A pinhole camera is the most basic form of a camera, it has no lens. A small pin prick hole acts as your lens and aperture, letting in light and exposing a piece of photo paper placed inside. Pinhole cameras can be made from many kinds of light-tight containers. A cylindrical cardboard container, such as an oatmeal box or a coffee tin, can be easily converted into a pinhole camera that use pieces of photographic paper.
First, spray the entire inside of the can with flat black paint including the lid.
On the can's side, locate the approximate middle point and very lightly mark it.
Using a very small needle put the point on the mark and begin to work the needle through the cardboard side of your can by turning the needle back and forth as if it were a screwdriver.
Stop as soon as the needle just pokes through the other side.
Use your piece of sandpaper on the inside of the container to sand away any edges around the pinhole.
Now cut a 1 inch X 1 inch square out of your index card or posterboard.
Place the square over the pinhole on the outside of the container. Tape down one side of the square so that it can be lifted up and laid down like a flap. This will be your camera's shutter. Keep the flap held down in place with a rubber band when it is not in use. When you do take a picture you will remove the rubber band, open the flap for the necessary exposure and then close it again.
Take your camera into a completely darkened room and place a 4"x6" cut piece of photo paper into the canister emulsion side (shiny side) facing out toward the pinhole.
Close up the canister tightly and take it out to a brightly lit environment to take your picture.
Face the pinhole side toward the subject you want to photograph.
Remove the rubber band holding the shutter flap and open it all the way (you may have to tape it down to keep it open).
After about one minute of exposure close the flap again and fasten it down.
Take out the piece of photo paper in a dark room and process.
You will need to experiment a lot with the amount of time you leave open your shutter. Try several shots of the same scene with varying exposure times to get a good idea of how your pinhole camera captures light.
Photographic paper is light sensitive and will be ruined if it is exposed to direct light outside of a container.