[See part 1 for bibliography]

[Billmeyer & Saltzman, p106]
"Always Remember That Nobody Accepts or Rejects for Color Because
of Numbers: It Is the Way It Looks That Counts."

[Sipley, p84]
[Quoting Ives, writing about his 'Polychrome' process in 1933]
"In consequence some of the most beautiful color photographs have
been made by the Polychrome process by careful balancing of
exposures and densities without recourse to reprinting, redyeing,
or retouching. But it is also true that equally beautiful results
have been obtained when miscalculated exposures and densities
have necessitated such compensations; and the facility with which
they can be made in the Polychrome process is a revelation to
anyone who first sees such work done by an expert."

[Billmeyer & Saltzman, p166-7]
"First, if the system is going to work, the entire coloring
process must be under complete control to a high degree of
accuracy. Before even considering trying a system out, much less
purchasing one, the prospective user should demonstrate, using
instruments, that he can in fact go through the entire coloring
process from incoming colorant testing to final product out the
door with a reproducability, in terms of color differences, that
is satisfactorily small. Believe us, this is not easy, and many
prospective users of computer color matching have (or should
have) stopped right there."

[Hunt, p34]
"It will be realized that these three expedients cannot correct
for the fundamental limitations of the process, which spring from
the nature of the colour machanism of the eye and the shape of
the spectral absorption curves of the best available cyan,
magenta, and yellow dyes. What is claimed for modern subtractive
processes is that they produce pleasing colour pictures, and that
the inevitable inaccuracies are balanced in such a way as to be
least noticable."

[Billmeyer & Saltzman, p66]
"Unfortunately, there appear to be strong prejudices associated
with industrial and national preferences which have prevented
agreement on exactly what the 'perfect' white is, and which
directions of departure from it (toward blue, yellow, red) are
preferred or avoided. As a result no single formula for whiteness
is now widely accepted."

****Color Rendering and Metamerism****

[Billmeyer & Saltzman, p176-7]
"Nimeroff (1965) suggested a means of calculating a general index
of metamerism from differences in the spectral curves of two
samples. It is well known (for example, Wright 1969, Thornton
1978b) that these curves must cross at least three times if the
samples are metameric. One gets the general feeling that the more
crossings there are, and the closer the curves approximate one
another, the less must be the degree of metamerism."

[Billmeyer & Saltzman, p177]
"Just as the color-rendering index rates sources used for the
critical examination of colors, so one could devise a
color-preference index for those used for the appreciative
viewing of colors. Judd (1967) proposed such an index, in which
the base from which the color differences are calculated is the
set of colors people would prefer to see, rather than the actual
colors of the test samples-- bluer skies, greener grass, ruddier
Caucasion flesh tones, and so on."

[Billmeyer & Saltzman, p178]
"The CIE color-rendering index was designed in studies of, and
works best for, sources with continuous spectral power
distributions. However, a number of modern energy-efficient
flourescent sources, known as prime-color lamps (Haft 1972) and
sold under various trade names such as Westinghouse's Ultralume,
have discontinuous distributions such as the one shown in page
174. The various indices described in this section, for both
metamerism amd color rendering, do not appear to work well for
sources with these unusual spectral power distributions.

*****Variation in "Normal" Color Vision*****

[Billmeyer & Saltzman, p53]
"In the figures on page 54 we consider only the change in
illuminant, for convenience, but we wish to emphasize that the
change in observer to another, *all with 'normal' color vision*,
is equally important (Billmeyer, 1980a), a fact all to often
overlooked!"

[Billmeyer & Saltzman, p72-3]
"Differences among observers, all with normal color vision by the
usual tests, can lead to at least as great a variation in the
judgement of what constitutes a match as can the use of different
light sources (Brown 1957, Nimeroff 1962, Smith 1963, Billmeyer
1980a, Kaiser 1980). Unless observer differences are recognized
and taken accound of, for example, by prior agreement, no amount
of standardization of light sources can lead to satisfactory
results. Again, the importance of this often unrecognized
variable cannot be overemphasized."

[Billmeyer & Saltzman, p174-5]
"What is more important, but not yet widely taken into account,
is the large spread in observer characteristics within the range
considered to have normal color vision. Our warning of the
seriousness of this spread in the first edition of this book was
largely ignored or disbelieved. We have recently documented it
(Billmeyer 1980a) using a Color Rule: When observers of a wide
range of ages (roughly 20-60) are considered, the spread in their
settings on the Color Rule is as wide as the difference between
6500 K daylight ant "horizon sunlight" in a standard
color-matching booth! If the reader has any doubts that this is
an important variable in colorimetry, let him observe the
difference in appearance of a metameric match using these two
sources!"

"It is well known that a major part of this spread among normal
observers results from the gradual yellowing of the lens of the
eye with increasing age. Nardi (1980) has followed up our
research to show that in a group of college-age observers (17-29
years old) the spread is about a quarter as great as that
indicated above."