixture to the ballast
before the ballast is turned on, or the electronics will suffer.Newer Kino Flo ballasts
have circuits to protect the electronics from this problem, butmany ballasts do not.
Kino Flo standard ballasts (four-bank, double, and single) provideeither a threeposition
toggle selection switch (all lamps/off/half the lamps) orindividual switches
for each tube. Kino Flo Select ballasts (four-bank, double-bank,and single) feature
an additional high-output/standard-output toggle switch. Use thehigh-output setting
for 4-ft lamps and the standard setting for 2-ft and 15-in. lamps.Operating 2-ft and
15-in. lamps in the HO setting raises the color temperature andgreen output. The
Select ballast also features more advanced electronics than thestandard ballast,
which makes its performance more reliable and consistent.
Kino Flo dimming ballasts (double-bank and single) feature a sliderto adjust
light output in a full range with no change in color temperature. Atrim adjustment
allows you to set and return to a particular setting easily and toturn the lamp on at
a preset level. Dimming ballasts provide a jack for attachment of aremote cable.
Multiple dimming ballasts can be wired to and controlled by astandard dimmer board.
Mega-Flo Fixtures
Kino Flo makes 8- and 6-ft Mega-Flo systems that run on high-outputmegaballasts.
Double- and single-bank fixtures are available. The megaballastsalso power
the Blanket-Lite.
Troubleshooting
From time to time, one or more tubes in a fixture will not light.The problem
could be in the ballast, the lamp harness, or the lamps. The bestway to proceed is
as follows:
1. Double check that the ballast is plugged into live 120-V ACservice.
2. Check that the extension is properly connected at the ballastand harness.
3. Check that the harnesses are properly secured to the tubes andthe head cables
are fully connected at both ends. Harness connectors are colorcoded; the same
color must be on both ends of the lamp.
4. Switch the ballast to full on position. Note which lamps do notwork, and try
another ballast. If the same lamps still do not fire, change thoselamps. If the
lamps still do not fire, change the harness.
When renting four-bank Kino Flos in large numbers, it is prudent toinclude
a few extra backup four-bank ballasts (1 for every 12 systems). TheKino Flo Select
ballasts have a latch-up feature to protect the solid-statecircuitry from abuse during
operation. However, many older ballasts are still in circulation.Single and double
systems generally do not require backup ballasts.
Kino Flo portable fixtures are made with wire barn door “hinges”(the flexible
metal rods at the corners of the doors), which are made to bedisposable. If one
breaks, it can be easily replaced by removing the end screw,pulling out the broken
wire, and replacing it with a length of good wire (Figure5.10I).
107
Figure 5.10 (A) “Flosier” diffusion on a Diva Lite. (B) Velcostraps hold the Foto-Flo
ballast to a four-bank fixture. (C) Dimmable DMX-controlledballast. (D) Kino tubes are
sealed in plastic tubes for safety. These parts can also bepurchased. (E) Four-bank to single
splitter—it allows four tubes with single harnesses to be connectedto a four-bank ballast.
(F) Single to four-bank combiner—it allows four 12-V singleballasts to power a four-bank
fixture. (G) Adhesive mounts and releasable ties, handy formounting bare tubes (you can
also staple the plastic mount if the adhesive doesn’t hold). (H)Harness connector. (I) Barn
door wire repair kit. (Courtesy of Kino Flo, Inc., Sun Valley,CA.)
108 SET LIGHTING TECHNICIAN’S HANDBOOK
Building a Film-Friendly Fluorescent System
from Commercially Available Parts
High-Frequency Ballasts
High-frequency ballasts bypass the problem of intensity fluctuationby converting
a 60-Hz input frequency to between 20,000 and 40,000 Hz. The periodof
time between the off and on pulse of each cycle is so short thatthe illuminating
phosphors do not decay in light output. The phosphors areessentially flicker free.
