usher99@xxxxxxx wrote:
> Oh,
> I found the site that piqued my interest in the deconvolution
> routine.(R-L iteration).
>
> http://www.clarkvision.com/imagedetail/image-restoration1/index.html
>
The R-L processing is interesting and, in the example, clearly a bit
better than USM. But lets get right down to it. Anyone interested in
this stuff, I'd appreciate your votes on the alternates here.
<http://www.moosemystic.net/Gallery/tech/ARL_Sharp/Fox.htm>
Problems I see with his presentation and examples, which also mostly
explain the above:
- He refers to an end use of a print, yet never shows scans of prints
nor comments on any visible differences in actual prints of various
sizes. He doesn't seem to know about, at least doesn't mention, the
different sharpening needs for web display vs. printing. Images
optimized for printed output will generally look over sharpened, even
'crunchy' when viewed on screen.
- He does not compare it to more sophisticated approaches to sharpening.
The techniques in Bruce Fraser's book "Image Sharpening", Fred Miranda's
sharpening plug-ins and undoubtedly numerous others offer different and
often more effective sharpening than simple uses of USM - and without
the extreme processing overhead penalty.
- He only tries one up-sampling option. There are better tools
available. Qimage and other, more expensive and often specialized RIPs,
may use both more sophisticated up-sampling algorithms and different
sharpening algorithms, both optimized for printing, rather than viewing.
Based on what I see in his examples, it appears that the R-L processing
makes full pixel and upsampled images look better on screen than does
simple USM. My rough guess is that in a print of his side by side
example at his specified magnification, the USM version will look
better, sharper, clearer, than the R-L version at any normal viewing
distance.
For the screen? I think I've equaled or bettered his AR-L result using
far less exotic and processor intensive tools. I would not use any of
them for printing.
Moose
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