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Chapter 11 ∣ Color
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humans, approximately 10% of males and about
1% of females experience some degree of color
blindness. Color blindness is the inability to tell
colors apart. Knowing these statistics can help with
the decision-making process regarding color.
A person with normal vision has cones that
respond to all three of the additive primary colors
(RGB). A color-blind person lacks one, two, or
all three types of cones. Most color-blind people
have dichromatic vision and can see only yellows
and blues. They confuse reds with greens, and
some reds or greens with some yellows. Very few
people are truly blind to all colors. Those who are
completely color blind see only in shades of white,
gray, and black, and are said to have achromatic
vision.
Vision Fatigue
Random retinal impulses and involuntary rapid
eye movements are essential to vision and keep
the vision system perpetually active. Vision soon
fades when an image becomes optically fixed on
the retina. Movement of the eye sweeps the light
pattern over receptors to continually signal the
brain that the image is present. However, overuse
fatigues the system and can impair color judgment.
For example, viewing a saturated color for an
extended period of time causes a second color to
appear different because vision fatigue subtracts
some of the first color from the image.
Aging
Even with the complete absence of light,
random retinal impulses reach the brain. This
continuous background of random activity creates
a problem for the mind. The mind must decide
whether the activity is “noise” or information.
Internal visual noise increases with age and is
partly responsible for the gradual loss of visual
discrimination. Aging also impacts visual accuracy
and adaptation.
Viewing Conditions
In addition to vision deficiencies and variations,
external conditions also affect color judgment.
External variables include diverse lighting types,
different substrates, disparate viewing angles,
unconventional illumination angles, the size and
shape of the color area, the paint color on walls,
and even the color of clothing, Figure 11-34.
Because color vision requires sensory data, it is
impossible to actually remember color; we can only
compare color. However, accurate color comparison
is almost impossible unless items are viewed under
identical viewing conditions.
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Figure 11-34. Differences in viewing conditions under 2500 K,
5000 K, and 6500 K illumination.