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Author Message   Arfd Tinkerer Username: Arfd Post Number: 27 Registered: 01-2013 Rating: N/A Votes: 0 Posted on Monday, July 29, 2013 - 03:01 am:    You will need a standard light source. It is not difficult to make, Tomosy in Book 1 gives details, and there is also a description in the instruments / tools section of this forum. The secret is to calibrate the light against a camera known to be giving correct meter readings. The adjusting screw for low light levels is mainly to compensate for slackness in the coupling cord and can often be left alone. It is surprising that those members of the forum who are gifted in the electronic arts haven't published details about making a circuit to deliver a stabilized voltage from an unstable battery voltage. A simple diode isn't any good. Come on guys, it's not rocket science.