Does profiling a printer with a scanner work well?

Started 2 months ago | Discussions thread
technoid Senior Member • Posts: 2,276
Re: Does profiling a printer with a scanner work well?

Gesture wrote:

How does the spectrometer do it differently from the flatbed scanner?

XRite's, and other's, spectros measure a small region inside the patch and are not normally affected by the colors of surrounding patches. They measure the reflectance of light over a large range of wavelengths then use that data to construct values that conform to average human color vision. Google CIEXYZ for details of the math.  Some of the cheaper ones, like the old I1Pro, can misread but still work quite well if one's hand motion is smooth. Spectros take multiple snapshots at tiny fractions of a second that contain the spectral reflectance of the patch color over a tiny area just 1 to 2 mm in diameter. The program looks at this data stream and separates out the samples taken that are completely inside each scanned patch.

A flatbed scanner illuminates a strip as it scans from top to bottom. Light that illuminates this strip then reflects off of nearby surfaces, especially the frosted white strips or light pipes that distribute and illuminate the paper. This light then winds up adding to the overall light that is illuminating the paper being scanned and is how nearby colors impact the scanned RGB values of a patch. I've seen this impact the CIEXYZ value(s) by well over 10%. A complete non-issue with a spectro.

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