CIE
Division 8 - TC8-03: Survey of Gamut Mapping Papers
Schläpfer (1994)
This document of the Swiss Federal Laboratories for Materials Testing
and Research (EMPA) gives data describing the "correlation between calculated
and measured values" for two gamut mapping algorithms for transforming
colours from transparencies to newsprint (i.e. a medium having a very limited
L* range - from approximately 35 to 80 [using absolute colorimetry] and
a maximum chroma of approximately 50). The following is the description
of the two algorithms reproduced here verbatim:
Model 1
-
Lightness: Linear compression based on the values of the substrate and
of Dmax.
-
Hue: Individual correction for each hue angle based on the values of primary
and secondary colours.
-
Chroma: Hue-dependent non-linear compression based on a lookup-table.
Model 2
-
Lightness: Identical with Model 1.
-
Hue: No correction.
-
Chroma: Non-linear compression based on a hue-independent empirical formula.
Unfortunately the document reviewed here does not give more detail on the
above algorithms. Nonetheless, Model 1 in particular bears some resemblance
to the model described in CARISMA (1992). This is an interesting fact,
as the former model is intended for going between transparency and newsprint
whereas the latter was developed on the basis of reproducing transparencies
on Cromalin proofs and as these two reproduction media have very different
gamut sizes.
Last updated: 17 August 1999 by Jan
Morovic