An earlier modeling study of the effect of changes in macular pigment
optical density (MPOD) on a wide range of surface colors is re-examined.
That study reported changes in local chromaticity variance and in color
spacing, some of which were incompatible with tritan-like confusions in
normals associated with high-simulated MPOD. This disagreement might have
arisen through the use of the von Kries correction for adaptation. The
analysis is repeated, using 1782 reflectance spectra of natural and
man-made colors. These colors are segregated into an array of 25 equally
populated cells in an analogue of the MacLeod-Boynton cone excitation
diagram. Removing the von Kries correction restores compatibility with
other experimental data. Differences between the results for normal and
anomalous trichromats, noted in the earlier study, are confirmed. An
analysis of local chromaticity variance across color space indicates the
presence of systematic patterns. The earlier study also reported
differences in results across observer types (for example, between normals
and protanomals) and this is addressed here by utilizing fundamentals
defined by a variable photopigment template. Chromaticities are computed
for the same 1782 reflectance spectra for normals and for a set of
protanomals (for whom the anomalous L pigment is shifted between the
normal L and M spectral locations). Colors are segregated into an array of
100 cells in an analogue of the MacLeod-Boynton cone excitation diagram.
Changes in chromaticity variance with MPOD for these cells are mapped for
normals and protanomals. Variance along the L/(L + M) axis is
sensitive to the number of cells used for segmentation. It also increases
with MPOD for normal observers but this trend reverses as the wavelength
of maximum sensitivity of the L cone shifts towards shorter wavelengths
(protanomalous locations).