The BurningCam Aerial Photography Technical FAQ
The BurningCam Aerial Photography Technical FAQ
Okay, so this isn’t really an FAQ since I haven’t written it up in the form of questions. And it only covers the year 2000 balloon rig and not the 2001 kite rig. But anyway, here’s a photo of the finished rig:
Here are the various components and what they do:
The camera itself is now housed in a cheap plastic storage box of some kind that I bought for 25 cents at Archie McPhee’s in Seattle. Not very tough or anything, but certainly lightweight. The whole thing is held in place with hook and loop velcro fasteners so I can easily switch between the colour and black and white cameras.
The XCam2 (and its virtually identical but AC remote-switchable sibling, the ScanCam) is very cheap. In both senses of the term. One serious drawback of the system is that the camera itself isn’t very good. It’s a cheap colour CMOS camera that has really awful low-light sensitivity, partly because of its crappy slow (high equivalent f-stop) lens. So I replaced one of the cameras with a CCD black and white camera that offers far higher quality and works better in low-light conditions. This was pretty important since my original plan was to use the BurningCam to videotape the night of the Burn. (this didn’t happen, of course)
Fortunately I discovered that replacing the XCam2’s lens with a higher-quality lens meant more light comes in, which meant astoundingly better low-light sensitivity. Unfortunately it doesn’t help the low quality of the image at all. The monochrome camera, by contrast, is remarkably high quality. It’s a CCD-based camera from Supercircuits, and can detect infrared light for incredible low-light sensitivity. It’ll show a beautiful black and white image in a room lit by a candle. Its lenses are interchangeable with the XCam2’s. I put a massively wide-angle lens on it for fun, then put the lens that shipped with it onto the colour camera.
Since the XCam2 camera uses plain NTSC North American video I was able to connect the replacement camera directly to the X-10 transmitter without any problems. However, the SuperCircuits camera doesn’t have an onboard microphone so I lost audio capabilities. Since the only noise you’ll really hear up in the sky is the roar of wind I wasn’t particularly concerned about this, however.
I chose this particular camera because a) it’s tiny, lightweight and just adorable, b) it uses 35mm film and not lower-quality APS film, c) it has a reasonably high-quality fixed focal-length wide-angle 28mm Fujinon lens, d) it has a motor winding mechanism so can be triggered remotely and then advance to the next frame and e) because it’s a discontinued item and Lens and Shutter Broadway in Vancouver sold it to me half price.
If the Fuji hadn’t been so cheap I would’ve gone for a Yashica T4 Super, (called the T5 outside North America) with its well-respected Carl Zeiss 35mm lens. This is the type of camera generally favoured by KAPers. (people into kite aerial photography - doing what I’m doing only suspending their cameras from kites and not helium balloons)
I disabled the flash and manually set the focus to infinity before sending up the balloon. One problem with this camera is that it’s got a 5-minute inactivity timeout. If you don’t press the shutter button (full or half way) for 5 minutes, the camera turns off. And the only way to turn it back on again is to close the lens cover, then reopen it. Handy feature for not draining your batteries in a bag. Not so handy for balloon cameras. My high-tech solution to the problem was to take a simple clockwork timer with me, so I’d know if I hadn’t taken a photo for the past 4 or so minutes.
The loop of fishing line beneath the camera is just a safety line to tie a few things together in case a bolt fell out or something.
I deliberately didn’t use the type of transmitter/receiver used on model aircraft. This is because I figured any interference from my stationary balloon rig would simply interfere with ground-based vehicles, which is less dangerous than interfering with an aerial model plane that might crash into something or someone. The legal situation is also a bit murky. By law airborne applications are required to operate on different frequencies from groundbased ones. But the regulations don’t exactly specify what a tethered helium balloon should use. Again, I feel it’s safer to use ground-based frequencies here.
Unfortunately, AM band receivers are more vulnerable to noise than FM, but it seemed to work fine most of the time.
Originally I was going to use an X-10 battery pack, modified for the rig. It’s basically a hugely overpriced plastic holder for 4 AA cells with a simple voltage doubler circuit board. Unfortunately my XCam battery pack died in a small puff of smoke the day before I left for some mysterious reason, and the replacement wasn’t due in until I was on the playa. So I opted for the lithium battery approach instead. Less stuff to go wrong. I didn’t power the radio receiver off one of the two lithium batteries, though it would’ve lightened the load, so that I wouldn’t cut too much into my run time.
The ultimate in low-weight solutions would have been to use the tiny 12 volt alkaline batteries they use in smoke detectors - they’re about half the size of a AAA cell. The run time would likely be massively short, of course.
The transmitter uses 2.4 GHz technology (the same unlicensed frequency band used by high-end cordless phones, Apple’s AirPort wireless LAN and microwave ovens) to broadcast a standard NTSC video signal, line of sight, to a small receiver up to 35 or so metres away.
I had about 50 metres of fishing line, but the balloons never got higher than around 5 metres anyway. (US FAA (civil aviation) regulations for tethered balloons kick in at 150 feet, so I was fine there)
I purchased the helium and rented the tanks from an industrial gas supplier in Seattle, since I didn’t want to attempt to ship large suspicious-looking gas tanks across the Canada-US border. This unfortunately held up my trip somewhat, because the gas company isn’t open on weekends.
I picked up the gas on Monday, and arrived on the playa late Tuesday night.
I’d tried to calculate the amount of helium required to lift my rig before
I left, using lift tables that I found online. Unfortunately the lifting
ability of helium can vary dramatically due to environmental conditions
- particularly altitude and ambient air temperature. I calculated I’d need
two or three balloons. I needed five. Luckily I’d brought nine balloons
with me, just to cover my ass in case of punctures, miscalculations, etc.
I also brought about three times more helium than I needed. Annoyingly,
the gas supplier wouldn’t refund me for the tank of helium that I didn’t
use, apparently in case I’d hooked up something else to the tank and contaminated
the gas. So I lost a bit of money on that. Ah well. Better that than to
go through all the rig-building craziness, only to arrive on the playa to
find that I didn’t have enough helium.
I did get to play Donald Duck with the helium, however, which was entertaining for a good two or three minutes. (safety note: inhaling helium in order to make your voice sound funny is not inherently dangerous because helium is an inert gas, but remember that 1) you want to breathe in the helium from a balloon, because wrapping your lips around a balloon filler nozzle on a high-pressure helium tank will rupture the alveoli in your lungs and kill you and 2) even if you inhale the helium safely from a balloon you might pass out because the helium gas will displace oxygen in your lungs and your bloodstream for a bit. So if you’re standing up you might pass out, fall down and injure yourself.)
