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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