NOVA: What are the challenges of using an IMAX camera underwater?
Howard Hall: Just about every facet of production is more complicated. Whether
it's video or 16 mm, a television camera in an underwater housing might weigh
45 pounds, and it will hold anywhere from 12 to 60 minutes of film or
videotape. The IMAX system weighs 250 pounds once it's in the underwater
housing, and it only runs for three minutes. Which means you have to be
extremely careful about when you push the button to roll film. You have a
limited selection of lenses you can use in IMAX; we don't use zoom lenses, for
instance. You need a larger crew. And you need different equipment and lots of
(with IMAX camera) and Bob Cranston on the seafloor.
NOVA: Now, you've modified some equipment and even built entirely new equipment
to make this happen, right?
Howard Hall: To make a good natural history IMAX film, I needed a much broader
selection of lenses and capabilities than were available with the equipment
IMAX already had. So we modified an IMAX camera and built an underwater housing
to protect it. The housing alone took us a couple of years to construct. We
also built special lighting systems, light meters, and a tripod, all for use
underwater. And we started using underwater communications so that we could
talk to the surface and talk to each other while diving.
Hall using bubbleless rebreather.
NOVA: You've also been using "rebreather" scuba gear. Can you describe what
that is and why you use it?
Howard Hall: In giant format, everything takes longer—setting up a shot,
getting the camera to a position to mount it, mounting it, and getting it
steady so that currents and surges aren't moving it around. Standard scuba
equipment gives you limited time. At a depth of 100 feet, which we're working
at quite a bit, your air only lasts about 40 minutes. That's just not long
enough. To do the IMAX film, we've almost exclusively used rebreathers. These
are fully closed-circuit devices that recirculate all the gas you're breathing,
taking out the carbon dioxide and replenishing the gas with oxygen. It creates
no bubbles, it makes no sound. With the unit we're using, which is a Navy Mark
15 system, we can stay down as long as 12 hours on a single dive.
Shooting a green turtle at Cocos.
NOVA: How do fish react to your 250-pound camera?
Howard Hall: Unlike the rebreathers, the camera makes a helluva lot of noise,
and most of the animals take off like bats. That's especially true of
hammerheads. Plus, the camera takes almost five seconds to rev up to speed and
begin capturing an image. In order to get a good shot , I have to anticipate
the animals coming way ahead of time. So I'll see, for example, a school of
sharks maybe 150 feet away coming in my direction. I'll turn the camera on,
hoping to get them coming into the scene. But typically by the time the camera
is running to speed, the noise has already frightened the sharks away. We are
getting good shots of hammerheads, it's just taking a lot longer than I
Time-lapse filming of starfish.
NOVA: How much filming do you do to get the single two-minute sequence of a
particular animal that will end up in the finished film?
Howard Hall: We're shooting about a 20-to-1 ratio. That's 20 feet of film for
every foot that will actually end up in the film. We'll shoot almost 300 rolls
of film during this production, which means that we have to make at least 300
dives. Since each dive typically lasts at least an hour and a half, to get
those 300 rolls of film we'll have to spend 450 hours underwater.