Quote Originally Posted by timparkin View Post
The results for diffraction limit is variable depending on whether you use points or lines and a figure of 1/100 for f/22 isn't impossible.
Thank you for your reply. What do you exactly mean with "1/100"? 100 lpm or 50 lpm? If you think of 100 lpm, Iīm interested, where do you cite this value from?

For monochrome light with a wavelength of 486 nm (blue, the wavelength most lenses are first of all corrected for) and for a working distance of 100 times the focal length I find a diffraction limit of 75 lpm (f/22) in my photographic chart book (Wunderlich: Tabellenbuch Fotografie, 1984). 486 is somewhere in the the middle of TMax 100īs spectral sensibility response. If Perez / Thalmann used flash or daylight then the diffraction limit at 486 nm could be good value to calculate with. Since they used a working distance of 20 times the focal length if I got them right, the diffraction limit is lower than 75 lpm. From my chart book the diffraction limit drops from 75 at 100 times to 68 at 10 times the focal length working distance. Perez / Thalmannīs working distance (20 times) is in between 100 times and 10 times, where one could use a diffraction limit of roughly interpolated 72 lpm as a value to calculate with. The resulting systemīs resolution would be 53 lpm.

I know all of this is very theoretical, but Iīm interested how realistic the Perez / Thalmann findings are in absolute terms. This is especially interesting when you want to compare their values with other lpm values for instance for MF or 35mm lenses.

Quote Originally Posted by timparkin View Post
However, you should read that at the bottom they say that the survey is intended as a 'relative' comparison of the lenses on test..
Iīm aware of that, but in their comments they try to compare lpm values of LF lenses with lpm values of MF and 35 mm values that they achieved in own testings or did find in publications.

Donīt get me wrong - I appreciate the broad resolution testings, Perez / Thalmann did, very much. Just want to know how sensible it is to compare their lpm values to others that were publicized and compare the results of my own (very small) testings.



Another interesting question regarding this issue: Who also has tested the lpm resolution of LF lenses? Did you find similar values and how did you do your testing?