Reduce raster effect from old photo

This is a internal recipe, not a tutorial.

Scan at 9600 dpi (to enlarge a small photo)

Rotate the photo with 180 degree and scan again.

Place the second scan in another layer in Photoshop.

Rotate the second layer with 180 degree.

Use align layers function with 50% opacity of the top layer.

Flatten the image or respectively merge the 2 layers.

Apply a surface blur with the radius of 34 pixels and threshold of 100.

Resize the canvas (without re-sampling) to the desired size.

Re-sample  the image at 300 dpi, bi-cubic sharper (for print, and to reduce the blur effect).

Apply smart sharpen wiht the radius of 14.5 pixels (depends on the re-sampling ratio, should be the equivalent of the original blur radius)

Optionally adjust levels, with Black at 30.

I repeat, this was a personal recipe for a specific type of photo.

The idea is to scan at 180 degree. When you merge the inverted layers, the shadows are in opposite direction and naturally reduce the raster relief, but the raster is still present.

In order to reduce permanently the raster I used the blur / sharpen technique.

More advanced techniques use FFT. In my case I wasn’t successful with the FFT because I didn’t have time to learn the technique properly.