Some off-the-shelf fluorescent electronic ballasts have anotherflicker problem,
called an ersatz ripple. Even though the ballast puts out ahigh-frequency cycle,
that cycle can start to have a waveform itself. In a number ofincidents, 24p video
cameras and film cameras operating within a flicker-free windowhave picked up
flicker from architectural lights operating near the filming area.Some ballasts simply
are not designed to remove this ripple. In some instances, theballast was found to
be faulty. When shooting on constructed sets, using solid-statehigh-frequency
ballasts for built-in fluorescent light fixtures, it is worthwhileto shoot a test with
the ballasts you will be using. On location, solid-state ballastsare the norm in any
modern installation. Older installations may not havehigh-frequency ballasts and
therefore are limited to fewer shutter speeds and shutterangles.
Color-Correct Fluorescent Tubes
Until recently Duro-Test manufactured standard tubes suitable forcolor photography,
Optima 32 (3200 K) and Vita-Lite (5500 K). Unlike those of othercommercial
manufacturers, these tubes incorporated wideband phosphor crystalsand produced
close to correct color rendering. When filming in a location withceiling fluorescents,
the lighting crew would typically replace all the existingfluorescent tubes with colorcorrect
tubes. Duro-Test is now out of business; at this writing, it is notknown if
another manufacturer will offer the Optima phosphors under a newname.
Note: Tubes like Optima 32s, which have very little green whenpowered by
a conventional ballast, require magenta correction when poweredwith a Kino Flo
high-output ballast. High-output ballasts overdrive the fluorescenttube, which raises
the color temperature and green output.
Some Additional Notes about Fluorescent Lights
Effect of Temperature
Fluorescent lamps are sensitive to extremes of temperature.Standard fluorescents
are designed for operation above 50
°F. Fluorescents operating on highfrequency
ballasts operate in temperatures below freezing. With allfluorescents,
even those operating on high-output ballasts, the operatingtemperature affects both
the color and the intensity of the light. Under freezingconditions, the high-intensity
ballast can get the tube started, but it takes a few minutes forthe tube to reach the
proper color and output. In hot temperatures or if the tubes areenclosed in an
unventilated space, the color may wander toward the blue-green endof the spectrum,
and additional color correction may be needed.
Fluorescent Lights 109
Effect of Voltage Shifts
Voltage shifts do not appreciably affect the color temperature offluorescents.
If the voltage is too low, however, the light will go outcompletely or will not start.
A 10% decrease in power will yield a 10% decrease in lightoutput.
Calculating Power Needs
Fluorescent lights are generally of nominal wattage and thereforepose no
special power demand concerns. However, when a large number(hundreds) of
fluorescent lights are to be powered, one must keep in mind someadditional factors.
The wattage rating on a fluorescent tube is the power consumed bythe tube alone.
The ballast typically consumes an additional 10–20%. Therefore, a40-W tube
actually consumes as much as 48 W of power (20% of 40
= 8, 40
+ 8
= 48). In
addition, the power factor must be taken into account (reactivecurrent and the power
factor are explained in Chapter 11).
This Page Intentionally Left Blank
111
CHAPTER 6
Stands and Rigging
We constantly need to hang lights in awkward places, so naturally,over the
years, ways have been devised to secure a light almost anywhere.People are constantly
inventing and reinventing these devices. The basics are describedin this chapter but
check manufacturers’ websites for up-to-date information (Arri,Matthews, Norms,
American, Modern Studio Equipment, Versales).
Stands
Stands come in two basic types: babies and juniors. Baby stands(sometimes
called 750 stands) have a 5/8 -in. pin that fits into the babyreceiver found on the
smaller lights, baby-2k or smaller (Figure 6.1A).
Junior stands (sometimes called 2k stands) have a 11/8 -in.receiver that takes
the junior pin found on larger lights. Stands of both types come inshort, “low-boy”
versions as well as the standard height with two or three risers.Stands may be made
of aluminum, which is lightweight, or steel, which isstronger.
Baby Stands
The most versatile baby stand for location work is a steelthree-riser stand
with a mountain leg (Figure 6.2). The legs can be quickly retractedby loosening
the T-handle on the top collar and pulling up. The legs have a widebase for stability,
and the mountain leg makes it easy to level the stand when it isplaced on uneven
ground, on a stair, over the edge of a curb, or leaning against aset wall (Figure 6.2).
Rolling Stand
Baby rolling stands are convenient when working in the studio on alevel
surface. Many rolling stands have brakes that snap into a lockedposition.
