The 180mm Shoot-out
/forum/topic/1181458/4

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theSuede
Registered: Jul 31, 2008
Total Posts: 2221
Country: Sweden

alundeb wrote:
I think it is in how we map the Rayleigh criterion into lines or line pairs.

When two airy disks intersect as the Rayleigh criterion, the maiximum of one coincides with the first null of the second. The distance between the maxima is then equal to the radius of the airy disc. The point is, these two maxima represent a line pair when they represent two bright lines with a dark line between them. So the Rayleigh criterion maps directly into line pairs per mm, not lines per mm.

Edit:

Yes, that is how it is.

Rayleigh for green at F2.95 is 500 lp/mm not 250 lp/mm.

Scroll down to diffraction:

http://www.normankoren.com/Tutorials/MTF1A.html


Of course. My error, and THAT'S why you shouldn't write stuff like this when getting home at three o'clock in the morning while still slightly drunk. A factor fo two it is, Rayleigh = lp
*hangs head in shame*



macrobild
Registered: Dec 20, 2012
Total Posts: 128
Country: Sweden

well , typical Swedes and Finnish people, they are always drunk at 0300 by factor 2 .
but we walk slowly toward the light again, and the mid night sun



Lee Saxon
Registered: Jun 07, 2012
Total Posts: 755
Country: United States

I've posted Want To Buy ads here for lenses still needed in the comparison.



Lee Saxon
Registered: Jun 07, 2012
Total Posts: 755
Country: United States

philip_pj wrote:
Lee, I would not be too fussed on the multiple sample front, if your aim is not purely a 'sharpness' derby. Though admittedly the thread is bending off in that general direction. I am much more interested in the overall perceivable photographic quality of images of the sort that regular photographers take, which looks to place me in the small niche of photographers down at the end of the distribution.


I'm definitely with you on real world testing and visual examples. There will be a mixture of normal field shooting and deliberate, Lloyd-Chambers-esque A-B comparisons. I'm just going to do an Imatest "sharpness derby" also

The multiple samples aren't really about maximizing the "sharpness derby" results, though. Roger Cicala's blogs make it clear 2-3 samples isn't nearly enough for that. It's more about screening for actual bad samples. For example, the Zeiss Jena 180/2.8 is supposedly the same optical design as the very first 180mm from 1936. My expectations for that lens aren't very high; I could get a bad sample and not realize it.



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