Gary,
The ready made pinhole body caps are laser drilled in foil. They sell for about $33 plus shipping from one particular MFR,
Lenox Laser.
One can make the pinhole by a pin through aluminum or brass foil or else buy it in a body cap for Nikon, Canon or other camera with removable lens. Mark Uliasz finishes images off in photoshop
here and the pics are quite pretty.
Originally Published in DigitalniFoto Magazine, by Dennison Bertram
Here's a way of keeping dust out of you lens cap pinhole:
Here's a fun instructional video
Digital Pinhole Photography. This is just a decently nerdy background.
Here's the very simple formulae for calculating anything you want and a small software program for Mac or PC computers to calculate exposure based on B&W film. I simply use the 5D to determine the required exposure and then change that to say f 180 to get the exposure time (use the calculated f stop for the pinhole size and focal length used.) If it's for the digital camera, adjust shutter speed based on the LCD image and histogram.
In practice, for film* there's tons of latitude and it works. For digital, of course, it's so much easier!
Asher
*For film, one needs to add extra seconds to calculated exposure time whenever one uses long exposures. This is required to account for "reciprocity failure" of the emulsion, meaning further photons effect less silver ions and so one needs to progressively expand the time. There are simple tables for this for each film you might use.