Quote Originally Posted by Ole
Quote Originally Posted by Ed Sukach
I don't think this would work - the theory behind the "pinhole" is to diffract the light passing through to the extent that it would give a "lens- like" effect... bending the rays to a "pseudo" focus plane. I've tried measuring small spaces on a Optical Comparator, and the edges become *extremely* fuzzy and indistinct. If they did not, it is likely that the "pinhole" is too large for use.
Not quite, Ed...
The theory is that light moves only in straight lines through air - excepting diffraction. so a light ray from upper left would hit the lower right corner of the film, and nothing else. Moving the pinhole in and out affects only the effective focal length (and thus aperture), not focus.
Diffraction is what kills sharpness in pinhole photography, otherwise a smaller hole would always give sharper pictures.
Oh, I agree with the "not quite". I will point out that the study of diffraction and the way the wave propagation affects the light ray paths is complex and would require a "course of study" FAR beyond the scope of concise messages here. That is why I tried to cover my gluteous maximus by using the "pseudo" before the "focus". The "pseudo" does not appear to have been very successful.

BTW .. "diffraction kills sharpness" - is true - but without it, "pinhole" would not work at all.