Dissect & Modify the Camera
The first step is to open and inspect the camera body. If your camera has a flash unit, you must open the covers very cautiously to avoid electrical shock. As described by Byrd and Graham, the flash unit contains a large capacitor (120-160 micro-farads rated for 330 volts), which can retain its electrical charge long after the battery has been removed and can be quite dangerous if not discharged thoroughly. Do not use the flash units for this activity unless you can be sure the students will avoid touching the internal circuit board. Once the camera is opened, you can "short" the cylindrical capacitor using an insulated piece of metal to connect both leads to each other. It is important to short the capacitor several times and to be sure the battery has been removed from the side compartment.
Notice that there are snap locks on both sides of the camera body, one of which should already be open since it contained the film removed by the developer. To open the camera body, peel back some of the yellow sticker identifying the camera as KODAK on the top and bottom of the camera and unsnap the plastic pieces. The top and bottom should separate without much force. You should now have four pieces: the front cover, back cover, middle (main camera with lens), and a cylindrical spool.
The shutter mechanism must be removed for long-exposure photography. You need to remove the lens assembly temporarily. The lens is mounted in a black plastic housing which can be pulled off from one corner once you have removed a "C-shaped" metallic band. The latter may not be present in all cameras and can be discarded once removed. Avoid touching the lens; your fingerprints could deposit an oily film or scratch the lens surface and ruin its focusing ability. Dust on the lens can be removed by blowing air sideways across the lens. Once the lens assembly has been removed, you should see the shutter mechanism: a dark gray metallic piece hinged to a small plastic post and also connected to a spring. Remove the spring and the gray piece. Replace the lens assembly by locating it back on its plastic locating posts and snapping it back into place. Replace the front cover of the camera.
If you plan to do this activity with a large class, go to a photo-finishing store and ask to collect their disposable camera bodies. For loading new film, as described below, you should also acquire the used film canisters with the toothed spindle. WalMart has been very generous to us -- they will let you sort through their recycling bags for the specific items you need.
Loading the Film
Since the disposable cameras do not have a rewind mechanism, they operate backwards from an ordinary 35-mm camera. You will put the film in the camera so that, as you take pictures, the film is rolled into its canister which can later be removed for processing. From a camera store you can buy a roll of film and re-rollable film canisters (30-60 cents each) with screw-tops. You don't need a full roll of film for each camera. We generally figure three to four cameras per roll of film (36 exposures), putting six pictures on each camera with an extra one to two frames needed to attach the film with lag and lead.
Figure 2. A disassembled One-Time Use camera with its internal components shown to the sides. Also shown are the items necessary for reloading these cameras with film. Photo courtesy of the authors.
The following procedure should be done in total darkness. You can practice in the light with previously exposed film, making careful mental notes and paying close attention to the feel of the following steps. Figure 2 illustrates the components discussed below.
Occasionally, the side doors (for film and battery) detach from the camera body due to fatigue in the plastic upon repeated bending. We have found that these doors can still snap back in place and that they can be sealed against light-leaks by using electrical tape to fasten them to the camera body.
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