Re: SV: pinhole size

At 08:48 AM 7/22/2002 +0200, you wrote:
>Haven't tried it myself, but I guess it would work:
>
>in your darkroom , you place a transparent ruler somehow in your enlarger
>and mark the mm-steps on a paper.
>Then placing the pinhole-plate in the enlarger, you see if its round and get
>an approximation of the size.
>
>Perhaps you might get an exact measuring doing some maths on the enlargers
>height etc - but thats' beyond my skills for sure.
>
>/peter

I've used a transparent ruler this way also, but have found that the ruler
is a bit "fuzzy" when projected. As an improvement to this, I made a scale
of 2mm, divided into 1/10th markings (in Photoshop). I printed this onto
transparency film. Then I cut it to fit into the enlarger. Once in the
enlarger, move the enlarger up or down to project the 1mm onto 1cm of the
ruler on the stand. The enlarger is then calibrated. If you cut your
brass shim (or whatever strata you are using for the pinhole) to fit the
enlarger film holder, you can now insert it and measure its size on the
ruler on the stand. I hope this explanation makes sense. I've used this
in a couple of workshops I've done (as a more advanced thing you can do),
and it produced very accurate pinholes for everyone. I think a magnifier
like a Lupe is perfect for checking how well made the hole is, but the
enlarger gives a pretty good measure of its size.

Here's a pdf version of it if anyone would like to use it:
ftp://ftp.pinhole.com/pinholeSizeProjection.pdf

- Gregg
Received on Mon Jul 22 06:59:25 2002