Archived posting to the Leica Users Group, 1998/11/19

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Subject: [Leica] MTF explanation
From: Carsten Bockermann <Carsten_Bockermann@compuserve.com>
Date: Fri, 20 Nov 1998 01:56:25 -0500

Nathan,

>>but I still cannot see how a film can produce more detail than in
>>the original scene. 

looks I donīt explain very well. Another try : we are not about 'more
detail' here, but about 'more contrast' (i.e. a bigger difference in
luminance/light transmission). The y-axis of the MTF graph denotes how much
of the contrast between the white and the black lines of the resolution
target is reproduced on the film. So 50% means that the contrast on film
would be half of the original contrast.
A value above 100% can be achieved by contrasty films. The best example is
a special kind of repro film (donīt know the correct English word, in
German itīs called 'Strichfilm') that is either black or white but never
grey. This is simply achieved by the film exaggerating whatever contrast
there is.

Hope this helps

Carsten

http://ourworld.compuserve.com/homepages/Carsten_Bockermann/