03-11-2011, 07:30 AM
[quote name='genotypewriter' timestamp='1299800615' post='6660']
Klaus, how do you determine the USM radius?
GTW
[/quote]
There's no hard rule. Upon a start of a new test system we're analyzing the USM effect (with different parameters) on the center portion of an image taken at the sweet spot of a lens. Usually we stick to a smaller than average USM radius in order to avoid an unreasonable boost of the usually much weaker border/corner region.
Technically we're probably using too weak USMs. There're many lenses which are outperforming an AA-less sensor in the image center after all. However, it is, of course, reasonabe to stay below the max. resolution of a sensor after USM and I do actually refuse to sharpen aggressively (remember then Pentax K-5 discussions about this). While imatest can look a bit beyond Nyquist due to being able of making assumptions about the test target (an assumption-less Nyquist can't look beyond the barrier, of course) I don't really think that this is overly reliable anymore.
Klaus, how do you determine the USM radius?
GTW
[/quote]
There's no hard rule. Upon a start of a new test system we're analyzing the USM effect (with different parameters) on the center portion of an image taken at the sweet spot of a lens. Usually we stick to a smaller than average USM radius in order to avoid an unreasonable boost of the usually much weaker border/corner region.
Technically we're probably using too weak USMs. There're many lenses which are outperforming an AA-less sensor in the image center after all. However, it is, of course, reasonabe to stay below the max. resolution of a sensor after USM and I do actually refuse to sharpen aggressively (remember then Pentax K-5 discussions about this). While imatest can look a bit beyond Nyquist due to being able of making assumptions about the test target (an assumption-less Nyquist can't look beyond the barrier, of course) I don't really think that this is overly reliable anymore.