Blade Stand
Blade stands are extremely lightweight, which is their oneadvantage. They
are also somewhat flimsy and unstable. They are best used withsmall lights. Stabilize
a lightweight stand by hanging a small shotbag on the lowerT-handle.
112 SET LIGHTING TECHNICIAN’S HANDBOOK
Figure 6.1 To retract the legs of most stands, loosen the uppertie-down knob and
pull the legs up and in. With some stands, the legs retract byloosening the bottom tie-down
knob and sliding that collar upward. A 5/8 -in. baby pin insertsinto the receptacle on a fixture
(A). When mounting the light, the pin should be flush with thereceptacle and not stick
through. This assures that the T-handle engages the indent of thepin (B). Also some lights
(notably the baby junior) do not tilt properly if the pin sticks(C).
Stands and Rigging 113
Low Stands
When you need a light placed low, a mini-baby (22–50 in.) orpreemie (31–70
in.) stand comes in handy. Table 6.1 lists the basement and topfloor for many
common stands.
Junior Stands
Combo
The junior combo stand is so named because it was designed tohandle both
lighting units and reflector boards. Larger fixtures, Studio 2k andlarger, have a 11/8 -
in. junior pin. A typical two-riser combo has a maximum height of11 ft. A threeriser
combo has a maximum height of 14 ft. Figure 6.3 illustrates thejunior stand
and some common stand accessories: the baby pop-up pin, the angleddrop-down
offset, and the baby pin adapter.
Low Boy
The minimum height of a typical combo stand is 48 in. If the lightmust be
lower than that, you need a low-boy junior stand, which has aminimum height of
around 33 in. If you need to mount a light lower than 33 in., youhave to underhang
the light from an offset or use a turtle stand or T-bone.
Figure 6.2 Alternative stand configurations.
114 SET LIGHTING TECHNICIAN’S HANDBOOK
Table 6.1 Stands
Name Type Risers
Minimum
Height
Maximum
Height
RM
Leg Brand
Low Baby Stands
Low blade stand Al 2
151/4 "
387/8 " Mole
Mini preemie St 2 20" 39" Matthews
Preemie baby Al 2 31" 5' 10" Matthews
Mini baby St/Al 2 22" 50" X American
Low low baby Al 2 20" 3' 3" Norms
Low hefty baby Al 2 33" 5' 7" Norms
Baby Stands
Steel maxi St 3 34" 10' Matthews
Beefy baby standard Al 2 37" 8' 3" Matthews
Beefy baby, 3-riser Al 3 45" 12' X Matthews
Baby, 2-riser St/Al 2 40" 9' 4" X American
Baby, 3-riser St/Al 3 44" 12' 5" X American
Baby light, 2-riser Al 2 44" 9' 4" Norms
Baby light, 2-riser St 2 52" 10' 6" Norms
Hefty baby, 2-riser Al 2 47" 9' 10" X Norms
Hefty baby, 3-riser Al 3 50" 12' 10" X Norms
Low Junior Stands
Runway base only 0 11" 11" Matthews
Low boy St 2 33" 6' 9" X Matthews
Low boy Al 2 37" 6' 9" X Matthews
Low combo, 1-riser St 1 29" 4' 0" X American
Low combo, 2-riser St 2 32" 5' 6" X American
Low combo, 2-riser St 2 33" 5' 7" X American
Low boy 2 36" 5' 8" X Norms
Rolling folding stand St 1 221/4 " 32" Mole
Junior Stands
Combo St 2 48" 11" X Matthews
Sky high St 3 52" 14' X Matthews
Mombo combo St 4 76" 27' X Matthews
Light duty combo St 2 48" 10' 5" X American
Heavy duty, 2-riser St 2 50" 11' 3" X American
Heavy duty, 3-riser St 3 51" 14' 3" X American
Alum combo, 2-riser St/Al 2 48" 10' 3" X American
Alum combo, 3-riser St/Al 3 51" 13' 9" X American
Mombo combo St 4 5' 8" 23' 5" X American
Stands and Rigging 115
T-Bones and Turtle Stands
A T-bone is simply a metal T fitted with a junior receiver (Figure6.4). A Tbone
can be nailed or screwed into place (typically in green beds or onparallels). It
sits flat on the floor, providing a low position for larger lights.A turtle stand is
nothing more than three legs joined in the center to a juniorreceiver. Matthews’s C
+
stand has removable legs, which serve as a turtle stand. The risersection of the C
+
stand can be used as a stand extension. Matthews and othermanufacturers also make
wheeled turtle stands. Matthews calls theirs a runway stand.
