Hi John,
here the answer from Dr. Nasse from Zeiss:
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True Biogon lens types have a very short distance between the last lens and the film plane. This is partly the reason for their extraordinary image quality with respect to sharpness and with respect to low distortion. Every mm increase of that distance makes it much more difficult for the optical designer to achieve the same quality level without increasing the optical efforts in terms of number of elements or aspherical lenses.
Because of that design principle the Biogon types have as well a very short distance between the exit pupil and the film plane. Therefore light beams going to the corner of the frame are inclined by about 45 degrees. Some present digital sensors will respond to such oblique ray incidence with some loss of sensitivity or a certain amount of cross-talk between the pixels.
Thus the combination of these lens types with some kinds of sensors, at least as long as the full format 24x36mm is used, could causee some trouble. But since the technology of sensors is developing very fast, it might be possible, that the restriction of digital application of the Biogon is not forever...
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This sounds very good I think and gives room for speculations for a digital G-body. Let's assume that sensor technology is develping as fast as in the past, we might even be able to use full-size chips on G or C/Y bodies...
If we look for ex&le at the new Kodak bodies, it seems to be possible to sue full-size chips with a smaller lens mount than the current N-system.
Let's see what happens at Photokina in September...