From: Richard Knoppow (dickburk@ix.netcom.com)
Date: 07/11/02-03:08:46 PM Z
At 03:16 PM 07/11/2002 -0400, you wrote:
>While on the subject, any ideas on how to clean up/brighten up a funky old
>GG, like the ones on my Deardorff and Century?
>
Take it out and clean it thoroughly with diswashing detergent. It may have
gotten a coating of oily grunge on the ground side. I recently cleaned up
an old Speed Graphic which I at first thought had some sort of very coarse
ground glass on it, just dirt.
There is a trade off between image brightness and uniformity of
illumination for ground glass. The finer it is the more even the
illumination but the dimmer the overall image. Coarse GG willbe bright in
the center but have a serious hot spot in line with the lens.
About the only way to get even illumination is to use a field lens of
some sort. Even a cheap fresnel desk magnifier will brighten up the
corners, but is not very satisfactory.
Edmund Scientific (or maybe its Edmund Opticals) sells both good ground
glass and also inexpensive but quite satisfactory Fresnel lenses. The GG is
about $20 US. Smaller sheets are not much cheaper because of the labor of
cutting them from larger sheets.
---- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com
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