Notice for those using desktop reflection scanners that want more accuracy and
consistency.
Announcing a utility program that:
1. Corrects for errors due to internal scanner reflections that distort read
colors
2. When used with an i1iSis or i1Pro 2 spectro, and Argyll s/w creates
precision scanner input ICC profiles.
The problem with desktop scanners is that they illuminant a slice of the
scanner paper and, when the image region around the spot is being scanned is
very bright or colorful, reflected light from bounces off the frosted strips
that go across the top and bottom scanning slot.
Color shifts due to internal light reflection from the paper being scanned can
be surprisingly large. Here's an example with my Epson V850. Two 6mm on a side
squares where one is surrounded on all sides by 20mm of yellow and the other by
cyan shifts the unprinted white scanned Lab values such that there is 15 delta
E 1976 between the two. Each white patch is shifted in the direction of its
surrounding color.
I have designed a program that models this reflection spatially using a
calibration scan. It reduces the dE from 15 to 1 in the above example. The
model is a matrix that is used to estimate the cumulative colors reflected
nearby and is saved as a text file. This only needs to be done once for a
scanner and works well with all paper types such as matte, luster, and glossy.
I posted a Github public repo with C++ code that significantly improves the
ability of scanners to create high accuracy reproductions be removing
re-reflection errors. Additionally, it has the ability to read tiff patch
charts and create a CGATs file that is easily processed by Graeme Gill's
excellent profiling software to create an input scanner profile. The utility
When using this with my Epson V850 I consistently get scanned average delta E
values that are under .5 scanning prints I have made.
https://github.com/doug3236/scanner_refl_fix
doug
