FFT (Fast Fourier Transformation) Photoshop plugin by Alex V. Chirokov

This is a very great freeware-plugin for photoshop. You can eliminate any form of regular patterns (e.g. removing the CMYK-raster from a scanned print).

It's hard to find the plugin on the net. And if you find it, you will likely have an old version, which have some problems with larger images.
I asked Alex Chirokov for a new version and he had a new version ready! (Thank you very much, Alex!)
It now works for images up to 4800x4800 pixels.

This page will save this great and free plugin for the future...

Original scan:

Applying the FFT filter:

Switch to green channel:

All white stars you can see are a representation of the regular CMYK-pattern. Cover all white stars with a black pen (except the center star!):

Now switch back to RGB and apply the IFFT filter:

Because the output of the FFT/IFFT is monochrome, you need to add the original colors. Move the original scan above the current layer, use a little Gaussian Blur (~1.5 pixels) and switch the layer mode to "Color":

Here you can see the difference (I used bi-linear scaling for both pics so you can see the missing moiré effect)