[See part 1 for bibliography]

[Hunt, p35-36]
"In spite of the inabilty of simple trichromatic methods to
render all colours colormetrically correct, it is often the
exception, rather than the rule, for the result to *look*
incorrect. Moreover, measurements tell us that the main defect is
that colours are rendered insufficiently vivid (because of the
unwanted eye-responses, see Fig. 2.3) and, in the case of
subtractive reproductions, too dark (because of the unwanted dye
absorptions, see Fig. 4.1); and yet the user often feels that,
far from the colors being too pale and too dark, there is rather
a tendency for them to appear, if anything, too vivid and too
bright, and the process is accused of exaggerating the colours.
In short, measurement defines she shortcomings of the process,
but when the photographer exposes a colour film or the viewer
looks at his tube, the defects often seem to have disappeared."

"To explain this apparent anomoly it has to be remembered that,
although colours may be conveniently defined in terms of physical
quantities such as spectral transmission and reflection curves,
they are perceived as sensations in the mind. We must therefore
consider the psychological as well as the physical side of the
story."

[Hunt, p36]
"It is only on rather special occasions that the reproduction and
the original are seen side by side; more usually the reproduction
is seen at a different place or time, and the time interval may
vary from a few hours to several weeks or even months or years.
The human memory therefore plays an important part. It might be
thought, then, that the process involved in appraising colours in
a reproduction consists of making mental comparisons between the
sensation produced in the mind by the reproduction, and a
recollection from the memory of the colour sensation produced by
the original object at the time when the picture was taken, It
is, however, a fact that the average person generally feels
competent to appraise the colours in pictures taken by people
other than himself, of objects which he has never seen, at times
when he was not present. This implies that colours in a
reproduction are not generally appraised by comparing them either
with the original object, nor even with some mental recollection
thereof. By what means are then then judged?"

[Hunt, p37]
"In short, our standard of comparison, a recollection of the
usual colour of green grass, is an extremely vague one, and,
consequently, provided that the reproduction of the green grass
is included somewhere in the range of colour sensations produced
by actual samples of green grass, we are satisfied."

[Hunt, p42]
"Thus a pale red tomato, for example, is more acceptable in a
reproduction than an orange or a magenta one. Correctness of hue
would, therefore, seem to be more important than correctness of
saturation. Moreover, the variations in saturation which occur in
natural colours are generally similar to those produced by adding
white light uniformly over the whole field of view. Hence, if, in
a reproduction, all colours are desaturated by about the same
amount, one would expect the result to look more natural than if
colours of different hues and saturations were desaturated to
different extents, so that some colours shone out like signal
lights, while others were grossly desaturated."

"The above considerations would seem to suggest that, as far as
colour is concerned, the requirements for a successful colour
reproduction are, in order of importance:
(1) Correctness of hue,
(2) Correctness of tone reproduction,
(3) Approximately equal saturation of colours of all hues,
(4) Approximately proportional saturation of colours of all
saturations."

[Hunt, p43]
"We can now summarize the situation. For fundamental and
unavoidable reasons, simple trichromatic methods cannot result in
colorimetrically correct colour reproduction, and the errors
inherent in most systems are considerable when measured
physically. But when the colour of an object in a colour picture
is appraised by an observer, it will generally look acceptable,
provided it falls somewhere within the range of colours which
that object customarily exhibits in everyday life. Practically
all colours met with in everyday experience are subject to wide
variations in hue, lightness and saturation, and this means that
no precise colour standards of familiar objects can be carried in
the memory. In particular, the variations in saturation are very
great and this obscures the unavoidable tendency of all processes
to produce losses in saturation."

[Hunt, p165]
"The ultimate test of any colour reproduction is the opinion of
the person who views it. But opinions differ, and, in cases
where dissatisfaction is felt, the viewer often finds great
difficulty in saying exactly why he does not like the sensations
which he experiences  when looking at the picture. Trained
observers may feel more competent to name the faults in a
reproduction, but training often makes an observer especially
sensitive to certain faults which have been prevelant in his
experience, while other faults, equally bad to a naive (but less
articulate) observer, he may overlook. A scientific approach to
the problem, though difficult, has therefore to be attempted."

*****"Memory Colors"*****

[Yule, p256-7]
"These will probably be flesh, green foliage, blue sky, and a
white cloud... These particular objects are not usually
encountered in graphic arts problems where a picture is to be
reproduced, but they are included here because of their
importance in color photography."

[The above sounded very strange to me when I first read it.
I think what he means is that we're not reproducing the color of
the object, we're reproducing the color of a *photograph* of the
object, so we're only dealing with colors that the film can
reproduce. For digital cameras, replace "film" with "CCD".]

[Hunt, p44]
"In fact, some workers have reported that otimum reproduction of
some well-known colours, such as skin, is achieved when a
definite difference exists between the original and reproduction
colours (MacAdam, 1951; Bartleson and Bray, 1962)."

[Hunt, color plate following p170]
"Good reproduction of Caucasion skin colours requires careful
control of hue: although real Caucasion skin varies towards
yellowish hues with sun-tan and towards more magenta hues with
flushed areas, the subtle changes of hue in these directions from
one area to another are important, hence the tolerances may not
be large; in the green and purple directions the tolerances are
usually quite small (see Section 5.6)."

[Hunt, p180]
"There is a considerable body of evidence that for Caucasian skin
colour the above concepts must be supplemented to allow for the
fact that a sun-tanned appearance is generally preferred to
average skin colour (MacAdam, 1951; Bartleson and Bray, 1962).
There may also be other colours where similar considerations
apply; for instance, blue sky and blue water are usually
preferred in real life to grey sky and grey water; most colour
films are sensitive to ultraviolet light and hence tend to
increase the blueness of sky and water relative to the saturation
of the other reproduced colours, but such a tendency, if not
overdone, may well be preferred to a more consistent
reproduction. It may also be desirable to introduce other
distortions of colour rendering to create mood or atmosphere in a
picture."

[Hunt, p181]
"It is clear from Fig. 11.7 that, for reflection prints, the
preferred skin colour lies, as expected, on the yellowish
(sun-tanned) side of typical average real skin (Thomas, 1973),
but the difference is small; and the preferred grass colour lies
on the yellowish side of typical average real grass (Thomas,
1973), but again, the difference is small. The chromaticities for
real skin and grass lie within the area of acceptable colour
reproduction, and this suggests that, for these colours,
colorimetric and preferred color reproduction are similar
(although the relative luminances are rather different for
grass). But, for the blue sky colour, although the dominant
wavelength of the preferred and real (Hendley and Hecht, 1949)
colours are closely similar, the preferred colour has an
appreciably higher purity."