Drink a canned beer (or energy drink). The 16-ounce aluminum tallboy size is what you want because a curled 5-by-7-inch sheet of photo paper fits inside, leaving just the right gap for your pinhole.
Cut the top off with a regular can opener. Be careful not to cut yourself. Wash and dry the can.
Spray the inside of the can with flat black paint to avoid reflections bouncing around inside.
Poke a tiny hole in the side of the can with a needle or pin—the smaller, the better for the sharpest image. I usually go at least a half-inch or so above center.
Sand the aluminum burs off the pinhole, both inside and out, with emery paper—the smoother, the better.
Cover the pinhole on the outside of the can with a little piece of black duct tape for a shutter. (I recommend duct tape for everything. I think it’s one of the great inventions of the world—that and epoxy.)
DO NOT DO THIS IN SUNLIGHT: Curl a sheet of 5-by-7-inch black-and-white darkroom photo paper to fit inside the can, with the emulsion side facing the pinhole. (I use Ilford Multigrade IV RC Deluxe Pearl. A matte or nonglossy surface is best.)
Secure the paper to the inside of the can at the top rim with a couple of little pieces of ol’ Brother Duck, making sure you don’t accidentally cover the pinhole. You can do this in the dim light of a bathroom or closet if you’re relatively quick without exposing the paper (ISO 12 or thereabouts).
Cover the opened top of the now loaded can with a little piece of tin foil, then cover that with a crisscross of ol’ Brother Duck. About six or eight pieces works for me.
Justin Quinnell, my overseas mentor, makes a very nice cap you can put on and off the can at your pleasure (he shows how on his website).
Now you have a six-month duration pinhole camera.
Incidentally, you don’t have to always make your pinhole cameras out of beer cans. I’ve made dozens of them out of 35 mm film canisters and mailing tubes and cookie tins, etc. All you have to do is snip a little rectangle of aluminum out of a beer or soda can, then poke a little pinhole in it and duct tape it in front of the hole you make in the side of whatever container you’ve chosen for a camera. Of course you’ll have to cut a piece of photographic paper to fit.
I’ve also made pinhole cameras out of 8-inch lengths of 3-inch-diameter PVC pipe. The cows can’t chomp them to pieces, and I always put them higher in the trees than the feral hogs can reach. Thankfully the PVC is also too strong to accidentally crush when you pull too tight on the duct tape while taping them to a tree or post, as sometimes happens with the weaker aluminum beer cans. Also they make PVC caps for top and bottom, so it’s a snap to load and unload your paper.