Re: [Leica] DR Summicron MTF (was: For your information)

[Seth Rosner <sethrosner@direcway.com>]

Akhil wrote:

> The reason I asked about chromatic abberations is because I have several
DR's S/Ns ranging from 1,7xx,xxx to 2,2xx,xxx and also examples of the later
50mm Summicrons; not one of the DR's gives me the "snap" of the later
lenses, yet your data seems to indicate comparable MTFs. I am trying to
figure out why.

Chromatic is only one of the aberrations that degrade images. As Erwin Puts
has correctly stated, different lenses have what he calls different
"fingerprints". What fingrprint pleases you, says Erwin, is a matter of
taste. Again, he's right. As to your DR Summicrons, at what apertures are
you shooting? The contrast of the DR at f/2 does not match the current lens,
as I have written. So if you shoot mainly wide open, your negs and slides
will not have quite the "snap" of the current 50. DR contrast gets closer at
f/2,8 and is very close indeed at f/4, 5,6 and 8; in fact at these
apertures, DR contrast at some points on the film plane exceeds that of the
current 50. So in comparing lenses, one has always has to ask what am I
looking for at each of the parameters.

Also remember that "sharpness" is not a objective, quantifiable value as are
contrast and resolution. Sharpness is the impression the human eye gets from
perceiving an image. A high contrast, medium resolution image is going to
appear "sharper" than a medium contrast, high resolution image. Because at
any level of frequency, 5, 10, 20, 40 or more line pairs/mm, sharper
definition of the edge of the image (greater contrast) will enhance the
impression of sharpness.

As you have read from other LUGGERS, there are those who really like the
singular quality of the images that the DR/Rigid produces. And if they do
not need f/2 most of the time, it is the lens they will use most of the
time.

I hope this ain't gobbledegook.

Seth            LaK 9

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