Sami Ruusunen wrote:
I\'ve always thought this is caused by non flat film plane.
Non-flat as in curved? Don\'t all small format cameras have a perfectly flat pressure plate (and the Contax RTS even a vacuum system to ensure that the film is pressed against it)?
\"The diffusion effects of film combined with the Lorentian diffusion (normal types of reversal or negative film types that is, not archival density microfilm) can keep an MTF-50 up to 30lp/mm in red and maybe 70lp/mm in blue.
Normal MTF50 for the green layer in reversal film is 45-50lp/mm. This gives a 3600x2400 resolution frame on a 36x24mm negative - about the same resolution capability as a 9MP digital camera. Kodak and Fuji have film datasheets at their sites, even today.
But the important part is that film both diffuses resolution and compresses DR a lot, and that it diffuses differently in red and blue. Film behaves like if you took the red channel in a digital capture and ran a few pixel radiuses of Gaussian blur on it (without touching the others).
Add this to the fact that the three (sometimes more) layers of emulsion add up to a thickness of 60-90µm (less in some T-grain films, more in quite a few other types), and that the output DR is seriously constricted, and you have contained/minimized the problem.\"
Jan 11, 2012 at 02:03 PM
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