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petopeto said:
Are you sure they weren't both -a 0.6? 1.0 tends to cause swirly artifacts, but I don't see that.
Interesting?
I set parameters extremely to show how -a & -sigma works.

[edited]

let's me try more sophisticated way with the old scan.
post #56929
1) gaussian blur: 2px
2) greycstoration: -dt 10 -p 0.2 -a 0.6 -alpha 3.0 -sigma 0
3) greycstoration: -dt 20 -p 0.2 -a 0.7 -alpha 1.0 -sigma 3.0
4) high pass sharpen: gauss 5px opacity 60%