Archived posting to the Leica Users Group, 1998/05/02

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Subject: Re: [Leica] Lens Formulas and Depth of Field (35mm Summicron formulas)
From: Alfred Breull <puma@hannover.sgh-net.de>
Date: Sat, 2 May 1998 21:30:57 +0200

At 17:51 02.05.1998 +0200, Erwin Puts wrote:
>     ...It is difficult to imagine. I will try a picture next time. But
>the bigger shape of the unsharpness blur (or patch of light in the image
>plane) in the case of the ASPH gives the more pronounced unsharpness idea.
>It is a matter of the greater sharpness of the in focus object points of
>the ASPH.

Thanks, Erwin. That explains and also underlines our observations.

Evidently the effect is more pronounced in high speed lenses, i.e.
asph 1.4/35 Summilux, than in "normal" speed lenses, i.e. 2/35 asph
Summicron.

In general, I think, there is no problem to say in future, that 
the relation between sharpness and unsharpness in asph high speed
wide angles is too strong for wide angles. It's not so far away 
from previous comments, which state, that the unsharpness is too 
sudden or too abrupt.

The increase in sharpness is fine for anyone who uses wide angles 
and still wants to get the subject clear of the background. But, 
also as a consequence, the 3D impression, which Leica lenses have 
been famous of, is - maybe not totally lost, but - definitely 
reduced.

Alf



- --------------------------------------------------

Alfred Breull
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