What is Color?
• Color is related to the wavelength of light.
If a color corresponds to one particular
wavelength, this is called a spectral color.
• =600 nm corresponds to a color, but
naming it is not an exact science….
– orange chrome, golden poppy, spectrum orange,
bitter sweet orange, oriental read, Saturn red,
cadmium red orange, red orange…
Newton’s Study of Colors
• Plague hit London in 1665 soon after Newton graduated from
Cambridge
• Went to his mother’s farm for two years and conducted optical
experiments
• Separated white light into colors with a prism
• Could have concluded that the colors were created in the prism
• Showed that wasn’t the case: used second, reversed prism to
recombine the colors to form white light
• Prism experiments made Newton famous
• Returned to Cambridge in 1667 and remained for 30 years
• Became Lucasian professor of mathematics in 1669
• A particular color sometimes corresponds to
a range of wavelengths
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–
–
–
–
Blue: 455 ~ 485 nm (460 nm)
Cyan: ~500 nm (blue-green)
Green: 510 ~ 550 nm (530 nm)
Yellow: 570 ~ 590 nm (580 nm)
Red: 620 ~ 670 nm (650 nm)
• Most of the time, however, we see nonspectral colors. We can see a color even
when the wavelength of the corresponding
spectral color is absent. There is more to
color than wavelength!
Intensity Distribution
• Most of the colors we see are not spectral
colors, but instead have a distribution of
intensity in wavelength.
• For example, a color green may contain all
other colors but with the intensity peaked at
the wavelength 530 nm.
• Our eyes cannot distinguish the colors that
are composite from spectral colors. (different
distributions may correspond to the same perceived color!)
Sample Intensity Distribution
Relative Intensity
-- Plots the relative intensity at each wavelength.
400 nm
500 nm
600 nm
700 nm
Historical Problems with Identifying
Colors
• Theoretical Problems
– Numerous color concepts
– Different theorists organize properties of color into different
functional systems
• Leonardo da Vinci (15th Century)
• Newton – discovered spectrum and devised color circle
• J.C. Le Blon – observed primary nature of red, yellow, blue and
described hues from mixing (1756)
• Moses Harris – published first color circle in full color (1766)
Different Color Wheels
• Color wheel 1
Various Color Classifications
Munsell Solves Color Problems!
• Albert H. Munsell
– Seascape painter of the 1890s
– Munsell System of Color Notation (1905)
– One of the color standards used by the US
National Bureau of Standards
– Used in science, industry, and art
What is the Munsell Color Tree?
• 3D Spherical Model
• Incorporates concepts of hue,
lightness, and saturation in one
model
• Organized in a numerical
classification system
• Inclusive of all colors – each
color has its own place
Munsell Color Tree
• Based on the 2D Color
Wheel
– Includes primary, secondary
colors, i.e. hues
– Can be expanded to
include intermediate hues
• Shows all variations of
colors/hues, which are at
full intensity on the wheel
Munsell Color Tree
• Lightness scale - the “trunk”
– The lightness/darkness of a particular hue
– Vertical arrangement: the trunk of the color
tree
• Nine levels of lightness
– 1 = black
– 9 = white
• Values of hues are compared with this
neutral gray pole
Munsell Color Tree
• Saturation
– Refers to
strength/weakness of a
hue at a certain
lightness
– Related to purity,
intensity
– Horizontal
arrangement: the
branches of the tree
• Fourteen levels of
saturation
– 1 = dullest, most gray
variation of the hue
– 14 = most intense, pure
state of the hue
Lightness and Saturation
Classification of colors
• Hue: main color. Associated with the
“dominant wavelength” in an intensity
distribution curve.
• Saturation: purity of the color.
Measures how much dominant wavelength there
is compared to the amount of white mixed in.
– Saturated: all intensity fairly close to the
dominant wavelength (spectral color is 100%)
– White or grey: completely unsaturated
• Brightness (light source) and lightness
(surfaces)
– Lightness has to do with the percentage of
incident light reflected at each wavelength.
(white: a lot of reflection; black: no reflection)
Color tree: The same position
has the same color independent
of the intensity!
–Trunk completely
unsaturated. Out from the
trunk, the degree of
saturation increases.
–The vertical axis is related
to lightness (a gray scale
from white at the top to
black at the bottom)
–The hue varies around the
tree (green,blue, red, etc.).
Saturated colors are the
“leaves” at the ends of the
branches.
Color Tree
Color in Art
Mark Rothko
(1956)
Orange and
Yellow
Henri Matisse
(1943-44)
Icarus (Jazz)
Josef Albers (1966)
White Line Square XIII
Piet Mondrian (1922)
Composition with Blue,
Yellow, Black, and Red
Marc Chagall
(1913)
Paris Through
My Window
The End