Originally posted by Catalana Thank you for this explanation. It made a lot of sense and gave me quite an insight. Much appreciated. Just out of curiosity, what would the diameter of a f/180 pinhole be for the body cap. I wouldn't mind experimenting.
I'll guess that it's around 0.25mm. Normally I would refer to my favorite fat PDF on the subject,
Pinhole Photography by Eric Renner, but I can't access that right now, so I'll just recommend
this Wikipedia page which has links to pinholing how-to's.
NOTE: making pinholes for 135/FF and 135/HF (APS-C) frames is tricky because the hole's edges must be PERFECTLY SMOOTH to avoid nasty diffraction effects. Laser-punched holes are best. The optical path needs to be PERFECTLY CLEAN or you'll get the same shots I do: prominent dust. And because of the register problem I mentioned above, body-cap pinholes will have focal lengths around 'normal' with 135/HF (APS-C) frames. A 135/FF rangefinder could have have its lens removed and replaced with an inset pinhole for a wider angle... which would probably include the lens mount framing all images. Better to get a pinhole Holga.
Pinhole cameras (PC's) exist in a wide range of sizes, from surveillance pinheads to modded aircraft hangars. I've suggested roofing over Arizona's Meteor Crater, or nuking an iron-nickel asteroid into a giant cylinder, to get large-scale PC's. On a human scale, some people put bits of film into their mouths or fists as make-do PC's. Camera-obscura and pinhole photography really are lots of fun, but I prefer larger formats than our digicams allow. Get thee to an oatmeal box, eh?