The photography of fast-moving objects is undeniably a rather technical undertaking and relies heavily on somewhat specialized electronics. It comes as a considerable surprise, therefore, to learn that high speed imaging is almost as old as photography itself.

In 1839 H.W.Fox Talbot recorded his first image with an exposure of several hours. Just four years later Daguerre introduced practical photography to an astonished public. In 1851, just 13 years after the very first photograph was taken, Fox Talbot used light from an electric spark to freeze movement with an exposure of ten millionths of a second.

The special problems that must be overcome to capture such subjects as birds & Insects in flight may be considered under several headings.

Lighting

The simplest way to freeze movement is to illuminate the action with a very short pulse of light from an electronic flash unit or strobe. Although it is possible to obtain flash durations as short as 1/50,000 second from some modern units, this reduction in duration is at the expense of light output. For our work we use homemade equipment that usually operates at 25 microseconds (millionths of a second) with a light output of 180 watt seconds. Although we have the ability to produce flashes of 5 microseconds or less, these have little application in photographing animal movement.

It is usually desirable to light a scene with more than one source, but special care must be taken to avoid multiple highlights in the subject's eye if the image is to be convincing. Exposures can be measured accurately even at very short durations using Minolta meters. However, it is necessary to use color correction filters as high-speed strobes produce a rather blue light.

Background

If a very brief artificial light source must be used on the main subject, it follows that any visible background must be similarly lit. Because the background area is so much greater than the subject, the inverse square law usually necessitates using artificial backgrounds with separate lighting, although digital techniques can provide an alternative solution to the problems of background illumination. Nocturnal subjects such as owls present no such difficulties.

Camera

If the action to be photographed can occur in darkness, then the camera plays a relatively unimportant role. In the absence of ambient light the shutter can be opened prior to the event and closed at leisure afterwards. This means, of course, that shutter speed plays no role.

However, many wildlife events such as birds or butterflies in flight can only take place in sunlight. In these situations it is of paramount importance to select an appropriate camera. What is involved in such a selection?

All cameras take time for the shutter to open fully, a delay that is increased further by the time taken for the mirror in reflex cameras to move out of the light path. Modern 35mm cameras take about one tenth of a second to respond, while large and medium format cameras require considerably longer. In the world of stop-motion photography such delays are wholly unacceptable because the subject will have long since left the field of view by the time the scene is finally recorded.

We use Rolleiflex 6000 series medium format cameras because it is possible for us to access the inner electronics and reduce the delay to 1 or 2 milliseconds. This is only possible because of the very sophisticated shutter mechanism built into Rollei lenses.
A further consideration in selecting cameras for high-speed applications is the ease with which a Polaroid back can be attached for making test shots. We use large amounts of Polaroid film when setting up shots.

Detection

Because the events to be photographed occur so rapidly, it is necessary to detect them electronically. While it is possible to use sound and vibration sensors in some situations, most often we rely on narrow infra red light beams being interrupted.

To ensure that the action is properly positioned in frame and also in focus, two intersecting beams can be used. As a further refinement, a third (gated) beam can be used to make certain that the subject is moving in the proper direction. This eliminates wasted shots of the back end of retreating animals.

Synchronization

When multiple beams are used, special electronics are required to process the incoming signals. It is also necessary in some situations to introduce a short, but precise, delay into the response. Once again, we have our own circuitry to handle these requirements.

Photographic Data

Most of our stop-action images are taken on 100 ISO film at 1/40,000 second and a stop of between f/11 and f/22.