[Leica] DR contrast

[chs2018 at med.cornell.edu (Chris Saganich)]

Thanks Seth, that confirms what I seem to have been seeing as the 
major difference between my DR (your former DR btw) and the later 
50's I have.  The later 50''s worked very well for long exposure work 
where I exposed up to 45 seconds at f2.  Here is one example:

http://www.imagebrooklyn.com/Portfolio/Williamsburg%20Portfolio/Williamsburg%20page%201.htm

As you mentioned when I used the DR for this sort of work the 
difference was obvious.

At 03:36 PM 9/23/2010, you wrote:
>Scanning the batched conversations I came across this one that caught my eye
>and about which I have some significant knowledge. Some on the list may
>recall my writings in LHSA's Viewfinder magazine several years ago
>contradicting Erwin Puts' statements about the series of 50/2 Summicrons.
>One of them even resulted in marc small accusing me of libel and predicting
>that Erwin would sue me. Poor lawyering on marc's part as truth is an
>absolute defense to a defamation action.  ;-)
>
>
>
>My purpose here is to dispel a very widely held opinion that the 1956
>DR/Rigid 50 Summicron is a low-contrast lens. It is not, except when
>compared to the latest Leica and other lenses at wider apertures. Ten years
>ago I had correspondence with Lothar Koelsch, then head of lens design at
>Leica, about this very issue and received from him print-outs that I have in
>my hands as I write, of the MTF curves calculated by Leitz/Leica Camera, for
>the 50/2 lenses from the Summitar through the DR/Rigid, 11817 (1969) and the
>1979 version that I believe is still current.
>
>
>
>Bear in mind that every lens is a compromise, that there is no such thing as
>a perfect lens. If there were, such a lens would perform flawlessly at full
>aperture and as a photographer stopped down, the image would degrade
>progressively because of diffraction! So the designer has to decide in which
>direction he/she wishes to correct for most, since one cannot correct all
>aberrations simultaneously. The DR/Rigid concedes some softening contrast at
>f/2 and 2,8 in order to correct more highly for spherical and chromatic
>aberrations and thus achieve significantly higher resolution. Geoffrey
>Crawley, then Editor-in-chief of the British Journal of Photography,
>confirmed to me in our correspondence in the late 1960's, that due in some
>significant part to the emphasis put upon contrast by the great Japanese
>manufacturers, principally Nikon and Canon, that seemed to have persuaded a
>large number of photojournalists to favor highest possible contrast (keep in
>mind that most of these folks did then and still do tend to shoot wide open
>most often, eh Tina & Ted?), Leitz designed the 1969 50 Summicron #11817,
>for max performance at f/2. And wide open, looking at the MTF charts, no
>question the contrast of 11817, especially at the lower spatial frequencies
>- 5, 10 & 20 line pairs/mm is significantly better than the DR. At f/2,8 it
>is better than the DR but only on axis; at the near and far edges the DR's
>contrast is superior and at f/4 and 5,6 it is markedly superior, again
>except directly on axis. As to the current 50 Summicron, contrast is
>somewhat superior at the first three stops whilst the resolution of the DR
>at medium apertures is better than both later Summicrons.
>
>
>
> >From Leica's own  MTF charts it is clear that the myth of the DR/Rigid 
> >lens
>being soft and low-contrast is just that - a myth. Use that lens at f/5,6 &
>f/8 and even at f/4, and you have an extraordinary image-maker. And using a
>rigid 50 on an M8 as I do is even better, since it eliminates the outside
>quarter of the image circle wherein lies the vast majority of the design's
>"softness".
>
>
>
>Just my 2c.
>
>
>
>Seth
>
>
>_______________________________________________
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Chris Saganich MS, CPH
Senior Physicist, Office of Health Physics
Weill Medical College of Cornell University
New York Presbyterian Hospital
chs2018 at med.cornell.edu
http://intranet.med.cornell.edu/research/health_phys/
Ph. 212.746.6964
Fax. 212.746.4800
Office A-0049