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RE: [OM] More Calcs on Flash GN

Subject: RE: [OM] More Calcs on Flash GN
From: HI100@xxxxxxx
Date: Wed, 8 Mar 2000 16:55:02 EST
Chip corrected an erroneous assumption in my previous post by pointing out that 
:
" Except  that  the T20 only gives coverage for a 35mm lens."  I had not 
checked the T20 spec and assumed the coverage was the same as the T32's (24mm ).

Since the area covered by the flash goes up by about the angle of coverage 
squared and the angle of coverage for a 24mm is about 1.3 times that for the 
35mm the area covered by the T20 is smaller by a factor of 1.3^2 = 1.7 thus the 
overall flash efficiency from stored energy to light output for the T20 is 
about 1/1.7 = 600f the T32 . Interesting, is it the reflector or the tube or a 
bit of both?

         >>  Tim Hughes  <<

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