Why do dust and scratches show up more in dark areas when scanning color prints?
Asked 1/17/2021
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When I scan color prints, I notice that after descreening there seem to be many more visible dust spots, fibers, or scratches in the darker parts of the image, while brighter areas look mostly fine. Is this normal for flatbed scanning of prints, or does it suggest a scanner problem? I've cleaned up the scans in post, but I'd like to understand why it happens and whether there’s anything I can do to reduce it.
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
5y ago
2 Answers
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This can be normal when scanning pictures. The scanner works by shining a bright light onto the surface of the paper. Dust and fibers can easily reflect back into the scanning sensor, and are more easily visible against the dark contrast of darker areas of the image. Sometimes scratches or etchings on a paper may become more easily visible after scan than they were to the eye.
Try to carefully dust off your photos as best as possible with a soft brush, without being too abrasive. Also, try to carefully clean the scanner glass without leaving any glass cleaner residue behind. This should remove most of the major offenders of dust and fibers.
But, cleaning doesn't always get rid of everything. Some photo or scanning software have dust and scratch removal tools. You can also use photo editing software like Photoshop or Gimp to manually try to repair the photos.
Originally by user96930. Source · Licensed CC BY-SA 4.0
user96930
5y ago
0
Generated from our catalog & community — verify before relying on it.
This is usually normal when scanning prints, not necessarily a fault with the scanner. A flatbed scanner shines a bright light onto the photo surface; dust, fibers, and small scratches can reflect that light back to the sensor and become much more obvious in the scan. They tend to stand out more against dark image areas because the contrast is higher, while bright areas can hide them.
Descreening or other processing can also make surface defects and paper texture more visible than they appear to your eye.
To reduce it:
- gently dust the print with a soft brush
- clean the scanner glass carefully and avoid cleaner residue
- handle prints carefully to avoid adding scratches
- use dust/scratch removal tools in scanning or editing software if needed
So the effect is common with scanned prints, especially older or textured ones, and is mostly about reflected light and contrast rather than a scanner malfunction.
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