Mombo Combo
A mombo combo is a very substantial, four-riser, steel stand with avery wide
base (no wheels), which allows a maximum height of more than 26ft.
Table 6.1 Stands (continued)
Name Type Risers
Minimum
Height
Maximum
Height
RM
Leg Brand
Standard 2 54" 11' 2" X Norms
Sky high 3 58" 13' X Norms
Sky high Al 3 61" 13' X Norms
Notes: RM leg stands for Rocky Mountain leg.
St/Al means the stand has steel legs and aluminum risers.
Figure 6.3 The 11/8 -in. junior pin fits into the receptacle on thestand. The T-handle should
engage the indented part of the pin. Some stands have a babypop-up, which allows the junior
stand to support either a baby or a junior fixture. An angleddrop-down offset allows a light or
reflector to hang lower than the lowest height of the stand. The45
° angle holds the light away
from the stand. In the absence of a baby pop-up, a junior standadapter can be used.
116 SET LIGHTING TECHNICIAN’S HANDBOOK
Offsets, Side Arms, Extensions, and Right Angles
Offsets
Figure 6.5 shows various types of baby offsets that can be used tolocate the
head out from the stand. They are useful when some obstruction,such as furniture
or a set piece, prevents the stand from being placed under thelight. Note that an
Figure 6.4 Three ways to place a light near the ground. A T-bonecan be nailed or screwed
into place in green beds or on parallels.
Figure 6.5 Offsets, side arms, double headers, and triple headersare available in baby
and junior sizes (babies are shown here).
Stands and Rigging 117
offset or side arm puts the stand off its center of balance. Usesandbags on the legs
as counterweights.
Risers
Risers come in many sizes; typical sizes would be 6, 12, 18, and 24in. A riser
is a handy piece of hardware when a light mounted to a plate orclamp is not quite
high enough. A 36-in. junior stand extension essentially adds anadditional riser to
a stand. It can also be inserted into the receiver on the dolly orthe crane when a
light is to ride with the camera.
Using Stands
• See Chapter 2, Checklist 2.3, for check-out procedure forstands.
• Remember, “Righty tighty, lefty loosey.” Lock-off knobs(T-handles)
tighten when turned to the right (clockwise) and loosen when turnedto the
left.
• Extend the top riser first. If you extend the second riser first,you will raise
the first riser out of your reach and look like a bonehead.However, if the light
is heavy for the stand, you can add strength to the stand by notusing the first
riser or using only part of it.
• Bag any raised stand. A good rule of thumb is one sandbag perriser. If the
light is extended all the way up on a three-riser stand, you woulduse three
bags. Place the sandbags on the legs so that the weight rests onthe stand, not
on the floor.
• Get help when needed. As a rule, use two people to head up anylight 5k or
larger. Depending on the height of the stand and the awkwardness ofits
position, heading-up a 12k or Dino can require three or fourpeople. Don’t
hesitate to round up the other electricians and grips when you needthem. It
is poor judgment to underestimate your needs. A heavy light can getaway
from you and cause injury and damage. Moreover, handling largelights alone
tires you out before the day is over and, in a short time, islikely to lead to
back and knee problems. I know too many people in their middle andlate
thirties who have done permanent damage by abusing themselves whenthey
were younger. Lifting equipment is not a contest; the lighting crewworks as
a team.
Crank-up and Motorized Stands
Crank-up stands provide a mechanical advantage needed for raisingheavy
lights. Table 6.2 gives the weights and weight capacities ofcrank-up and motorized
stands. They have a chain-, cable-, or screw-driven telescopingextension system
with a crank and clutch, so that the crank does not reverse andspin out of control
under weight. Do not crank up a stand without some kind of weighton it, as this
can cause problems in the inner mechanisms.
