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

Started Jan 4, 2014 | Questions thread
Reilly Diefenbach
Reilly Diefenbach Forum Pro • Posts: 12,156
Re: 50mm Prime with Resolution for a D800? Come on Nikon/Sigma!

Scott McMorrow wrote:

Actually, you are wrong. 3200 lw/ph for a D800 computes to approximately 15 Mpix.

No.  Take any decent 50 and start counting actual pixels from side to side.  They'll all be there.


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.

Uh, this was taken by the Sigma 70 in residence at Imaging Resource, their sharpest lens.  This is as good as it gets.

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.

Any 50mm, 60G, 24-85VR at center, all produce the exact same stuff when zoomed in, as I have verified a thousand times.  I would defy you or anyone else to come up with pixel level crops from 50mm lenses at f8 that look any better from one to the next, regardless of the technobabble.  Have at it, Scott.  You're obviously on a mission.  Let's see what you've got!  No charts, please, just pics.

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