These images have an ugly checkered pattern in the darker areas. It lies on a strict pattern, which indicates it's probably a printing artifact and not a deliberate part of the image, so we should try to remove it. Turning GREYCstoration up to remove this will smear edges (-alpha 2.5):



(2x zoom. Levels adjusted in #3 for easier visibility.)

Rather than raising Greyc, NeatImage was used to reduce the checkering, and then the image was processed normally with GREYCstoration.



#1: Raw image.
#2: After NeatImage. High and low Noise Reduction Amounts are set to zero, so it only affects the middle-frequency noise of the pattern we want to remove; this was found by experimentation. Sharpening is off.
#3: Finally, a single GREYCstoration pass to remove the actual screening (-p 0.8 -a 0.5 -alpha 1 -sigma 1 -gauss 0.8 -fast -alt).
#4: For comparison, GREYCstoration at the same settings without first running NeatImage.

Updated by petopeto about 15 years ago