The Cine-Vator, Molevator, and similar motorized stands power thetelescoping
mechanism with an electrical motor that is operated by a singleup/down toggle
118 SET LIGHTING TECHNICIAN’S HANDBOOK
switch (Figure 6.6). These stands can handle the heaviest lightsmade (up to 300 lb).
The motor is usually 115-V AC (at about 6 A) but can be 115-V DC,220-V AC,
or 220-V DC.
• When rolling a large light on a crank stand or motorized stand,push the stand
from the back with the swivel locks unlocked on the two rear tiresand the
front tire locked. Steer by pushing the back wheels left or right.This way you
are less likely to catch in a rut and tip over the wholestand.
• When the stand is in place, prevent the stand from rolling byswiveling each
wheel straight out from the stand and locking each swivel.Additionally,
wedges in the tires and cup blocks under the tires prevent themfrom turning
(grip department).
• Before raising the stand, make sure it is totally leveled withcup blocks,
wedges, and apple boxes, if necessary (grip department).
• Use your strong arm to turn the crank to raise and lower thelight. Never
release the clutch without having a good grip on the crank. Aproperly adjusted
crank should not spin when the clutch is released. However, theyoften do. If
the crank gets away from you, there is a good chance you will notbe able to
Table 6.2 Weight Capacities of Crank-up and Motorized Stands
Floor Ceiling Capacity Type
American
Roadrunner 220 4' 2" 11' 3" 220 lb (100 kg) Crank
Big Fresnel lamp stand (BFL) 4' 2" 12' 6" 300 lb (136 kg)Motor
Arri
Baby 2-section Supercrank 3' 2" (97 cm) 5' 5" (165 cm) 220 lbs (100kg) Crank
Short-base 3-section Supercrank 4' 8" (153 cm) 11' 3" (345 cm) 154lbs (70 kg) Crank
2-section Supercrank 4' 10" (147 cm) 7' 7" (232 cm) 198 lbs (90 kg)Crank
3-section Supercrank 5' 5" (165 cm) 11' 5" (348 cm) 176 lbs (80 kg)Crank
4-section Supercrank 5' 11" (182 cm) 15' 7" (477 cm) 154 lbs (70kg) Crank
5-section Supercrank 7' 9" (237 cm) 20' 4" (620 cm) 154 lb (70 kg)Crank
Matthews
Lite Lift 4' 1" 8' 6" 85 lb (38 kg) Crank
Crank-O-Vator 4' 11" 12' 150 lb (68 kg) Crank
Low Boy Crank-O-Vator 3' 2" 5' 5" 150 lb (68 kg) Crank
Super Crank 5' 9" 12' 6" 200 lb (90 kg) Crank
Cine-Vator 4' 6" 12' 300 lb (136 kg) Motor
Mole-Richardson
Folding Crank-up Litewate Stand 4' 5" 10' — Crank
Molevator 5' 1" 11' 1" 250 lb (113 kg) Motor
Stands and Rigging 119
get hold of it again before the lamp hits you in the head. There isalso a good
chance you’ll hurt yourself trying to grab hold of the spinningcrank. If you
lose control, let go of the clutch and get out of the way of thelight.
Grip Stands
For the most part, the grip stands are used for flying overheadsets and setting
flags, nets, diffusion frames, and so on. However, in specialsituations, they are
needed as light stands.
C-Stands
Q: How do you drive an electrician crazy?
A: Lock him in a small room with a C-stand.
The Century stand is a versatile, all-purpose, rigging gadget thatis the centerpiece
of the grip’s equipment. Its components are like the parts of anerector set, and setting
C-stands is a little-appreciated art form. Given enough time andenough C-stands, a
grip could build a scale model of the Eiffel Tower. When a C-standis used as a light
stand, however, it becomes the electrician’s responsibility(Figures 6.7 and 6.8).
Figure 6.6 A Cine-Vator stand. (Photo courtesy Matthews StudioEquipment, Burbank, CA.)
120 SET LIGHTING TECHNICIAN’S HANDBOOK
Figure 6.7 (A) C-stand supporting a light fixture. (B) Orient theknuckle so that gravity
tightens it (“righty tighty”). (C, D) The grip head accepts varioussizes: a 5/8 -in. hole for the
gobo arm or a baby pin; a 3/8 -, 1/2 -, or 1/4 -in. hole for netsand flags. (E) The light fixture
shown uses a bar clamp adaptor (used on furniture clamps) to attachto the gobo arm.
