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28 May 2004 Photographing insects in flight with a high- speed flash Ted Kinsman
For many years I have been involved with high speed photography and have modified a number of flash systems to operate at faster speeds. These modification are often complicated, time consuming and, because of the high voltages involved, dangerous. Lately, a new flash manufacturer, Fotronix, has started producing flash units that operate at 1/15,000 of a second. This speed is fast enough to freeze the motion of birds and insects. The Fotronix flash units are highly reliable and allow the technical photographer to concentrate on other aspects of a photo shoot than wondering if a flash unit trigger or not. For this article I will go over some of the basics for a setup to capture insects in flight. Flight tunnels designed for the photography of insects need a way to confine and sense the location of the insect. They also need a method to trigger a high-speed flash when the insect is at the correct location.
I have built several experimental flight tunnels out of cardboard. When I am satisfied with the design, I will build a better tunnel out of a more durable material. The tunnel is separated into two parts. The back part of the tunnel contains a background and a glass window for the external flash to illuminate the background. The separation between the two compartments is where the trigger system is located. Two red solid state lasers, salvaged from laser pointers are used to make a large cross pattern. The laser beams are detected by photodiodes. When both laser beams are broken at the same time, a circuit connected to the photodiodes sends a high TTL pulse to a microprocessor that controls the flash units. The microprocessor is a special processor manufactured specifically for high speed flash applications by Mumford Microsystems (see below). This unit is called the Time-Machine. It can control delays, as well as accept about 8 different sensors.
For a number of years I have collected live caterpillars of the polyphemus moth (Antheraea polyphemus) in the fall. These caterpillars quickly build a cocoon and winter over in my basement. In the spring, to the wonderment of my children, the moths emerge. The large moths always seem to emerge within a few days of May 15 in Upstate New York. This year a large male emerged from his cocoon about 3 pm in the afternoon. By 9 pm he was ready to fly. So I placed him in the rear compartment of the flight tunnel. I used the open flash technique, in which a digital camera was placed in front of the tunnel and the camera was focused a centimeter in front of the laser trigger spot. The camera was set to the "bulb" setting, and the shuuter was left open until the moth triggered the flash. The the shutter was then closed. The moth flew right toward the camera several times, and some of the results are shown nearby. After six flights in the tunnel, it was time to let the moth go. This particular individual was a male (as determined by its large antenna). The antennae are very sensitive chemical detectors that can sense a female moth from several kilometers away. The adults lack mouth parts, so they do not eat during the three or four days of their adult life. I should mention the moth was enticed to fly in the direction of the camera due to a dim light placed behind the camera. Different kinds of insects can be enticed to fly by using UV lights, heat, or air flow.
I hope that this short note has provided a quick overview of the process and inspired readers to try their hand at photographing insects in flight. For more information about high-speed flash systems, see www.fotronix.com See Camera Microprocessor Controllers at www.bmumford.com My personal page on high-speed photography is at |
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Copyright 2004 by Society for Amateur
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