Leica Rumors: M10 to be BW Camera

Started Mar 20, 2012 | Discussions thread
Oldboy 1948
Regular MemberPosts: 226
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Re: 50% MTF resolves without needing 1000:1 target contrast
In reply to BJL, Mar 20, 2012

BJL wrote:

Oldboy 1948 wrote:

BJL wrote:

18MP would not come close to making full use of the resolution that Leica lenses can deliver. For one thing, it still does not match the sharpness and detail given by fine grained B&W films like TMAX-100: 125lp/mm at a healthy 50% MTF
Reference on TMAX-100:
http://www.kodak.com/global/en/professional/support/techPubs/f4016/f4016.pdf

You need a contrast of 1:1000 to get 125lp/mm but at 1:1.6 it is only 40.

Where do you get those numbers from? 50% MTF is a well accepted measure of highly useful resolution, avoiding exaggerated film resolution claims based on extremely low MTF visible only with extreme high contrast targets. You surely do not need a target with 1000:1 to resolve at 50% MTF: the image would still have 500:1 contrast, far more than a print can show.

It might be that the MTF measurements are done with a 1000:1 target, but that does not mean that the details can only be seen with such high contrast in the subject.

P. S. The figure of 125 lp/mm @ 50% MTF is from the graph on page 14 of the Kodak reference sheet that I linked to: cycles per mm is the same as line pairs per mm.

Aside: thanks to adjacency effects, MTF for TMAX-100 stays at or above 100% till 50 cycles/mm; even that is beyond the 40 you mention.
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Smaller lenses, better in low light, more telephoto reach:
you can have any two at one time.

Page 25. Resolving power

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