Stands and Rigging 121
Knowing the proper technique will save you much embarrassment;grips like
nothing better than to heckle an electrician who is making a messof a job with a
C-stand.
• Place the longest leg under the extended arm. This helpsstabilize the stand.
Always sandbag the legs when putting weight on an extended arm(Figure 6.7).
• Work with gravity, not against it. When you are standing behindthe stand
with the arm pointing away from you, the knuckles should be on yourright.
In this way, when weight is put on the arm, gravity pulls the griphead
clockwise, which tightens it. If the knuckle is on the left, theweight will
eventually loosen the knuckle, and the whole rig will collapse(very bad form).
• Avoid configurations in which the back end of the arm sticks out,especially
at eye level; it could hurt someone. There is almost always analternative
configuration that eliminates the hazard. If it’s unavoidable,place a tennis ball
or styrofoam cup on the end of the arm so people will see it.
• Place the sandbag on the top leg so that the weight is on the legand not resting
on the ground.
• Always place the C-stand on the “off-camera side” of thelight—the outside,
as viewed from the camera. This helps keep grip equipment out ofthe movie.
• When a lot of torque is placed in the gobo head, configure thestand so that
the flag rests on the T-handle (Figure 6.9). Do not rely on thestrength of the
grip head alone. I’ve strayed into the domain of gripology here,but what the
heck, I’m on a roll.
Figure 6.8 Some special uses for C-stands: (A) to place the lightin a low position; (B)
to arm the light out over the action (here, two gobo arms a coupledtogether); (C) a bounce
card rig like this uses a single stand to support the light, bouncecard, and a net.
122 SET LIGHTING TECHNICIAN’S HANDBOOK
• Take wind into account. When setting 4-by frames or flags in awind, use a
larger stand with a wide base, such as a combo stand. A C-standdoes not
handle big flags or frames well in any kind of wind.
Medium, Hi, and Hi-Hi Rollers
A medium roller stand is slightly taller than a junior combo, about14 ft
maximum, and has wheels, which makes it easy to move around. Thewheels have
brakes that should be locked once the stand is placed. In additionto a junior receiver,
roller stands typically provide a 4-in. grip head for mountingoverhead frames, large
flags, and other grip gear. A hi-hi roller is especially usefulwhen height is required;
it has a maximum height of 20 ft.
Booms
Boom poles allow a fixture to be cantilevered over or behind theactors in
places where it could not be mounted by other means. Booms vary insize and
strength. The small ones mount on a baby stand and provide about a4-ft arm with
almost as much counterweight length. The larger ones mount on ajunior stand, have
Figure 6.9 Large cutters can be supported by the knuckle on theC-stand.
Stands and Rigging 123
more length and more counterweight, and provide either a junior ora baby mount
for the light. Sandbags can be added for additionalcounterweight.
Stand Maintenance
Modern stands are made of stainless steel and aluminum. Stainlesssteel stands
are extremely weather resistant. A well-made stand will not rust orcorrode. When
stands get muddy, they should be cleaned so that dirt does not getinside, between
the risers. Wipe each riser down with a rag or towel. If a riserstarts to bind, lubricate
it with silicone spray.
Occasionally the Allen screws that secure the bonnet castings andthe riser
castings to the tube parts of a stand get loose and the castingscome off. It is a simple
matter to push the castings back into place and tighten down theAllen screws. Be
sure to keep the castings tight. If the casting comes off while youare raising a light,
the riser will separate from the stand and you’ll wind up balancingthe light on a
pole like an acrobat with tea cups.
Rigging Hardware
Baby and Junior Nail-on Plates
A nail-on plate, also called a wall plate or pigeon plate (Figure6.10), mounts
to a surface with screws. Use a cordless electric drill with aPhillips bit and wood
or drywall screws. The plate can be mounted to a horizontalsurface, a wall, or a
Figure 6.10 Plates and hangers for set walls.
