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Summary There tends to be little flexibility with the requirements for high speed flash photography. Each area has its critical requirements, and if ignored, will result in an unusable image. Flash units My flash units were custom built many years ago and are still maintained by Professor Greg Parker. The guns have the ability to fire a flash at around 40,000 th of a second. They are powerful enough to illuminate a subject 2 metres away enabling an aperture of f16 (when using 100 iso film). They are powered by a 12 volt car battery, and at a guess, a fully charged battery would last me for a number of weeks. Powered continously and fired randomly, I would expect the battery to last between 8 and 12 hours. problems with the flash guns The guns are heavy, large (12 x 8 x 8), and fragile. The light emitted has a blue cast and therefore has to be corrected with an 81b warm up filter. I once thought that the high speed of the flash caused reciprocity failure but since using digital as well as conventional, I don't now consider this to be the case. Flashmeters in my experience give very strange readings with the flashguns so it is vital to know what distances are best and what effect a diffuser will have. The biggest problem has to be the danger. I have been assured by Professor Parker that the capacitor is capable of killing me if I'm unfortunate enough to connect with the 2,000 volt discharge it's capable of. A hefty warning was given regarding the obvious implications of working near water. Shutter The shutter speed may not seem important as its the flash that makes the exposure but when using this system in the field, it is crucial that ambient light is kept to a minimum and therefore the faster the shutter speed, the better. What is important, is the propagation delay. This is the time that it takes the shutter to fire after the signal for firing has been received, in effect, the delay after pressing the button. Trigger A number of triggers are available off the shelf, but a home made one can be just as effective. In the past I have used pressure plates, burgalr alarm beams, pir type sensors etc. Saying that, I prefer a custom built infra red beam set-up that fits both a medium format and a 35mm camera. It even primes the shutter for me on the 35mm. The designer has put a variable timer in so I can disable the system, for seconds or even hours, after it fires. This can be used to limit the diturbance of a wild subject or simply used as a delay so the guns can recharge. It is perfect for subjects like cavity nesting birds as the system will only trigger when the bird is entering the nest and not a few seconds later when leaving. Film As mentioned previously, ambient light can be a problem as it can cause a secondary image if too much is allowed to fall upon the subject, so the slower the film the better. I only ever use Fuji velvia (50 iso) and Fuji provia (100 iso). Aperture I have to work with as small an aperture as possible, as ambient light has to be omiited and maximum depth of field has to be achieved.
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