C.H.Ling wrote:
>
> I think it is to compensate for the fall off at widest aperture. Light fall
> off is quite high for most large aperture lens, especially standard to wide
> angle.
>
> C.H.Ling
>
This sounds very reasonable to me, especially as it seems like the phenomenon
is much more pronounced in wide angle lenses. I have dug out my caliper
and have made a few measurements on the step intervals on a 35mm f2 and
a 200mm f4 lens. I have measured on the lever on the rear side of the lens.
The 35 mm moves the lever 1.4 mm from f:2 to f:2.8 and 2.8mm from f:2.8 to
f:4.0. The step from f:4.0 to f:5.6 is 3.1mm.
The 200mm moves the lever 2.4mm from f:4 to f:5.6. The next steps are 2.9mm
and 3.1mm.
While this is somewhat crude, I think it is essentially correct.
BTW, I had also noticed and wondered at the odd interval, especially in
view of the claimed precision of the light meter in the OM3 and 4.
Regards
Lars
--
Lars Haven <mailto:lhaven@xxxxxxxxxxxx> http://isa.dknet.dk/~lhaven
"When writing about women, one must dip one's pen in a rainbow"
D. Diderot
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