Quote Originally Posted by little golan View Post
I am ready with three pinhole cameras for the world day. Using the 'pinhole calculator' I have the f # and the exposure factors. I have a light metre that will let me say iso 3.2.... but I cant quite understand how to change my information into exposure times. I could use film, I can use the calculator for that, but I want to use paper. So can anyone help me tranlate it?
F333 / exp factor 229.1
F230 / exp factor 109.3
F358 / exp factor 264.8.
Assuming you are talking about Pinhole Designer, the idea is to see what shutter speed your lightmeter shows for f22, then multiply that by the exposure factor.

Reading: 1/25 ( = 0.04 seconds) @ f22
x 229 = 9.16 seconds @ f333.

Note that many films exhibit reciprocity failure at long exposures, so even more time than the calculated value may be needed. Paper may have less of a problem, I've never tried it.

The important thing is that if you get anywhere near close, you should get something usable. From what I've read over the past year or so, an ISO index down around 3.2 to 6 is likely a good place to start for paper.