[Leica] DR contrast

[benedenia at gmail.com (Marty Deveney)]

Are Leica's MTFs measured like Zeiss published or calculated, like
almost every other manufacturer.  The latter is a good way to
introduce a lot of bias into your data.

Just interested.

Note that the 50/1.4 ASPH is not limited by spherical aberrations and
has much higher contrast and resolution than the DR at f2.

Marty

On Fri, Sep 24, 2010 at 5:06 AM, 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
>
>
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