Sounds right to me, the two f8 shots are slightly underexposed relative
to the f6.3 shot, just as one would expect. I assume you were on manual,
otherwise, the auto-exposure should have evened up the exposures by
using a 'between' shutter speed. I don't know what camera you were
using, but most only show full stop differences between speeds. Thus
anything up to 1/2 stop over or under 1/500 will show as 1/500. Since
the difference between f8 and f6.3 is less than 2/3 of a stop, both
stops could give the same speed indication, with one slightly over and
the other slightly under. Considering that meter, lenses and converters
are all subject to variation around nominal values, this all sounds
right on the money.
Moose
frieder.faig@xxxxxxxxxxxxxxxxxxxxxxxxx wrote:
I´ve just made a comparison between F4/200 + 2xA =F8/400mm and a
F4.5/300 + 1.4xA = F6.3/420mm. I was wondering, wide open, both lenses
achieved 1/500 second altough the 300+1.4 combo should be a half stop
faster. So I´ve made three slides, 200@F4(=8), 300@4.5(=6.3) and 300@5.6(=8).
All with 1/500sec, which was meassured at F8 with the 200mm lens, and at F6.3
with the 300mm lens (??).Result: the second slide is a bit brighter than the other two,
which are equal in brightness.
Sems at one of these lenses/converters the apperture lever isn`t adjusted
propperly.
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