Archived posting to the Leica Users Group, 2001/11/06

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Subject: Vs: [Leica] digit stuff for those interested
From: "Raimo Korhonen" <raimo.korhonen@pp2.inet.fi>
Date: Tue, 6 Nov 2001 19:42:23 +0100

OK - now I understand a bit more. Thanks.
But it is not impossible to use Leica lenses on a digital camera.
All the best!
Raimo
Personal photography homepage at http://personal.inet.fi/private/raimo.korhonen

- -----Alkuperäinen viesti-----
Lähettäjä: Jim Brick <jim@brick.org>
Vastaanottaja: leica-users@mejac.palo-alto.ca.us <leica-users@mejac.palo-alto.ca.us>
Päivä: 06. marraskuuta 2001 17:58
Aihe: [Leica] digit stuff for those interested


>I was told, off line, the following:
>
>"Fact is, your bringing up digital 4x5 lenses, when talking about a Leica, is
>just ludicrous and you should know it."
>
>Since I wrote a response, I decided to share it with the group.
>
>The parallel is that the "film" 4x5 lenses are too sharp, their MTF is too 
>high for digital sensors, just like MTF of Leica lenses is too high for 
>digital sensors. So Schneider (and others) designed a set of lenses with a 
>MTF that is matched to digital sensor spacing. And wrote a white paper 
>explaining the facts and why they had to do this. Which is why Leica will 
>not mount an M lens on a digital camera. They have designed new lenses for 
>their partnered (Panasonic) cameras. The Canon and Nikon SLR lenses that 
>are used on their respective cameras are not redesigned, but the cameras 
>contain low-pass filters to "dumb down" the lenses before the image gets to 
>the sensor.
>
>The bottom line is that all lenses are equalized by digital sensors. A 
>leica lens is no better or worse than a Sony or Olympus or whatever lens. 
>The things we buy Leica lenses for are lost in the digits. In film, a 1 
>micron square silver halide grain contains 20 Billion silver halide 
>molecules, each capable of being hit (exposed) by a photon. It only 
>requires three being hit to produce a developable speck. A digital sensor 
>pixel (the minimum recording spot) is 5 microns square (25 sq. microns vs 1 
>sq micron) and will ultimately report a light level of 0-255 (256 levels) 
>for this whole vast area of 25 sq. microns. This is why Leica lenses out 
>perform most other lenses on film, but are no better than anything else on 
>pixels. And why film can record deep shadows and bright highlights in the 
>same scene. Digital sensors cannot. All fine detail (Leica's strong point) 
>is completely lost. Digital cameras are digital cameras. Their integration 
>into a film camera body by Canon, Nikon, Kodak, & Fuji is simply to give 
>professional photographers a known base to start from. The professional 
>level digital cameras from Olympus and others that don't look like 
>traditional SLR's and have non-interchangeable zoom lenses produce 
>photographs equal in every way to the SLR interchangeable lens cameras. 
>They just aren't "familiar" to the pro photographer.
>
>Astro photographers have the same problem. But instead of dumbing down the 
>lens, they shift the sensor half a pixel in four quadrants, take four 
>exposures, and then analyze the result with software to pick up points that 
>fall in between pixels and to differentiate double stars from single large 
>objects. A static CCD sensor cannot record these (and other) phenomenon. 
>And without either dumbing down the lens MTF or taking multiple exposures 
>and processing the results via software, serious aliasing occurs that is 
>not fixable with software without producing other artifacts. None of these 
>problems occur using film. But film has to be processed and scanned to get 
>the image into a computer for analysis.
>
>Basically, digital cameras are digital cameras. The digital sensor is the 
>great equalizer. All lens/camera brands sharing similar sensors and price 
>will perform equally. Only the post processing software can make a visual 
>difference. Lens performance is completely lost. And it will remain this 
>way as long as the 5 micron square pixel is the smallest obtainable.
>
>Jim
>


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