Archived posting to the Leica Users Group, 2001/11/06
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]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 - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html