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The BurningCam Aerial Photography Technical FAQ




What does the year 2000 balloon camera rig look like?

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:

  1. Frame
    The frame for the whole thing is made of 1/8 inch clear acrylic plastic sheet, (plexiglas) custom-cut and shaped. It seemed like a good idea at the time to use plastic, as I thought it’d be lighter than metal, but it was a mistake. The plastic isn’t rigid enough - it tends to bend a little and send the frame out of alignment, even with the styrene plastic reinforcement beams that I installed. At one point the lower frame fell out when the rig was bouncing around violently in the wind. Ah well. Live and learn. (luckily I’d installed a fishing line safety cord to the lower frame in a fit of paranoia, so nothing fell off) The frame is attached to the balloon harness (a large metal split ring) by a bunch of small metal split rings, through which fishing line is run. I used 40 lb test, which I figured should be plenty overkill. It seemed to hold up just fine.

  2. Swivel section of the frame
    The lower portion of the frame swivels on this nylon bolt. The servomotor on the right-hand side (6) is used to rotate this lower section.

  3. Video camera
    This is one of the video cameras; originally an XCam2 manufactured by X-10, the firm famous for its horrendously tacky and thoroughly obnoxious popup online advertising. I took the thing out of its original housing so I could mount the camera independently of the transmitter, (I didn’t want the transmitter and antenna on the rotating section, because that would have meant the highly directional antenna would move as well) and so I could use lower-weight enclosures.

    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.

  4. Still film camera
    The still film camera is a Fujifilm Mini Cardia Tiara II camera. Yes. Tiara. I feel like Miss America when I’m using it.

    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.

  5. Second video camera mounting location
    There’s room on the rig to carry two cameras and transmitters at the same time, and this is the second velcro mounting patch. Unfortunately it turned out that having two transmitters in such close proximity can result in interference, even if they’re on different channels. I don’t know if the problem will go away if their power supplies are electrically independent - need to test some more.

  6. Swivel servomotor
    I used this standard servomotor on a direct drive to rotate the lower frame, so the cameras can point either straight down or nearly level with the horizon. I say nearly level because the servomotor doesn’t have a 90 degree range - more like 80 degrees or so. I could have opened up the motor and modified it, but I couldn’t be bothered. In case the weight of the lower frame strips the nylon gears in the servo I brought a backup that could be installed in moments if necessary. Metal-geared servos exist, but cost more.

  7. Radio receiver
    The radio receiver for the two servomotors. Just a cheap two-channel AM-band 75 MHz Futaba receiver designed for remote-control cars.

    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.

  8. Servomotor batteries
    The radio receiver and servomotors are powered by a 2CR5 lithium battery that puts out 6 volts. I used the 2CR5 because it’s the same type of battery used by my Canon Elan camera, and it seemed convenient to have a handful of interchangeable backup 2CR5s on hand. Lithium cells are a lot lighter than 4 AA alkalines - much higher power density. The drawback is that lithium photo batteries are pretty damn expensive.

  9. Video batteries (not shown)
    The video transmitter is powered by two 2CR5s wired in series to put out 12 volts. These two batteries are not shown in this photo, but sat in the middle of the rig at the top. They were held in place by double-sided foam tape, so I could move them to balance the weight of the rig.

    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.

  10. Shutter release servomotor
    The shutter release is a standard servomotor from Futaba. It’s mounted to a custom-made acrylic plastic holder with nylon bolts, and simply presses down the camera’s shutter release button by lever action. Primitive, but it usually worked. A more sophisticated approach would have been to open up the camera and attach a wire to the shutter release button itself, but I didn’t feel like risking opening up the tiny little camera and screwing it up. A mechanical solution seemed more straightforward, albeit less reliable and heavier. I could have used a micro servo motor to reduce weight, but the standard one was cheaper. It also means I could bring a single backup motor with me to the site, rather than two. I had a few problems with the shutter release at one point, but nothing a little duct tape couldn’t fix.

  11. Video transmitter
    This is the transmitter circuit board, now housed inside a semi-transparent plastic case originally meant for storing DAT tapes. The antenna is attached to the side of the case, and the whole thing is attached to the frame with velcro.

    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.

  12. Harness (not shown)
    The rig was attached to the balloon harness by a fishing line swivel. This is a little rotating metal doohickey that helps prevent fishing lines from getting tangled up. It worked quite well - the balloon lines kept rotating and getting tangled at the top, but it didn’t matter to the rig, because it was hanging from the swivel.

    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)

  13. Balloons
    I used five four-foot plain white latex balloons that I bought from Balloon Action on Denman Street in Vancouver. These apparently are called "paddle" balloons, though I have no idea why. Unlike weather balloons, which are designed to rise to a certain altitude and then burst, dropping their payload to the ground by parachute, these balloons appear to be made of a reasonably thick latex.

    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.)

  14. Winch
    From all this technical jiggerypokery to a pretty low-tech component. Here’s the balloon winch which I threw together an hour before leaving for the playa. Scrap wood, duct tape and an old poster tube.




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