The PINH5AD is a 3D printed Pinhole Camera, focal length 90mm, designed for a 0.40mm pinhole, with an f/stop of f/255. The P5 is designed around a 4x5 film holder, widely available used or surplus. Film holders have a "dark slide" that protects unexposed film/paper from light, so a rubber band to close the shutter is not necessary (or desirable for long exposures).
I plan to design a system for swapping extensions for a more flexible camera system. Using a film back would allow you to do this in the field without exposing your raw film. Stay tuned for updates!
90mm focal length
designed for a 0.40mm pinhole
f-stop of f/225
70 degree field of view
Originally designed for extruder-type 3D printers, and to be printed in black ABS, you can order one here if you don't have access to your own printer. Assembly is largely the same, but (in black) the interior surfaces might benefit from a coat of flat black paint or India ink for maximum light-proofness. If you order it in white, be prepared to apply several coats of black paint to all surfaces.The surface of the film bracket will benefit from self-adhesive black velvet for a proper light-tight fit.
More information here: http://www.thingiverse.com/thing:143882