FZ200 Diffraction Limit - Panasonic Tech Service

Started Aug 27, 2013 | Discussions thread
Stephen Barrett Contributing Member • Posts: 683
Re: FZ200 Maximum Desirable F-Number to achieve adequate "Sharpness"

This is a most interesting thread!
Thank you, J C Brown and Ianperegian for all the testing you have done. I had not thought about all the complications of various colour combinations and did not know about "crosstalk".

The discussion of how many pixels are required per line-pair is also very interesting (J C Brown, sherman_levine & Detail Man).

If I may summarize some of the suggestions:

  1. In his paper, J C Brown has proposed 3 pixels per line-pair, also citing Helmhotz' use of this criterion. (I am a big fan of Helmholtz's book "On the Sensations of Tone".)
  2. sherman_levine has suggested 2 pixels per line-pair.
    This is what I used in my crude calculations of (lens + sensor) resolution. My reason for using 2 was that full extinction of the pattern would be rare, occurring only with a precise alignment of the camera with the target. This "sensor resolution" of 2 pixel-widths was then combined with the lens resolution (~9% MTF) by taking the square root of the sum of the squares. The results seem to match my test results surprisingly well for my Canon SX30. This thread is making me wonder how that is possible.
  3. Detail Man says that "it seems a wonder" that 3 photosites per line-pair are enough. If I understand his argument, 2 per line-pair is not enough because of the distortions that result from aliasing and because of "filters" that the camera uses in processing. My impression is that the rest of us are thinking predominantly in the space domain, whereas Detail Man's descriptions are mostly in the frequency domain, using MTFs, which is a fundamentally more powerful way of analysing the combination of all the complicated systems in a camera.
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