[pure-silver] Magnification - Exposure compensation ruler
- From: "Nicholas O. Lindan" <nolindan@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Mon, 12 Nov 2007 10:25:22 -0500
Darkroom Automation's support web site has a file to
help determine the required exposure correction for
magnification changes.
The ruler measures square-law light fall-off in stops.
Simple subtraction of the new and old measurements
yields the required exposure correction - no dividing,
no squaring, no logarithms.
http://www.darkroomautomation.com/support/stopsruler.pdf
If great accuracy is needed then an exposure meter
should be used. Different enlargers require different
corrections for the non-square-law light fall off from the
condenser or diffuser to the lens - this is only critical
at small magnifications.
--
Nicholas O. Lindan
Cleveland Engineering Design, LLC
Cleveland, Ohio 44121
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