[Leica] DR contrast

[photo.forrest at earthlink.net (Phil)]

Any information out there about the rare-earth Summicrons? 

If I recall correctly, they were all made in collapsible mounts but if
there was a rigid version ever made, I'd love to find one.

Alternatively, I could have a collapsible collimated to a digital
sensor and "locked" in the out position somehow to ensure that it kept
its proper registration. 

I only mention the rare-earth lens because one of my favorites is the
SMC Takumar 50mm f/1.4 with rare earth elements. It's fantastic when
not fogged. That lens is the reason that I always want to keep a
Spotmatic around. 

I've pondered long and hard on how to get that lens properly focusing
on a Leica, be it with transfer of the optical cells or an adapter with
RF coupling.

Phil Forrest


On Fri, 24 Sep 2010 11:01:57 -0400
Chris Saganich <chs2018 at med.cornell.edu> wrote:

> 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
> >
> >
> >_______________________________________________
> >Leica Users Group.
> >See http://leica-users.org/mailman/listinfo/lug for more information
> 
> 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
> 
> _______________________________________________
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