Archived posting to the Leica Users Group, 1997/06/25

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Subject: Re: Lens Diffraction
From: aglang@sprynet.com
Date: Wed, 25 Jun 1997 09:35:23 -0700

Nevertheless your resolution at f16 is certain to be worse than at f8 in a 
well-corrected lens like the Elmarit....

On Tue, 24 Jun 1997, Richard Clompus <rclompus@voicenet.com> wrote:
>aglang@sprynet.com asked about using f 22 on the 28mm Elmarit lens for
>prefocusing with the hyperfocal distance:
> 
>>but wouldnt it be better to use a wider f stop? Diffraction!
>
>I agree that diffraction becomes more of an issue with aberrations for some
>lenses beyond f 16.  I guess Leica in their optical wisdom felt the 28mm
>Elmarit's optical design could hold up to f 22 without a major loss of
>resolution or contrast.
>
>Another interesting observation I have made with the 28mm Elmarit is that
>the diaphram blades do not open all the way even though the lens is set for
>f 2.8.  Its almost as if Leica could have perhaps made this lens an f 2.0
>but felt the aberrations wide open wouldn't meet their strict criteria for
>sharpness or contrast levels.
>
>I am very pleased with the 28mm Elmarit.  For those of you who waer
>glasses, the external finder is very handy.  I use it like a point and
>shoot camera.  Very fast, very discreet.
>
>Happy shooting,
>
>Richard
>--------------------------
>Richard Clompus, OD
>West Chester, Pennsylvania, USA
>