The 35-80 2.8 shows the same behavior if I remember correctly.
Iwert
2011/12/21 <usher99@xxxxxxx>
> >I need the advice of the Zuiko F5/50-250 zoom owners:
> >Since I am new to this lens, I noticed that when attaching it to the
> >camera body in the 50 mm focal length position it visually stops down
> >the aperture slightly.
>
>
> Just checked mine. It is constructed in a similar fashion as the Zuiko
> 135 macro-that is more well known to stop down a tad
> even at F4.5 as it is F4 when mounted. I was confused by the wording.
> If mounted on OM the Zuiko f5 50-25 must be faster than F5
> but only stops down more on OM when the aperture is triggered even at
> F5. Things are more complicated however as it is a constant aperture
> zoom vs fixed FL The physical size of the aperture also changes some
> while zooming of course to result in F5 at the various FL's. Not sure
> how unusual the extra stop down with aperture triggering at "wide open"
> setting really is on such zooms. If the Z. zoom is mounted on OM5DII
> with adapter and stop down pin it will of course be F5 wide open and
> the Slightly brighter VF will be lost and the narrower depth of focus.
> I bet the Z. 135 is very unusal in design in that regard.
> .
>
>
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