124 SET LIGHTING TECHNICIAN’S HANDBOOK
ceiling, but be sure you are screwing into something solid. If youare screwing into
a set wall (usually 1/4 -in. plywood), place a piece of cribbing onthe other side of
the wall to give the screws something to hold to.
The grips usually prepare several apple boxes with nail-on plates.When
mounted on an apple box, a nail-on plate provides a stable lightingposition that is
handy for setting a light on the floor or on a counter top.
Set Wall Mounts
Figure 6.10 shows a variety of set wall mounts.
Set Wall Bracket
A set wall bracket is a right-angle plate that mounts to anyright-angle corner,
such as the top of a flat.
Crowder Hanger
A crowder hanger fits over the top of a door or on a 2 × 4-in.beam. It can
be used with a baby adapter that provides two mounting positions,one above and
one below the hanger.
Edge Plate Bracket
An edge plate bracket is similar to a crowder hanger. It is used tomount lights
to the side edge of a green bed.
Wall Sled
A wall sled is suspended on rope from the top of a set wall. Theweight of
the light holds the sled in position against the wall withoutscrews or tape. Wall
sleds are made with either a junior or a baby mount.
Trombone
Like the crowder hanger, a trombone also fits over the top of theset, but it is
adjustable to any width of wall. It provides an adjustabledrop-down position for
the light. Use a rubber ball on the telescoping arm to prevent itfrom scraping the
wall. A trombone can have either a junior or a baby mount.
Clamps
C-Clamp
C-clamps (Figure 6.11) come in various sizes: 4, 6, 8, and 12 in.Each one
has two baby pins or a 11/8 -in. junior receiver welded to it. Thefeet are either round
and flat or squared off. The squared metal clamps are designed formounting to pipes.
With any of the clamps shown, to prevent puncturing or marring thebeam
and to increase the surface area of the clamp, insert two pieces of1 × 3 in. cribbing
between the clamp and the surface. Wrap the cribbing in duvetynwhen it is important
not to scratch the finish.
A common problem when mounting lights to a C-clamp on top of theset wall
is that the light cannot be tilted down far enough. Use the angledpin on a C-clamp
to get around this problem.
Stands and Rigging 125
Furniture Clamp and Bar Clamp
Furniture clamps and bar clamps are normally used by woodworkers toclamp
workpieces together during glue-up. Furniture clamps come invarious sizes (6, 12,
18, 24, and 36 in.); standard bar clamps are 48 in. (but can be anylength), all of
which are adjustable. Furniture clamps are typically used toundersling lights from
ceiling beams or square pillars that are too wide for a C-clamp. Aswith C-clamps,
use cribbing to increase the surface area of the clamp and toprotect the surface to
which you attach the clamp.
Gaffer Grip
A gaffer, or gator, grip is a spring clamp with rubber teeth. It isused to mount
smaller lights to doors, pipes, and furniture.
Mafer
A mafer (pronounced may fer) is a very strong, versatile mount, afavorite
clamp-type mount. A cammed screw mechanism closes and opens therubber-lined
jaws. It can attach to any round surface from 5/8 –2 in. indiameter and any flat surface
from 1/16 –1 in. thick. The baby pin snaps into place with aspring-loaded lock.
Figure 6.11 Clamps.
126 SET LIGHTING TECHNICIAN’S HANDBOOK
The removable pin can be exchanged for accessories, such as a flexarm, a doubleheader
offset arm, or a right-angle baby pin.
Vice Grip
The adjustable width of a vice grip provides a strong grip. As withany vice
grip, the clamp is released by pressing the unlocking handle.
Chain Vice Grips and “Candlesticks”
Figure 6.12 shows a correctly threaded chain vice grip. A chainvice grip
provides a very solid mount to any pipe up to 6 in. in diameter. Itis used to mount
a light to a standing pipe or pillar. Using a chain vice grip ispreferable to using a
clamp in this application because a clamp can crush a pipe, while achain vice grip
applies force more evenly around the diameter of the pipe. Chainvice grips are
often used to secure a “candlestick” to a standing post. Acandlestick is nothing more
than a heavy metal tube, one end of which is sized to receive ajunior pin. It is like
a junior riser but is stronger because it does not have a castaluminum receiver.
