CHAPTER 5: PERCEIVING COLOR Flashcards
Color vision
The ability to see differences between lights of different wavelengths
Visible Spectrum
The portion of the electromagnetic spectrum in the range of about 400-700 nanometers (nm)
within this range people with normal vision perceive differences in wavelength as differences in color
Spectral Power Distribution (SPD)
The intensity (power) of a light at each wavelength in the visible spectrum
Heterochromatic Light
Light that consists of more than one wavelength
Monochromatic Light
Light that consists of only one wavelength
Achromatic Light (white light)
Light containing wavelengths from across the visible spectrum, with no really dominant wavelengths
perceived as more or less colorless (i.e. shade of grey)
Spectral Reflectance
the proportion of light that a surface reflects at each wavelength
Hue
the quality usually referred to as “color”
the perceptual characteristic most closely associated with the wavelength of light
Saturation
The vividness, purity, or richness of a hue
Color Circle
A 2-D depiction in which hue varies around the circumference and saturation varies along any radius
Color Solid
A 3-D depiction in which hue varies around the circumfrence, saturation varies along any radius, and brightness varies vertically
Subtractive Color Mixture
A mixture of different-colored substances
called “subtractive” because the light reflected by the mixture has certain wavelengths subtracted (absorbed) by each substance in the mixture.
Additive Color Mixture
A mixture of different-colored lights
called “additive” because the composition of the mixture is the result of adding together all the wavelengths in all the lights in the mixture
Complimentary colors
Pairs of colored lights that, when combined in equal proportion, are perceived as a shade of gray.
Primary Colors
Any three colors of light that can be combined in different proportions to produce a range of other colors
Metamers
Any two stimuli that are physically different but are perceived as identical
Spectral Sensitivity Function
The probability that a cone’s photopigment will absorb a photon of light of any given wavelength.
Principle of Univariance
With regard to cones:
The principle that absorption of a photon of light results in the same response regardless of the wavelength of light.
Hue Cancellation
An experimental technique in which the person cancles out any perception of a particular color in a test light by adding light of another color
According to Hue cancellation, what are the 4 basic colors consisting of two pairs of opponent colors?
Red-Green
Blue-Yellow
Monochromacy
A condition in which a person has only rods or has only rods and one type of cone
In either case, the person is totally color-blind, perceiving everything in shades of gray
Rod Monochromacy
A condition in which a person has rods only with no cones
Cone Monochromacy
A conditon in which a person has rods and only one type of cone
Dichromacy
A condition in whcih a person has only two types of cones, instead of the normal three
the person has a limited form of color vision but cannot discriminate as many colors as a person with all three cone types
Ishihara Color Vision Test
A test using configuration of multicolored disks with embedded symbols
the symbols can be seen by people with normal color vision but not by people with particular color vision deficiencies
Protanopia
A condition in which a person has M-cones and S-cones but lacks L-cones
Deuteranoppia
A condition in which a person has L-cones and S-cones but lacks M-cones
Tritanopia
A condition in which a person has L-cones and M-cones but lacks S-cones
Achromatopsia
Loss of color vision caused by brain damage
