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Method and Setup |
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Equipment Cameras: -Sony DKC-FP3 Digital Still Camera w/ tripod -Nikon D1 w/ 55mm micro lens Digital Still Camera w/ tripod -8 Vivitar 283 flash units -Color filters for flash units -Apple II + computer -Apple game port Interface -Sound Trigger -Television -Black Backdrop -BB gun -Copperhead 0.177 cal. BBs -BB Stopper -Rubber band suspension frame -Rubber Bands -Safety Goggles Equipment Setup Our lab area is fairly long. We have a table that spans across the wall and this is where we placed our BB gun. To maintain accuracy we placed heavy lead blocks on the table to set the gun on, and marked specific areas to keep a reference for gun placement. At the other end of the counter, is the pellet trap, and between the pellet trap and the gun is a rubber band suspension frame that we built. The distance from the gun to the rubber band suspension stand is approximately 1 meter and another meter separates the pellet trap and the frame. Perpendicular to the RB frame is a series of eight flash units placed on a table side by side at a total length of 0.75 meters. The flash unit table is 0.6 meters from the RB frame. Our camera, which is on a tripod, views over top of the flash units and is 1.2 meters from the RB frame. The Apple II + sits to the left of the camera, and the television monitor sits to the right, providing a great ergonomic working area for the cameraman to operate everything.1 The other person has a small area at the gun, where rubber bands are prepared to be hung on the frame for the next shot.
Our set-up.
Armed with 8 of these baby's aint nuttin gonna stop us.
Let's take another look at this world-famous set-up.
Paul aiming the artillery.
Stew, in the process of "acting like he's doing something" so Dr. Winters can take a purty picture.
Paul calculating velocity's on crack, way to go Paul, keep up the good work. Description of triggering, timing, and imaging methods Our intention was to capture an image with one BB traveling through three evenly spaced rubber bands one after the other. We used eight flashes to capture eight sequential images of the BB in flight, which in the picture would be superimposed over one another. We needed to time our eight flashes in very specific way to go off twice before and twice after each rubber band. This spacing was a necessity for our image analysis calculations. We used dvat’s to get a rough estimate on how close we could space our rubber bands and still achieve the two images before and after every rubber band. After this we had to experiment with different time intervals, we estimated with physics formulas to see how close we were to being correct. Our Apple II + computer uses a program called Multiplexer that allows us to type in specific times for delay (the time between the input the sound trigger receives and the first flash) and flash intervals (time between each successive flash). For example, a common delay we used when the gun was pumped seven times, was approximately 4ms, and the interval was usually between 0.2 and 0.4 ms. The special interface that we used for the Apple II + , was an Apple II + game port which has the capability to control 16 flash units. This box relays the input from the sound trigger to the computer, which controls the timing, and then back out to the flash units. Description of experimental method The person who shot the gun was in charge of preparing rubber bands. The rubber bands were cut to make a long strand and tacked at each end in preparation to be pinned to the frame, always at equal intervals. The three tacks that can be seen in the photographs were usually made sure to be different colors in order to help people realize that there are actually three different rubber bands being shot. The gun was aimed to the side of the frame setting the timing, once this was correct we would aim the gun through all three bands and prepare to shoot. We would then turn out the lights and set the computer to wait for an input to the sound trigger. When ready, we would count down from "five". At "two", the photographer would press the shutter, and on "one" the shooter would squeeze the trigger. |
