Archived posting to the Leica Users Group, 1998/05/01

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Subject: Re: [Leica] Leica lenses stopped down below 5.6
From: Chris Bitmead <chrisb@ans.com.au>
Date: Sat, 02 May 1998 06:47:49 +0000
 
LRZeitlin wrote:
> 
> Hard as it is to believe, a theoretically perfect lens is at its sharpest wide
> open. The reasons are hard to explain but if you really must know why, consult
> a good textbook on photographic optics.

Well, surely a "perfect" lens would be perfectly sharp at all
apertures. :-)

Some really expensive telephotos have been tested at the exactly
the same performance (very good on the Chasseurs tests) between
wide open at f1.8 and closed down to f5.6.