(When heavy lights are rigged to an aerial lift, for example, agreat deal of sideways
force may be exerted on the receiver when the aerial lift stops andstarts. A normal
Figure 6.12 Face the tray up, toward you. Wrap the chain around thepost and into the
tray. Engage the chain’s pins into hooks and squeeze the vicehandles until they snap closed.
To loosen or tighten the tension, turn the knurled knob beforeclosing. Wrap tape around the
handles to ensure the vice does not open if it gets accidentallybumped. To release, remove
the tape and pull the release lever.
Stands and Rigging 127
junior receiver casting can crack open under such stresses.) Tomake sure that the
vice grip does not open, always wrap tape around the handle afterthe chain vice
grip is in place.
Be very careful if you are considering mounting small lights toplumbing pipe
on location. Although it may look sturdy, old cast iron pipes canbe paper thin,
corroded on the inside after years of use. In any case, do not usea pipe clamp or
C-clamp, use a chain vice grip, as you stand a better chance of notrupturing the
pipe. Never mount lights to fire sprinkler system pipes. It isagainst fire codes and
a bad idea. If you rupture the pipe, it can flood the set.
Grids and Green Beds
Pipe Clamp
Pipe clamps (Figure 6.13) are used when hanging lights from anoverhead
pipe or grid. Pipe clamps come with a safety pin attached to theclamp with a safety
chain. The cotter pin prevents the receiver from slipping off thepin. Always use
the safety pins when hanging lights.
Telescoping Stirrup Hanger
To get a light lower than the height of the grid, use a telescopinghanger to
lower it to the desired height. Hangers have a stirrup to which youattach a pipe
clamp. They are also made with a baby pin or junior receiverinstead of a stirrup.
Greens and Bazookas
In most studio sound stages, wooden catwalks called greens or decksare
suspended above the set to provide lighting positions. Along theedge of the greens,
at 18-in. intervals, are holes onto which a junior pin fits. Alight may be inserted
directly into this receiver or a bazooka can be inserted into thehole. A bazooka is
like a one-riser stand with no legs. An L-shaped bracket fits overthe catwalk’s hand
rail to support it.
Figure 6.13 Pipe clamps.
128 SET LIGHTING TECHNICIAN’S HANDBOOK
Location Rigging Hardware
Wall Spreader and Tube Stretcher
Wall spreaders (Figure 6.14) support lights by exerting pressureagainst two
opposite walls or the floor and ceiling. A 2 × 4-in. or 2 × 6-in.piece of lumber
creates the span. The hardware mounts to either end of the lumberand uses a threaded
post to apply pressure against the walls. Lumber must be cut to fitthe particular
span needed.
A wall spreader can create a secure overhead beam of up to about 16ft from
which lighting fixtures can be hung. With a long span, be sure thehardware is
aligned with wall studs and screw the wall spreaders to the wall. Atube stretcher
essentially adapts a wall spreader for use with speed-rail pipeinstead of lumber.
Matth Pole
A matth pole, or pole cat, is a smaller, lighter-duty version of awall spreader,
especially useful in doorways or narrow halls or used verticallybetween floor and
ceiling. A Matth pole can support lightweight fixtures and gripequipment.
Suction Grip
Suction grips of 4 or 6 in. can be used to affix small lightingunits to nonporous
surfaces, such as a window or car hood. These grips generally use acam to create
the suction; they are not as strong as the larger, pump-type grips.Suction grips come
with baby pins only and should be limited to use with smallerlights.
Figure 6.14 Location (and stage) rigging equipment.
Stands and Rigging 129
Scissor Clip
A scissor clip is used to mount a light to the metal supports of adropped
ceiling. The scissor closes over the metal strips that support theceiling tile. It is
tightened in place by turning the 5/8 -in. pin. Cables can bedressed above the ceiling
or clipped to the metal strips with small grip clips.
Putty Knife
A putty knife can be wedged in a windowsill or door frame. Itprovides a baby
pin for a small light fixture.
Trapeze
A trapeze is used to dead hang a light of any size from a rope. Itprovides a
junior receiver. Eyelets at each end of the trapeze are providedfor guy wires, which
aim the light and hold it in place once in position.
