Archived posting to the Leica Users Group, 1998/09/26

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Subject: [Leica] Strong statements, but true?
From: Erwin Puts <>
Date: Sat, 26 Sep 1998 19:47:29 +0200

On Zeiss lenses it has been noted:
>What was of interest were the following statements in a
>handout describing the gear involved: 1.) " One hundred
>twenty to 130 lppm is necessary to make a high quality 16
>X 20 print". 2.) Describing their Planar 50 f1.4, set at f8;
>"This is the highest resolution ( 200 lppm across the entire
>field ) lens available in the world for general photography".

>Questions are as follows: 1.) What Leica lenses would meet
>the 120-130 lppm criteria? 2.) How does the new R-50 f1.4
>compare to the Zeiss 50 f1.4?  3.) Does the RTSIII  vacuum
>back ( flatter film )enhance the sharpness of a lens significantly?

I would venture to comment as follows:
The pictures are made by Mr Fleischer whom I met a few times and talked
extensively about image quality (seems to be my predestination). In his way
of analysing "lppm"is not what you would expect linepairs per millimeter
but lines per millimeter. So when on these occasions Zeiss speaks about 200
lppm, they are talking about 200 lines/mm or 100 linepairs/mm in
Now the statements:
a high quality 16x20 print needs 60 to 65 lp/mm (converted to standard
parlance). It depends: if looked at minimum distance (25cm from eye to
print) for some kinds of objects this figure is needed. At normal viewing
distances high quality is possible at 10 linepairs/mm.
The Planar at f/8 is the highest resolution lens available. Misleading: it
is very doubtfull if the Planar can resolve details at 100 linepairs/mm
(again converted figure) at f/8. Across the entire field is impossible.
Look at any MTF Graph from Zeiss and note the diverging sagital and
tangential lines in the outer zones.
More important than the maximum figure (100 or 110 or 90) is the contrast.
I am sure at this figure (100 lp/mm) the contrast is below 10% and
therefore not relevant. Most Leica lenses can resolve 100 lp/mm in the
center at f/8, but contrast is so low as to make the details wash out.
The questions then: most modern Leica lens meets the 60 to 65 lp/mm
criterium in the center and across part of the field.
The new R-50/1,4 is better than the Zeiss Planar 1,4.
The vacuum back does hardly improve the image quality as the film curvature
is within the circle of confusion tolerance even at f/1,4.

And a comment was:

>PS : The test made by Zeiss is stupid. A 1.4/50 lens has been designed to
>be used at full aperture and not at f8.

I always wonder why this statement is reserved for a f/1,4 design and is
not being made for a f/2,0 lens. Any f/2,0 lens is expected to perform well
at full aperture and stopped down. The same expectation is valid for any
modern f/1,4 design. As I explained earlier any f/1,4 design will have
uncorrected aberrations to a higher degree than a f/2,0. Still modern
design has advanced quite significantly the last 20 years to such a degree
that a good f/1,4 can be favourably compared to a good f/2,0. On holiday I
shot comparison pictures with the new Summilux-R 1,4/50 and the Summicron-M
2/50 at all apertures and noted no significant differences (on the bench it
is another matter: in itself an interesting observation!).
The statement in the olden days that a 1,4 is designed for full aperture
and not stopped down, is plainly a weak excuse for saying that the lens is
not good at all apertures. It is true that the former Summilux-R 1,4/50 did
not improve to the very high level of image quality Leica nowadays demands
from every lens when stopping down (the reason BTW for its redesign). But
in general any modern 1,4 is designed to have excellent image quality when
stopped doen. The Zeiss test then is fully justified