Stop calling me Rand its insulting. I dont care what it means in british slang.
On Apr 2, 2014 2:01 PM, "karl shah-jenner" <shahjen@xxxxxxxxxxxx> wrote:
Rand:
Seiko shutter mamiya sekor 80mm f2.8 30th to 500th range. Tested at all
speeds at f22 and f2.8. Mamiya afd iii with leaf aptus 65s. Metered with
gossen ultraspot 2 flash meter 4 and I camera matrix meter. Deviations are
in stops (ExIN). 30th at f22 +.22. at 500th at f2.8 is was +.17 a
30th at 2.8 was .01%+ a 500th @ f22 (smallest the lens gets) +.27 So
the difference at a 500th from f2.8 to f22 is +.1 so even if you
extrapolate that out to f45 which is 2 more stops you get to a difference
of .13 (a gain of .03 stops) stops from 2.8 to 45. or f45@ a 500th would
be +.273 stops.
you seem to be missing the point I wrote when I said:
Of course the easy way to test and see for sure is to use the soundcard
(microphone input) on a computer and record the shutter speed for
evaluation.. bearing in mind that leaf shutter speeds are pigish things.
where do you measure the speed? the center of the lens? the edge? if near
the edge are you measuring under an opeing blade or a point where the blade
moves ou the way quickest?
I was talking of the duration of the shutter opening. f45, f2, the time they are open will be different. you've appeared to misunderstand and measure overall exposure. I am unaware of anyone measuring shutter duration with a light meter.
However I also said:
Best bet is in the middle witha diffuser under the lens, then look at the
soundcard output and work from when the lens is allowing about 50% of the
light through to when it's closed of to 50% of the light.., or 30% depending
who you ask =D
Andy seemed to suggest he preferred 50%.
