Color Vision #1 Flashcards
(33 cards)
The scientific study of color is considered to have started with
Newton. He experimented with prism.
Retinal organization can be considered __ or __
Centripetal from photoreceptors to primary visual cortex or Lateral (horizontal and amacrine)
Purkinje Shift
The change in peak sensitivity observed when
X: wavelength
Y: Relative excitation level
What is the principle of univariance?
The absorption of a long wavelength quantum has the same effect on a receptor as the absorption of a short wavelength quantum.
One a quantum of light is absorbed, all info about wavelength is lost. Think about M and M example.
The probability of absorption depends on
Wavelength and PR class (either S, M, or L)
Wavelength is a ___ attribute, color is a ___ attribute.
Physical, perceptual
Intensity is a _____ attribute, brightness is a ____ attribute
Physical, perceptual
Object color is related to
The wavelength of light reflected from an object. Ex: a blue water bottle absorbs all colors, except blue. It reflects blue.
color mixing addition
RGB and lights obey addition. When mixing light, you will most likely get white. When mixing RGB, you will get Cyan, Magenta, Yellow and white.
Color mixing subtraction
CMYK and paints obey subtraction. When mixing paint, you will get the result of the two colors you had in common. Ex: mixing yellow (red and green) with magenta (blue and red), you will get red (which is what the two colors have in common).
Metamers
Two or more stimuli that have the same color but have different wavelength compositions. Color will change based on the light source landing on it.
Metamer properties (3)
Scalar: If you increase intensity of both metamers, they will still be metamers.
Addition: If you add the same wavelength to both metamers, they will still be metamers.
Associative: If a 3rd meatier is created for 1 metamer, all 3 will be metamers.
Spectral color vs non spectral color
Spectral: Obtained directly by prismatic decomposition of sunlight.
Non spectral: Not present in sunlight. Can be obtained only by mixing spectral colors. Some purples.
Color circles, triangles, and cubes provide ___ description of color matches
Qualitative
Shows that 2 colors may not be sufficient to make color matches. May need to change saturation. May use to use negative colors- take some color away and move to other side of bipartite field.
Complementary colors
any 2 colors that when added together, produce a neutral color (black, grey, white). On opposite sides of white in color triangle/circle/cube.
Red: Cyan (KU)
Green: Magenta
Blue: Yellow (KU)
Munsell term for hue
Wavelength
Munsell term for saturation
Chroma
Munsell term for brightness
Value
On a cylinder, where would hue, saturation, and brightness be?
Hue: around the rim
Brightness: Vertical axis. White at top. Black at bottom.
Saturation: Center to periphery. Center is desaturated. Periphery is saturated.
Color purity
The physical correlate of saturation, which is perceptual. Describes the proportion of pure, dominant spectral wavelength energy relative to the amount of achromatic light.
Color purity= wavelength you are interested in/ (wavelength you are interested + White wavelength)
Values for color purity
0
1
and 0-1
0= completely white/achromatic 1= completely pure. No achromatic light 0-1= contains some white/achromatic light.
Color mixing. For each wavelength matched, there is a set of 3 proportional values (primary colors) that add up to ___. This specifies the proportion of each primary color. These values are referred to as tri-stimulus values.
1.0
Tristimulus values plotted against spectral wavelength results in a graph that looks like
Red dips into a negative zone. Must be put on other side of bipartite circle. In order to bypass this, imaginary colors were created
What are imaginary primaries and why were they created?
imaginary primaries were created to get rid of the negative red value from the tristimulus graph.
However, values go outside of the value one.
