On Thu, 8 Apr 2010, Carlos J. Santisteban wrote:
>> Olympus has designed the lens so that the travel of the aperture lever
> inthe >lens mount is less than one stop when going from wide open to f/2, to
>> keep the metering accurate.
>
> I don't understand this... just tried the OM-1 and it meters reciprocally at
> any aperture _except_ the widest, which reads about half a stop under (after
> selecting a one stop faster speed). Tested with 50/1.2, 40/2 and 100/2.8.
> Also tried the 135/3.5 and seemed reciprocal... but if I select one stop
> faster speed while going from 5.6 to 3.5, it _should_ read a bit over, no
> equal exposure! So, no compensation is done for the small first stop, anyway
> :-(
Yes, I think I was trying to say essentially the same thing. But what I
also meant to suggest was that the small first stop is *itself* a form of
compensation, not the other way around. We need to meter for all possible
apertures between f/2 and f/16 (when talking about the 50mm) and to do so
Olympus has decided to increase the exposure *less* than one stop just for
the first step from wide open to the next click on the ring.
I don't know why this compensation would be needed. A naive explanation is
that the lens is actually that much slower than advertised wide open, but
that doesn't fit with what Moose posted later about the measured aperture
published in a photo magazine test (1.44).
Priit.
--
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