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I recommend posting a raw image and the same scanned image to the site, and linking them from here. This way, people can easily see "before/after".

midzki said:
1. adjust only color levels manually (not use auto levels) while a scanner shows a preview, and make other filters all turnd off.
Levelling by hand can be very difficult. Using an IT8.7/2 target (such as from http://www.targets.coloraid.de, R1, $20 shipped) can do this accurately, giving exact colors instead of having to do it by eye. (If you have a good eye, it might not be necessary, but it's cheap and also eliminates errors due to monitor error.)

2. scan all with 600dpi.
3. if scans have moire, resize them into 300~450dpi.
If you have moire at 600 DPI, resizing down is going to blur the screening away (poorly) and may make it harder to get good greycstoration output. I'd try leaving it at 600 DPI and increasing alpha in greycstoration a bit, maybe...

(The real fix is to scan at a higher DPI, but that can be very slow.)

4. apply Greycstortion twice with different settings.
1st setting is p=0.7~0.8, a=0.2, α=1.0~1.5, σ=5.0
2nd setting is p=0.4~0.6, a=0.4~0.6, α=0, σ=2.5
(this settings may give you overfiltered images)
Greyc settings used at 600 DPI will blur the image more at 300 DPI. You may want to lower alpha a bit for 300 or 450 DPI compared to 600 DPI.

70->See if there are portions where I want detail over low noise, load the mid-product saved in 20 and replace them.
For images I'm giving more attention to, I sometimes do this:

- load into Photoshop (this is where I do all my greyc work anyway)
- duplicate the layer (control J)
- select the top layer, and run Greyc normally
- select the bottom layer, and run Greyc with lower settings appropriate to the smaller, detailed parts of the image (blush lines are a very common problem)
- select eraser tool, set a low hardness (~25%), and erase from the top layer where I want finer detail