50mm Prime with Resolution for a D800? Come on Nikon/Sigma!

Started Jan 4, 2014 | Questions thread
Scott McMorrow
Regular MemberPosts: 362
Re: 50mm Prime with Resolution for a D800? Come on Nikon/Sigma!
In reply to Reilly Diefenbach, Jan 5, 2014

Actually, you are wrong.  3200 lw/ph for a D800 computes to approximately 15 Mpix.  Your "test" does not show black lines that are separated at the pixel pitch.  In fact, you can already see at the edges that pixels are blurring into the neighboring white space.  Place another black region one more pixel over, with only one pixel of white space, and you will see the "resolution" collapse, because of poor microcontrast due to blur radius.

This is why resolution measurements are made with a specific contrast level specified.  MTF50 being a common standard, since it seems to track well with the way our visual systems perceive detail. Without specifying the contrast metric that is being used, a resolution measurement is meaningless.  This is akin to measuring bandwidth in analog electrical systems.  A measurement amplitude must be used or the bandwidth measurement is meaningless.  For electronics 3 dB (70.7%) amplitude or 6 dB(50%) amplitude is often used.

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