Re: [OM] Question: aperture ring on Zuikos : uneven stops/gaps.

Subject: Re: [OM] Question: aperture ring on Zuikos : uneven stops/gaps.
From: DBellamy2k@xxxxxxx
Date: Fri, 24 Aug 2001 16:31:41 EDT
I asked a question:

<<  On some Zuiko lenses, for example the 35mm f/2 and the 85mm f/2, the 
 ring does not have an equal spacing for all the f-stops. The first gap 
 between f/2 and f/2.8 is smaller than the subsequent gaps. >>

Only Wayne H. gave an answer (thanks):
<< reported on this list before (probably before you joined Dave)
What I found was that for each stop change in aperture
I got a doubling of exposure time (as would be expected) for all apertures
EXCEPT when going from f1.4 to f2 where the time factor was about 1.5 >>

Now I'm off to the archives to look! ... Didn't find anything. Difficult to 
know what keywords to use. Anyway, anybody else got any info on this?

It occurred to me this evening that it might be one of those contradictions 
you get when you get to very fast lenses and/or very wide angles, that you 
have to decide whether the lens is focussing a flat plane oblect onto a flat 
plane image, even though things are in 3 dimensions and are 'spherical'.

Once you get to lenses at ~f/2 the differences between these scenarios become 
important, as they do when considering ultra-wides and fisheyes. Maybe some 
sort of correction is needed and it is incorporated into the first shorter 
f/stop gap, with all the others being set up to be equal.

Until I get another explanation, that is how I will view it!

Dave Bellamy.

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