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| shedding of electromagnetic radiation by a very hot material |
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| idealized material that is a perfct absorber and emitter of energy, absorbs and emits energy equally at all wavelengths. Will appear "colorless" or white after they reach temperature of 2500K, not visible to human eye |
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| emission of light stops at same time flow of energy is interrupted. Visible light is absorbed and then emitted at a higher wavelength |
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| material capable of storing energy, emit light after energy source is interrupted |
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angle of incidence is equal to angle of reflection, type of scattering.
Perfect material does not exist |
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change in direction of light due to rough surface materials. Occurs in atmosphere as a result of water droplets.
Perfect material does not exist.
depends on size of particle and wavelength of light.
Dependent on thickness of atmosphere it has to penetrate |
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| unimpeded passage of light through a transparent object |
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denotes a change in direction of photons when passing from one medium to another. Causes a change in the light's direction that is dependent on the wavelength.
Photons of higher energy change direction more strongly than those of lower energy. |
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| temporary splitting light waves into parts that are later recombined. Usually in form of transparent film, can cause iridescence |
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| combination of scattering and interference, influenced by sharpness of edge |
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the transfer of energy from photons to matter.
Blackbody is perfect absorber, others are selective.
Substances appear colored because they selectively absorb some colors and reflect others. |
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| reflectance factor curves (spectral reflectance or transmittance curve) |
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| shows how much light coming into contact with a surface is reflected back |
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| quality which describes the extent to which a color differs from a gray of the same value |
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| Commission International de Eclairage (Illumination), organization which recommended the standardization of spectral power distributions as illuminants and the numerical representation of the eye and brains's perception of color (standard observer) |
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| average color perception ability of human population |
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X = total red stimulus
Y = total green stimulus
Z = total blue stimulus |
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| visual perception that can be described by color names |
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| color of a blackbody ( object whose color is dependent on its temp, not its composition) when heated |
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| quality of color which we describe by names |
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| a light defined by a spectral power distribution, which may or may not be a physical light source |
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| spectral power distribution of a standard source, approximation of average daylight |
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| part of light is scattered and part is transmitted through object |
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| scattering is coupled with absorption and is so intense that no light passes through |
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| typical incandescent light |
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| close representation of daylight (manufactured) |
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| x, y, z (with lines over it) |
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| tristimulus for standard observer |
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rods- work in low light, cannot resolve sharp images or color. Absorbs wavelength b/w 400-510nm
cones- decipher color and resolve sharp images, need higher light levels |
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| Perception of color depends on imbalance between the stimulation of different kinds of cone cells |
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| Test for color blindness, subject tries to read numbers or shapes made of dots on a similarly dotted background |
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| Fransworth-Munsell 100 Hue Test |
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| Test for color blindness, subject tries to order Munsell color chips to make a hue progression from red to blue |
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(visual purple) chemical substance responsible for visual signals in optic nerve.
Undergoes a molecular change triggering a response in rod cells.. |
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| front surface of the eye, clear transparent tissue that covers the iris, provides 2/3 of the refractive power of the eye and is the light admitting window of the eye |
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| a small depression in the retina of the eye where visual acuity is highest. The center of the field of vision is focused in this region, where retinal cones are particularly concentrated. |
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| colored "diaphragm" of the eye, which constricts and dilates the pupil to control the amount of light let into the eye |
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| primary processing center for visual information received from the retina of the eye, found inside thalamus of the brain |
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| crystalline structure responsible for focusing light onto the retina. Changes shape slightly in order to change focus for objects near and far |
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| bundle of nerve fibers located at back of the eye, responsible for taking the information from the retina as electric signals and delivering to the brain where information interpreted as a visual image |
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| responsible for controlling the amount of light entering the eye. absence of obstacles and allows light to enter the eye through the iris |
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| thin tissue lining the innermost wall of the eye, hits retina and converted to electrical signals which are carried by the optic nerve to the brain |
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| Color of object depends on... |
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| light source, object, combination of eye and brain of the viewer, color of surrounding area, length of time person looks at object, color seen immediately prior to viewing, what you hope to see, surface roughness |
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measures color by percentage of black (B), white (W), and full color (C) on a spinning disc.
Point in space represented by C, W, B, all percentages.
System uses dominant wavelength, purity luminance to measure color |
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| used for matching rather than mixing colors. Based on 6 primaries- white, black red, green, yellow, blue |
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Describes all possible colors in terms of hue, value and chroma.
1450 colors in 40 hues
Hue expressed by number and letter (numbers 1-10 for value, letters taken from 5 different hues- red, blue yellow, green violet and adjacent pairs.
Hue represented by page, hue, value, chroma (2GY78) |
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| Advantages of Munsell System |
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Definition
o Agreement to equal visual perception
o Notation is not linked or limited by existing samples
o Any conceivable color can fit into the system
o Easy to replicate book year after year if not exposed to light or chemicals |
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| Disadvantages of Munsell System |
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Definition
• Disadvantages
o Colored sample and the chip from the collection will usually be made from a different colorant…will match under one light and not under another
o Samples fade and change overtime |
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| CIE Chromaticity Diagram System |
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Defined spectral power distribution for standard illuminant and spectral color matching as a function of a standard observer
uses spectral locus (chromaticity diagram)
X, Y, Z describe color, x, y, z describe chromaticity coordinates
system best for comparing rather than mixing colors |
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| Chromaticity Diagram (Spectral Locus) |
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Definition
describes color in terms of luminance and chromaticity. Primary colors occur on top.
Diagram used to measure colors in CIE system |
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| Advantages of Chromaticity Diagram |
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Definition
o We can locate dominant wavelength
o Can calculate the purity
o White point is near the center of the diagram
o Standard observer z is equal to zero for a large wavelength range. Therefore colors with a wavelength greater than 580 Z is negligible and the color can be described by only X and Y |
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| Disadvantages of Chromaticity Diagram |
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Definition
o No physical samples – color only represented by number
o No steps of equal visual perception – much larger area of green on the chart than red and blue
o Useful to see if two colors match, if not how they are different from each other
o No unique position for black (Munsell has black at bottom of the space)
o We can see where different colors lie on a chart and how different they are from each other |
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• Purity- distance from the illuminant point to sample point divided by that from illuminant point to spectral locus
• P =__a__
a + b |
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• Dominant wavelength- wavelength of the spectrum color whose chromaticity is on the same straight line as the sample point and the illuminant point
⋌ represents wavelength |
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| o Sample lies between the illuminant’s point and the purple boundary connecting the ends of the spectrum locus c⋌ |
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| Metamerism- two colors match if they have the same tristimulus values for a given illuminant and observer. When two objects that have different spectral reflectance curve they match if their CIE tristimulus values are the same for a given illuminant and observer (stripes experiment in light chambers) (sample has different colors in it, can look the same or different based on what kind of light source they are put under) |
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| Flare- two colors change when put under different light source. Samples change color, but both are always the same color! |
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