[Leica] DR contrast

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

Good point Phill, most older lenses have fog which is not obvious 
unless you use a penlight.  I've often sat in the dark looking at all 
me lenses and was a bit troubled when I realized they all were foggy 
compared a new 50 Summicron right out of the box.  That's when I 
started up my relationship with Sherry and now routinely send my 
lenses to be cla'd about every two years to keep the fog level to a 
minimum.   Subsequently I've learned about many other things that go 
wrong with these lenses.

At 03:47 PM 9/23/2010, you wrote:
>I love my DR and my Rigid Chrome Summicrons. The DR is the lens I will
>own if all the others were to have to go away.
>
>I think much of the "softness" lore these days may have to do with the
>state of the particular sample of lens itself. Many have some very
>significant coating marks and fogging is not uncommon either.
>
>I agree though, that the lenses perform fantastically. On the M8 they
>are incredible.
>
>Phil Forrest
>
>
>On Thu, 23 Sep 2010 15:36:05 -0400
>"Seth Rosner" <sethrosner at nycap.rr.com> 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
>
>
>_______________________________________________
>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