RE: calculating from abscol to relcol from L*a*b*
RE: calculating from abscol to relcol from L*a*b*
- Subject: RE: calculating from abscol to relcol from L*a*b*
- From: Marco Ugolini <email@hidden>
- Date: Wed, 22 Apr 2009 13:21:14 -0400 (EDT)
Tom Lianza wrote:
>As marco so correctly said:
>
>" In other words, one must convert from the measured Lab values to XYZ, then
>from XYZ back to Lab -- but this time using the XYZ coordinates of the
>measured reflective media white for the transform from XYZ to Lab, instead
>of D50 white point coordinates."
>
>This is correct algebra, but incorrect physics. If the paper white is the
>result of florescence, then each of the printed colors is affected by the
>colors specific transmission of UV.
Tom,
The question was "how to go from measured data to colorimetric data adjusted for a media-relative white point". And the procedure I pointed out works for that purpose.
As for the presence of fluorescence, that is yet another issue altogether, in my view. The point is that the procedure works for measurements of non-fluorescent substrates or measurements of fluorescent substrates taken with UV-excluded spectrophotometers.
Marco Ugolini
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