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Re: [OM] 21/3.5 an interesting lens

Subject: Re: [OM] 21/3.5 an interesting lens
From: frieder.faig@xxxxxxxxxxxxxxxxxxxxxxxxx
Date: Thu, 7 Mar 2002 17:02:50 +0100
On Wed, Mar 06, 2002 at 09:56:28PM -0800, M. Lloyd wrote:
> If Diffraction is bad at f22, why does the 24 shift
> have a stop at f22 considering that it is also an f3.5
> and in my totally unscientific tests I have found no
> difference between f16 and f22 on that lens; neither
> did Gary Reese (Yes I know these lenses have little in
> common other than their f-stop and wide angle nature
> I'm asking a stupid question but still...)
> 

I assume diffraction reasons too. Diffraction impact
also depends on the angel of field. The diffraction limit
goes down, when the light comes more off axis.
This is why tele-lenses can be stopped down further 
than wide-angel lenses. 
The 21mm- Zuiko`s offers pretty well close focusing 
capabilitiers this also increases trouble with diffraction. 
At infinity F22 might be o.k. for average quality 
standarts, but at close distance I`d bet the 
image would be soft. 

The close focusing distance of the 24mm shift is longer
than on the normal wides. This would make sense.
The 2.8/ 28mm is the only Zuiko wide angle lens offering
F22 as smallest aperture. 
 
> Also how do you use filters with this thing? The 49mm
> filters I have exibit obvious vignetting in the
> viewfinder.

Polar-filter's? With normal UV/Sklight...-filters I´ve
noticed no serious trouble when I´was using a 3.5/21.

Frieder Faig


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