Introduction
A few decades ago the only way to capture fast moving birds in flight was by using flash. It was an exacting science that was mastered by only a handful of exponents in this country starting with the likes of Eric Hosking and mastered and evolved by Stephen Dalton. With the advent of digital cameras and the superb technology that they incorporate superb flight images can be created now of all manner of taxa and slowly the domain of the high speed flash decreases. One area that will remain the domain of the flash photographer for some time is that of the nocturnal world so flight images of bats and owls other than infra red images will still be taken by the methods outlined below for some time.
There tends to be little flexibility with the requirements for high speed flash photography. Each area has its critical requirements, and the photographer ignores them at his/her peril.
Flash units
I only have experience using custom built flash guns but there’s no reason why off-the-shelf flashes can’t be used. For freezing fast wing movement of bats and birds the flash guns that allow only you to use a fraction of the power to limit the duration of flash will be required.
My first flash units were custom built many years ago by Professor Greg Parker and though I’ve had other commercial guns, these were without doubt the best. Unfortunately I treated them like I treat all my gear and sadly only two now work so I have to use the modern but inferior American units. On the other hand, the new guns are a lot safer to use as they lack the drinks can-sized capacitor that discharges 2000 volts in 40,000th of a second. One of my older flashguns had been hung up in my shed and unbeknownst to me the roof had developed a leak that unfortunately had trickled water into this unit over a period of weeks. When I powered the unit up it whined to high pitch as usual and then just exploded with an enormous bang.
My new flash guns have the ability to fire a flash at around 28,000th of a second. They are powerful enough to illuminate a subject 2 metres away enabling an aperture of f16 (when using 100 iso film or equivalent digital sensitivity). I have four flashes and each is powered by its own 12 volt battery. Powered continuously and fired every few minutes, I would expect the battery to last through the night. The guns are waterproof and about the size of a box file.
Shutter
The shutter speed may not seem important as it’s 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, and for this reason a compur (leaf) shutter is best as it can sync up to 500th sec on cameras like Hasselblad EL /ELM. What is perhaps the most 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 the subject triggers the camera. Once again the fastest response times are from the leaf shutter cameras but a DSLR with the mirror locked up can be used. Canon 1D MK4 and 1DX MK2 are now my main cameras.
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, burglar alarm beams, pir type sensors etc. Saying that, I prefer a custom built infra red beam set-up that fits a number of cameras. A cheap digital remote 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 disturbance of a wild subject or simply used as a delay so the guns can recharge, though the guns can recharge in around a second now so the latter use is less likely.
Iso
As mentioned previously, ambient light can be a problem as it can cause a secondary image if too much light is allowed to fall upon the subject, so the slower the film or chip sensitivity option the better. I only ever used Fuji velvia (50 iso) and Fuji provia (100 iso) and now on digital I limit it to 100 iso but will use 50 iso in bright sun. Reciprocity failure experienced with film is obviously not a problem with the non-organic digital sensor.
Aperture
I have to work with as small an aperture as possible, as ambient light has to be omitted and maximum depth of field has to be achieved. A subject in action such as a bird in flight may have the same biomass as when it’s perched but the depth of field it requires is much more demanding if its body is twisted and wings spread out. An aperture of at least f16 should be aimed for and a standard lens through to maybe 200mm on a 35mm DSLR should be adequate. Remember, it’s not how close you yourself can get to the subject but how close your equipment is, and believe you me, a camera and flashes is more more acceptable that the large threatening form of a human. The ability to predict the optimal~ focus point is of great value though not easy.
Digital
I thought digital cameras may cause problems for my flash gear setup as the shutter would be limited to its flash sync speed which would normally be between 60th and 250th (vertical plane) which had always been 500sec with the Hasselblad because of the compur shutter and the propagation delay would be too long, but my fears were unfounded – I use the shutter at about 320th of a second and with mirror lockup the propagation delay is manageable. One problem I had to get around was that of the power saving feature on my canon; every time the shutter was up for around 38 seconds, the mirror would drop back down. The only way I could see around this was to have a remote release that was timed to fire the camera every 39 seconds so every time the mirror dropped down it would flip back up again; this did not fire the camera though, only the mirror. The benefits of digital have far outweighed that of film cameras for the HSF work; to check lighting, fogging, focus or even to know when you’ve got that one shot that you were after.
How it works
The beam should be set across the known flight path of the subject and the flash gear should be set up to illuminate that space adequately. The lens should be focused on an area just in front of the beam to allow for the small delay that it will take the electronics and mechanics of your camera to fully open the shutter, close the aperture, and fire the flashes. This will come with experience but allow for the different speed of various animals; a badger bumbling through an infra red beam may travel a fraction of an inch by the time the camera fires whereas a swallow could fly 18 inches in the same time. Remember that a subject flying across a focal plane will be easier to retain focus on than a subject flying towards you.
Equipment
eBay tend to have a range of cheap electronic triggers that can be used for – but not necessarily built for – photography. Noise triggers can work where shots involve hitting a golf ball, dropping an egg, popping a balloon, firing a gun etc, whereas an infra red beam emitter and receiver kit can be used movement.
Caution
Please be aware that certain animals are protected and licences may be required for schedule 1 and schedule 5 animals. Though I have a licence to disturb bats for the purpose of science and education, disturbance licences for the inside a bat roost are rarely issued, but bats in other areas such as cave entrances away from a roost, or feeding areas, navigation routes, tunnels etc can be undertaken without a licence. Incidental images can also be taken when other licensed activities such as mist netting is taking place.