Materials: sewing needle, thin brass shim material, emery paper, measuring loupe, opaque tape, sharpie pen, cardboard. [another source of thin metal is soft drink cans, approximately 0.004" thick]
1) cut out a 1 inch square of brass shim and place on cardboard
2) gently push the sewing needle into the brass, but not all the way through
3) sand paper the "bump" on other side of the brass
4) repeat steps 2 & 3 until a very small hole is produced
5) measure the size of the hole with the measuring loupe. You can always make a hole larger, but you cannot make it smaller.
6) blacken brass around the hole and tape onto camera
7) calculate the f-stop and use the camera [f-stop = distance to the film divided by the diameter of the pinhole]
NOTES:
Step #4. If you go back and forth to BOTH sides, you will actually make a better pinhole. [the thinnest part of the hole will be in the center of the foil instead of off to one face]
Step #6. It turns out the Rapid Selenium Toner and Polytoner from Kodak will blacken brass and copper. Just dip into the solution for a few seconds, rinse and dry. No possibility of accidentally covering the whole with dried ink. [worked out with Murray Leshner 4/27/2004]