Can scanner large-area spatial crosstalk be corrected, and are any desktop scanners designed to reduce it?
Asked 11/23/2018
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Large-area spatial crosstalk is the scanner behavior described in IEC 61966-8 where nearby bright or dark areas influence the measured color/tonality of adjacent areas. In practice, this can make scanned photos less colorimetrically accurate, especially in images with broad, simple regions such as a bright sky next to a darker subject.
For example, on an Epson V850, identical gray patches can scan differently depending on whether they are surrounded by white or darker tones, suggesting that internal reflections and scattered light are affecting the reading.
Are there any reflection flatbed/desktop scanners that specifically address this in their hardware design, or any software tools that can correct or compensate for large-area spatial crosstalk after scanning?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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UPDATED The program has been updated to work with a range of scanner geometries and is no longer limited to the Epson V850. This is accomplished by creating a custom scanner reflection matrix calculated from a specially printed page. A tif image of this calibration page is provided for printing and then scanned which is used to create a scanner specific matrix. See the github link for operational details, description, and code.
Also included is a stand alone executable in a release.
This is a partial solution in that it only works for the Epson V850.
In the case of the V850, I've put together a program in C++ on github tailored to the Epson V850 which models the neighboring, reflected light and subtracts it from the image. However, this uses a model specific to the Epson V850. It corrects most of the large area spatial crosstalk as you can see from the attached image's improved L* value consistency. Unfortunately, this program uses a model that is specific to the V850 design and does not work well on other scanners with differing aperture designs. It does, however, work quite well on a variety of media such as matte, glossy and semigloss. There is some variation scanning different paper surface types but it is surprisingly small. At least with the V850. I'm looking for a more general solution.
Originally by user58107. Source · Licensed CC BY-SA 4.0
user58107
7y ago
0
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Based on the answers provided, a practical correction does exist in software, but it is limited and scanner-specific.
One community answer describes a C++ tool that models reflected neighboring light and subtracts it from the scan. It was originally built for the Epson V850, then updated to support a wider range of scanner geometries by creating a custom reflection matrix from a specially printed and scanned calibration page. That makes it a partial software solution rather than a universal fix.
So, from the provided answers:
- Yes, software correction is possible.
- It requires calibration for the specific scanner.
- It is not presented as a built-in feature of desktop scanners in general.
No answer identifies a particular reflection scanner whose hardware design fully eliminates or specifically advertises correction of large-area spatial crosstalk. In general, this kind of error is tied to flare/internal reflections in the scanner optical path, so compensation is most realistic through profiling/calibration and post-processing rather than expecting perfect correction from generic scanning software alone.
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