03-25-2012, 09:23 PM
[quote name='Klaus' timestamp='1332608815' post='17001']
...
However, if I applied more aggressive settings to the conversion profiles there would have been a danger to land beyond Nyquist at times and, frankly, I'm tired of that discussion.
[/quote]
Why not? We haven't had that for a long time. I really miss it <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/tongue.gif' class='bbc_emoticon' alt='
' />
You might remember the paper I found recently and shared here in the user forum: oatao.univ-toulouse.fr/303/1/estribeau_303.pdf If you look at figure 6 and the texts around it, it explains nicely the ideas behind the "slanted edge" method for measuring MTF. If you look at the figure it explains how you get a better sampling of the edge than the sensor pixel pitch would suggest. One is not violating Nyquist's theorem here at all - by combining the results from several lines, you use a higher sampling frequency than the pixel pitch, that is all. Anyway all Bayer sensors (try to) do that anyway. The pixel pitch of the green sites is by sqrt(2) larger than commonly quoted.
If one looks at oatao.univ-toulouse.fr/297/1/estribeau_297.pdf by the same authors, figure 16 shows examples of how strong a signal beyond Nyquist can be obtained with "slanted edge" methods.
Figure 16 of the second paper also shows, when using a proper calibrated slanted edge method, on can obtain results that are essentially compatible to traditional sine-pattern methods. For sure your results will not be, since the cameras you use as a sensor are not calibrated. You know and say that every time this topic come up.
All in all this is quite interesting and new to me. Once one understands it, it is just so obvious what is going on here <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' />
Have a good evening.
Joachim
...
However, if I applied more aggressive settings to the conversion profiles there would have been a danger to land beyond Nyquist at times and, frankly, I'm tired of that discussion.
[/quote]
Why not? We haven't had that for a long time. I really miss it <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/tongue.gif' class='bbc_emoticon' alt='
' /> You might remember the paper I found recently and shared here in the user forum: oatao.univ-toulouse.fr/303/1/estribeau_303.pdf If you look at figure 6 and the texts around it, it explains nicely the ideas behind the "slanted edge" method for measuring MTF. If you look at the figure it explains how you get a better sampling of the edge than the sensor pixel pitch would suggest. One is not violating Nyquist's theorem here at all - by combining the results from several lines, you use a higher sampling frequency than the pixel pitch, that is all. Anyway all Bayer sensors (try to) do that anyway. The pixel pitch of the green sites is by sqrt(2) larger than commonly quoted.
If one looks at oatao.univ-toulouse.fr/297/1/estribeau_297.pdf by the same authors, figure 16 shows examples of how strong a signal beyond Nyquist can be obtained with "slanted edge" methods.
Figure 16 of the second paper also shows, when using a proper calibrated slanted edge method, on can obtain results that are essentially compatible to traditional sine-pattern methods. For sure your results will not be, since the cameras you use as a sensor are not calibrated. You know and say that every time this topic come up.
All in all this is quite interesting and new to me. Once one understands it, it is just so obvious what is going on here <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' />Have a good evening.
Joachim
enjoy