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Message: <blockquote data-quote="Surveyor" data-source="post: 3174698" data-attributes="member: 50720">DavidI tried to access the actual data file but could not find it quickly so did not search too long.I believe the plot is correct. This was done 6/2007 and made a lot of changes since then but notice the diffraction limited line crossing the right border at 40% contrast. On a perfect MTF 40% occurs about half way along the x axis so this would extend to 60 c/d and 7" would be about 64 c/d.The biggest problem I had with that software program was that it would only generate a max of 2x Nyquist which was very limiting for poor optics and it showed the first 5% contrast point it came across where the sample pixels would cross the 5% contrast limit many times.While the plot would scale to cyc/deg the actual data dump to a csv file was in cyc/pixel so I had to do the actual plots at that time in Excel to do the conversion to extend past 2x Nyquist. Also the target was not a standard picture so picture height did not apply. The target in those days had an ROI of about 30x100 pixels so picture height varied.Extended out the plot would look a lot like those for the 2 wave SA or 2 wave astigmatism in the response to Kimmo above.I am mostly going from memory here and if I find any difference when I get a new CPU fan I will get back to you.PS: On that camera 1 pixel is about 10"/8X or 1.25".</blockquote>