Vesa Perala wrote:
>
> Sorry, I checked 100-400@100mm (f4.5) only when EOS-3 was set for
> half-stop scale (it was around 2 a.m. anyway when I made the tests).
> I may do (just for "theoretical interest") it once more with
> 1/3-scale selected and see how the jumps are between 5.6 - 5 - 4.5.
>
> IF f3.5 is f4 + half-stop it is also interesting to see if f3.5
> at 1/2 and 1/3-scales is equal or not.
>
I think you already did a plenty good job, but yes, this would be
particularly interesting.
I don't think they are equal. If they were, what would f4 + 2/3
stop be with 1/3 scales? ;-) What I can't figure out yet is the
following: A nominal f/2 lens can be set to f/4.5 on both,
1/2 and 1/3 scales. And I suppose it means 1/2 and 1/3 stop
closed down from f/4 in these cases. But I can't imagine an f/4.5
lens could not be stopped down to f/4.5 (=1/3 stop from f/4) with
a 1/2 scale. It has to be possible somehow ;-) Otherwise it would
be a waste of lens speed and the lens would be faster when used
with an 1/3 scale than it would be with an 1/2 scale.
Confusing ... :-(
Thomas Bantel
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