Scanners, textures, scratches, cracks, silvering

[0lBaldy]

Flatbed Scanners and rough surface paper textures, scratches, cracks, tears/rips and "silvering" (compiled from various Forum threads @ RetouchPRO)

Scan at a high resolution in color with all adjustments turned off. The preference would be to scan at 600 dpi to 1200 dpi or higher, 16bits/channel, RGB. Even if it is a B/W or Grayscale picture, it is better to scan in color since the color channels may contain details that might otherwise get lost. The reason for such a high resolution is you may want to print larger and also you want to be able to see the damage at pixel level to make repairs. Extra information can sometimes be the difference between seeing how to do a repair rather than having to guess at it. When the repairs are done you can downsize to 300 dpi at print size and save.

When you let the scanner automatically do any processing on the data, it will most likely round off or clip/lose some information which may be useful to applications which have the capability to process high bit depth images.

Flatbed lighting utilizes a wide directional light source and amplifies the flaws in the surface of the original, casts long shadows in one direction. Acquiring a second scan from a different direction will light the surface defects differently... So scanning from another direction and merging them together will 'cancel out' the unwanted pattern due to the different lighting. Blending the two together in Photoshop or other imaging software can make use of this often unwanted 'feature' of flatbeds and surface grain/texture/reflections/cracks.

The following may help get a better scan with flatbed scans of rough surface textures (paper textures, scratches, cracks, tears/rips)... or ... very OLD photos (Tintypes or even modern silvered papers, etc.) that cast a reflection from what is called "silvering" on the surface of the photo. You can see it if you hold the photo at an angle to reflect light off of the surface. The light source that scanners use reflect off of silvering, and that reflection then becomes part of the image.

Turn off all automatic scanner enhancement settings and anything that auto fixes. No sharpness, no levels, no tone or saturation adjustment, no brightness or contrast adjustment, no dust & scratch removal, no descreen or denoising or despeckle, no color adjustment, no auto anything. All of that can and should be taken care of in photoshop. Then save the raw scan preferably as an uncompressed tiff or psd at full size. Take the raw scan and import it into Photoshop or appropriate image processing software and make your own adjustments if you need them.

The scans should be straight against the ruler edge of your scanner if possible.
Scan once as normal, then try a 180 degree flip and another scan (ensure straight scan edges etc.).
Drag the second scan image into the first scan image
Change top layer to difference mode
Use free transform to flip top layer 180 degrees
Push, prod and rotate until it goes black (it is now registered/lined up with the first scan), hit enter to keep transformation of transform
When aligned perfectly... change the layer mode from difference to lighten or darken mode, depending on the artifacts.
Combine/merge/flatten into one image/layer

* Another approach is to try a second scan that is 90 degrees offset to the original scan, then rotate that back and align and blend as above.

You might even make different passes like a dark scan, and a light scan to capture all the detail possible to be combined later.

For "silvering" the best results would be to take a picture of the photo with a digital camera, if you are careful to light the photo so that no silvering shows you will see past the reflections.



Tutorials:
Scanning to reduce surface texture or silvering

Scanning made Easy

[Peter Byrne]

This is a very thorough tutorial which im sure is going to help a lot of restorers including myself. I have approached the problem of texture in a similar way myself, but it's good to get another take on dealing with the problem.

Thanks 0lBaldy


Regards

Peter

[Mchilly]

Very informative, thanks for sharing a good tutorial