What is it?
"Large areas of spatial interference" is the terminology used by the IEC standard for scanners, 61966-8. Refers to the effect of nearby colors that change the scanned colors to neighboring colors.
What problems does it cause?
The effect can produce large differences in the colors of the scanned photos, which makes it sometimes impossible to scan a photo and obtain a colorimetrically accurate image file. These are not often noticed in complex photos, but some are quite susceptible. A scanned image of a hot air balloon against a bright sky will tend to brighten the sky brighter than the globe.
Precise reproduction is highly desired for, among other things, the duplication of precision and the retention of historical images.
Here is a scanned image of a moderately high end, V850 Epson Scanner. It is large, the displaced L * values are labeled below each circle. The three circular patches on the left were printed just like the three on the right. The lightest were RGB (240,240,240) while the darker ones were RGB (118,118,118). Circles surrounded by white have scanned L * s about 6 higher than the ones to the right. This change is for "Large area spatial interference".
This problem is caused by the light reflected in the nearby parts of a document, scattered and bounced off the translucent illuminated white rails on either side of a horizontal aperture through which the CCD scan is captured. It is as if the Lux levels in the white surrounding area on the right side increase by more than 20%, the increase in light needed to increase L * from 85.7 to 92.7.
Question: Is there a reflective desktop scanner that has addressed this problem in its design and / or is there any software that corrects or seeks to correct this defect?