High Speed Flash Photography
High speed flash photography has become a fairly common solution to various problems that arise in motion study and even machine design and malfunction diagnosis.
The term "high speed" is related to the recording on film of a fast moving event or object. The duration of the flash must be carefully controlled, predictable and as fast as possible to prevent blur due to motion. Acceptable exposure of the image must also be considered. Commonly available professional flash units, with slight modifications, can be used to attain flash durationís approaching 1/40,000 of a second.
The first photographs shown are of a light bulb being shot by a pellet. For these photographs a Vivitar flash unit was used. A fiber optic cable was adapted to feed light from the flash tube down to the units optical sensor. This adaptation effectively fools the flash unit into thinking that there is sufficient light in the room to make an adequate exposure. In this, and most other small flash systems, when there is plenty of ambient light, the unit will use a very fast flash duration to maintain correct exposure and extend battery life. The fiber optic cable assures us of a reliable and predictable amount of bright light entering the sensor from the flash tube, to enjoy the full benefit of this feature.
A sound trigger was used for the pictures of the light bulb being shot by a pellet. The trigger was set to trip the flash as the pellet exited the light bulb. In the first shot you will see shards of glass exiting the bulb (left) and the pellet is barely visible at the exit point inside the mass of glass fragments. In the second photo the pellet is plainly visible on the exit side (left) while fewer glass fragments are visible.
In the second series of photographs, a small droplet of milk was photographed as it hit a puddle of milk in a shallow container. A delay trigger was used on this photo to trigger the flash. While setting up the shot, milk was repeatedly dripped from a constant distance above the container and the timing was carefully adjusted to provide the correct delay. A laser trigger, with the beam adjusted to catch the drip, provided a trip signal to the delay at a point above the scene.
High speed Kodak T-Max 3200 film was used to record the events, then developed at the recommended time in Kodakís environmentally friendly Elon developer.
The three photographs shown were taken for class assignments in Photo 111, a class in Advanced Photographic Techniques taught by Professor Don Box at College of DuPage in Glen Ellyn, IL.