P. S. Moose writes:
>Mike G and others have pointed out that in theory, DC should not work
for
>correcting diffraction blur. In practice, with
>my lenses and images, it increases detail visibility and 'sharpness'
in images
>as apertures small enough that folks like
>Chuck say they are diffraction limited.
No, no. Chagrined Mike made a 140 deg turn in a rather long Feb post.
http://lists.tako.de/html/Olympus-OM/2013-05/msg02068.html
Yes, empirically R-L deconvolution can improve diffraction softened
images. However, there is a rather hard high freq cut off with
diffraction unlike
a Gaussian blur where high freq info leaks into the image. Why DC
still works is well, convoluted--- but detail contrast is improved even
if no/little actual resolution derived.
My current conjecture is DXO uses non PSF deconvolution but applied
in a weighted fashion in the image where the lens is most affected by
aberrations--at least
as far as that one function. That opinion is based on a few
correspondences with their tech support a number of years ago--they
keep their cards
very close to their chest now. I have read that Canyon with DLO
actually mathematically models the lenses including diffraction
effects and the AA filter.
I agree with Moose that lightly applied deconvolution is less
manipulative than USM as it is recovering data contained within the
image.
Perhaps not always quite sharp enough, Mike
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|