Re: Pinhole sharpness.

Cees de Groot (
15 Jul 1997 15:42:41 +0200

fisheye <> said:
>hole in the stock. A clean hole is also very important. Sand doun any burrs and use a
>magnifying glass to inspect the edges around the hole. It should be round and clean.

I used my enlarger and grain focusser to do the final inspection. You might
want to save yourself a lot of work, however, and order a complete set of
pinholes from The Pinhole Resource (
or (505) 536-9942), they also have sheets of brass shim and fine (#600) sanding
paper if you insist on doing it yourself. I ordered their set of 12 different
sized pinholes and mounted them in 35mm slide frames - probably a life-long
investment (US$28.00 postpaid :-)).

BTW, original poster: you didn't mention the format you used. Note that
Pinhole images are never sharp. A pinhole projects dots around its own
size on the negative (at least, that's how I picked it up), so making the
pinhole smaller (up to diffraction limits) and the negative bigger (like
8x10" paper instead of 35mm negative material) will make your image seem
sharper as well.

Theory section: for lens-like sharpness, you'd need a pinhole about
1/1500th of the diagonal of the film format. So for 8x10", you'd need
a pinhole of 12.8"/1500 ~= 0.0083". A pinhole this small must be used
close to the negative in order to reduce the visibility of diffraction
effects, somewhere around 35mm (depending on the formula you happen to
use). That gives an angle of view of around 160 degrees - comparable
to a 5mm lens for the 35mm format. Smaller angles of view need larger
pinholes (in order to keep the effects of diffraction low), meaning a
larger circle of confusion, meaning less sharp pictures. So don't
expect too much here.

Pinhole photography: long, sharp - choose one.

Disclaimer: my math is rusty. And please correct me if I'm wrong in any of
my assumptions, most of them are speculations :-).


Cees de Groot              <>
Principal Consultant
OpenLink Software    <>