by Steven T. Smith
Lighting for Video- Part IV
This is the
chapter where lighting for video takes an exotic and expensive turn,
for here we visit the Hydragyrum Medium arc Iodides– the fabulous
HMI's. Watt for watt, these fixtures are two to four times brighter
than their tungsten equivalents. In the past quarter century their
use has revolutionized motion picture photography.
Though the principle
behind the HMI has been known for decades, it wasn't until the late
1960s that lamp developers turned their attention to applications
for film and video. At the request of German television (seeking,
ironically, a less expensive alternative to incandescent lights),
the electrical giant Osram began work on HMI bulbs.
my first HMI on a Hollywood soundstage in 1974, two years after
its introduction. It was an impressive luminaire, but those early
models had a number of drawbacks–not the least of which for a cinematographer
was the "flicker problem."
HMI lights are
ballasted sources (as are common fluorescents), which means they
pulse on and off a fixed number of times per second– that is, they
flicker. If you're shooting film at 24 frames per second, or video
at 30 frames (60 fields, corresponding to the frequency rate of
the electrical source, 60Hz) you won't see the flicker. But if you
take your 30fps NTSC camcorder overseas, where the power is 50Hz,
there will be a pronounced flicker (which, incidentally, you can
make disappear by setting the camera's shutter to 1/100th second).
problem with early HMI's mainly affected cinematographers who wanted
to shoot at non-standard frame rates or shutter settings. The introduction,
about a decade ago, of electronic "flicker-free" ballasts means
that cameramen can shoot at most any speed they want without worry.
This issue has little bearing upon the video photographer, except
that the new ballasts weigh a fraction of the old magnetic versions,
and hence, for the first time, location use of HMI's became feasible.
The main drawback
of HMI fixtures is their cost. Whereas a 300w Arri Fresnel costs
less than $300, the 200w Arri HMI costs over $2000– costs, in fact,
about as much as a Canon GL1. With prices like these, why use HMI
in the first place?
light they put out looks gorgeous.
First of all,
HMI's are daylight balanced– their output is 5600 Kelvin.
most important, the light from HMI's seems to have the ability to
"wrap around" objects and subjects (at least that's how many DP's
describe it); seems to fill space with bright, happy light. I know
that sounds pretty corny, but after you've worked with incandescent
light– that warm 3200 Kelvin stuff– the cool, bright illumination
of an HMI seems revelatory. Okay. You got to see it and work with
it to fully get it. So, let's work with it.
When to use
They are especially
well-suited for exterior work. Shooting on a shady patio with a
bright background and no direct sun off which to bounce a reflector?
A 400w or 575w HMI fixture will balance the subject with the background,
while adding some definition to the face.
a blown-out sky and want to see your subject's face? You'll need
a big guy, at least a 1200w, and maybe a 2500 or 4k. Be aware that
when you go above 1200w you'll have to arrange for some appropriate
power– a standard household 15A or 20A circuit is going to get blown
sky high (and perhaps the house along with it) so do be very careful.
BTW. When shooting
exteriors here are a couple of tricks you can use to make any situation
look better, even if you don't have HMI's on hand:
To smooth out
direct, overhead sunlight (i.e., that ugly kind that makes your
subject's eyes disappear into black sockets) you can insert some
diffusion between the great orb and your subject. In the industry
these are called "silks." A piece of Tough Frost, or even a white
sheet will do the trick. The folks at Chimera make a lightweight
frame and fabric system perfect for this purpose. It can be handheld
or mounted to a light stand. In a pinch, I once even used an umbrella.
We were shooting an interview at an elephant farm in southern India.
The subject looked awful under the merciless equatorial sun, so
I begged a bystander to hold his black brolly over my chap's head.
Instant diffuse light. Yes, I lost a couple of stops on his face,
however the background was not so bright that it overpowered the
But what if
that BG had been too bright? An easy trick for such situations is
to run a couple of yards of back scrim right across the background.
Yes, it's in the shot, but if you smooth out any wrinkles and keep
it back far enough, the camera won't know its there. I usually carry
a small bolt of double scrim (equivalent to a full f-stop) for this
purpose. You can buy this material from Matthews, or you might find
a suitable substitute at a fabric shop.
What about using
If you're shooting
in a room full of windows, HMI's are a great way to go. Remember,
that a 400w fixture is going to put out more illumination than a
1000w tungsten light. I can often get away with using a single HMI
to do an interview in such a setting– employing a bounce card for
fill. The biggest HMI job I ever had was lighting a high-profile
two-camera interview with Woody Allen for "60 Minutes." The location
was his penthouse suite overlooking New York's Central Park. And
of course, there were huge windows on three sides. We had to consider
not only lighting Woody and correspondent Steve Kroft perfectly,
but also take into account the sun, which would move from one side
of the flat to the other, during the course of a long interview.
We ended up using three 1200w Arripar fixtures bounced into 4x8
sheets of foamcore (which also helped to block light coming in from
the windows). Fill was provided by a couple of heavily-diffused
200w Joker lights. Then, to light the background, I used a single
575w fresnel. In the end, it all looked great. It was one of those
jobs that could not have been done in that setting and at that time
of day with standard tungsten lighting. Hooray for HMI's.
Now, I know
you're not going to run out and buy these things. A small set of
small lights can set you back $10,000. But when you really need
the punch and wrap-around light of an HMI you can rent them. A 200w
Joker might rent for $35-50 a day; a 1200w PAR for $75-125. Renting
will not bust your budget, and will help give your production a
very polished look (it will also make shooting possible in otherwise
For the next
installment I'd like to hear from you– your questions or comments–
on any and all things lighting. I'll do my best to provide illuminating