PRECISE COLOR
COMMUNICATION
COLOR CONTROL FROM PERCEPTION TO INSTRUMENTATION
Knowing color.
Knowing by color.
In any environment,
color attracts attention.
An infinite number of colors surround us in our everyday lives.
We all take color pretty much for granted, but it has a wide
range of roles in our daily lives: not only does it influence our
tastes in food and other purchases, the color of a person’s face
can also tell us about that person’s health.
Even though colors affect us so much and their importance
continues to grow, our knowledge of color and its control is
often insufficient, leading to a variety of problems in deciding
product color or in business transactions involving color.
Since judgement is often performed according to a person’s
impression or experience, it is impossible for everyone to
visually control color accurately using common, uniform
standards. Is there a way in which we can express a given
color* accurately, describe that color to another person, and
have that person correctly reproduce the color we perceive?
How can color communication between all fields of industry
and study be performed smoothly? Clearly, we need more
information and knowledge about color.
*In this booklet, color will be used as referring to the color of an object.
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Contents
PART
I
Why does an apple look red? ········································································································4
Human beings can perceive specific wavelengths as colors. ························································6
What color is this apple ?···············································································································8
Two red balls. How would you describe the differences between their colors to someone? ·······10
Hue. Lightness. Saturation. The world of color is a mixture of these three attributes.·················12
Hue, lightness, saturation. Let’s a color solid. ··································································14
By creating scales for hue, lightness, and saturation, we can measure color numerically. ·········16
Color meters make quantifying colors simple. ·············································································17
Let’s look at some color spaces. ··································································································18
Color meters excel at reporting even minute color differences.···················································22
Even if colors look the same to the human eye,
measurements with a color meter can point out slight differences. ·········································24
PART II
Differences in the color recognition process between the human eye and color meters·············28
What about the components of light (and color)? Let’s take a look. ··········································30
Lets measure various colors with a color meter. ·········································································32
Even though it’s actually the same color, it looks different. Why? ···············································34
Colors look different according to the light source. ······································································36
A complex problem: Metamerism ································································································38
Colors also look different according to the subject conditions and environment. ························40
Spectrophotometers solve these problems easily and quickly. ···················································43
Understanding important specifications ·······················································································44
Measuring Special Colors ············································································································52
Notes for Measurement (Subjects and Environment) ··································································54
PART III
New Color Difference Formula (CIE DE2000) ·············································································55
PART IV
COLOR TERMS ··························································································································59
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PART I
Let’s study color.
Even when we just look around, a wide variety
of colors is readily visible. We are surrounded
by an infinite variety of colors in our daily lives.
However, unlike length or weight, there is no
physical scale for measuring color, making
it unlikely that everyone will express it in the
same way when asked what a certain color is.
For example, if we say blue ocean or blue
sky, each individual will imagine different blue
colors, because their color sensitivity and past
experiences are different. This is the difficulty
with color.
We also do not understand the mechanism of
commonplace phenomena concerning colors
such as Why do apples look red?.
This section describes important and useful
information about colors.
3
Why does an apple look red?
4
No light, no color. The three elements of light, vision,
and object are necessary for us to perceive object color.
In total darkness, we cannot know color. If we close our eyes, we cannot see the color of an object. And
if there is no object, color does not exist. Light, vision, and object: if all three are not present, we cannot
perceive color. But how can we tell the difference between colors, between the red of an apple and the
yellow of a lemon?
5
Human beings can perceive specific
wavelengths as colors.
Wavelength
(m)
Broading
Shortwave
2
10
1
FM
Television
Radar
–2
10
–4
10
Infrared
–6
10
Visible light
Ultraviolet
–8
10
–10
10
X-rays
Wavelength(nm)
–12
10
780
γ -rays
Rad
700
–14
10
Cosmic rays
Yellow
600
Green
Blue
•The electromagnetic spectrum.
500
Indigo
Violet
400
380
6
Visible light
Orange
If we separate light into its different wavelengths, we
a spectrum. We can then the different colors
by mixing the separated wavelengths of light in varying
intensities.
Most people know that if we pass light from the sun through a prism, we a color distribution like a
rainbow. This phenomenon was discovered by Isaac Newton, who also discovered universal gravity.
This distribution of colors is called a spectrum separating light into a spectrum is called spectral dispersion.
The reason that the human eye can see the spectrum is because those specific wavelengths stimulate the
retina in the human eye. The spectrum is arranged in the order red, orange, yellow, green, blue, indigo, and
violet according to the different wavelengths*1 of light the light in the region with the longest wavelengths
is seen as red, and the light in the region with the shortest wavelengths is seen as violet. The light region
which the human eye can see is called the visible light region. If we move beyond the visible light region
toward longer wavelengths, we enter the infrared region if we move toward shorter wavelengths, we enter
the ultraviolet region. Both of these regions cannot be seen by the human eye.
Light is just one portion of the various electromagnetic waves flying through space. The electromagnetic
spectrum covers an extremely broad range, from electrical and radio waves with wavelengths of several
thousand kilometers to gamma (γ) rays with wavelengths of 10-3 nm and shorter. The visible light region is
only a very small portion of this: from approximately 380 nm to 780 nm*2. The light reflected from an object
and which we recognize as color is (with the exception of man-made monochromatic light) a mixture of light
at various wavelengths within the visible region.
*1 Wavelength: Light has wave characteristics wavelength is the
peak-to-peak distance of two adjacent waves.
Wavelength
*2 nm(nanometer): A unit of measure often used when discussing
wavelengths of light m(micrometer) is also
sometimes used.
1 nm=10 -9 m=10 -6 mm=10 -3 m
1 m=10 -6 m=10 -3 mm=103 nm
• A rainbow is d by sunlight passing
through fine water lets in the air, which
act as prisms.
7
What color is this apple ?
Red!
Hmmm.
Burning red.
I’d say
crimson.
Bright Red.
8
A color expression often means ten different colors to
ten different people.
“Name this color” is a very difficult thing to do.
If you show the same apple to four different people,
you are bound to get four different answers.
Color is a matter of perception and subjective interpretation.
