Divide the long edge of the rectangle into four equal sections. as shown. Use your knife to score the cardboard along each of the lines. Fold the cardboard along the scores to make an open-ended box.
Before you tape the edges together to make a box, you need to make the interior black to minimize reflection of light within the camera. You can cut a piece of black paper and fold it to make a black lining for your box, or you can cover the inside surface of the cardboard with strips of black tape. You could also paint the inside flat black with spray paint or tempera.
Now tape the edges together to make a box, and tape all the box's edges and corners to prevent light from leaking into the camera.
Insert the box into the film cartridge as shown. It should fit tightly. When you hold the open end of the box up to your eye, you shouldn't see any light leaking in where the box fits into the cartridge.
To make the front of the camera, cut a rectangle of cardboard that measures about 1 3/4 by 3 inches. Cut a square hole that measures about 1/2 inch by 1/2 inch in the center of the rectangle. Line the inside of the front of the box with black paper or tape, leaving the hole open.
Tape a 1-inch square of aluminum foil over the square hole, and make a small pinhole in the center of the foil.
When you aren't taking a picture, you need to cover the pinhole with black paper. We made a shutter that slides into black paper guides. as shown.
To ensure that no light can leak in, tape the box to the front with black tape. Fasten the camera to the cartridge with rubber bands, as shown.
To get a sharp photo, it's important to hold your pinhole camera steady To keep the camera steady. one of our staff suggested that you "tape it to a brick." He attached his pinhole camera to a tripod with rubber bands.
Using ASA 200 film in bright sunlight, we found that we got good pictures with exposure times varving from one to three seconds. The ideal exposure time will depend on the size of your pinhole and the brightness of the day. Experiment with different exposure times, and you'll learn which times give the best results.
After each photo. advance the film until the third and fourth number in the series of frame numbers appear in the window. When you've finished the roll, you can take your film to a commercial photoprocessor for developing.