Dive into the world of color and appearance measurement with our ultimate glossary!Whether you're a seasoned professional seeking to refine your knowledge or a beginner eager to master the essentials, this comprehensive guide covers all the key terminologies.From technical concepts like CIE color spaces and Delta E to appearance - related terms such as gloss and metamerism, we break down complex jargon into easy - to - understand explanations.Elevate your expertise today and gain a deeper understanding of this crucial field to enhance your work in industries ranging from manufacturing and design to quality control.
Are you often mixing up your basic color measurement terminology? Elevate Your Expertise: The Ultimate Glossary of Color & Appearance Measurement Terminologies and Threenh is here to help. Here are some common terminologies in color and appearance measurement:
CIE Color Space
The International Commission on Illumination (CIE) has defined several color spaces to describe colors in a quantitative way. The most commonly used ones are CIE XYZ and CIE Lab. CIE XYZ is a tristimulus value - based color space, and CIE Lab is derived from it, which separates color into lightness (L*) and color - difference coordinates (a* and b*).
Hue, Saturation, and Value (HSV)
Huerepresents the dominant wavelength of a color and is used to distinguish different colors such as red, green, and blue.
Saturationrefers to the purity or intensity of a color. A highly saturated color is vivid and pure, while a low - saturation color appears more muted or grayish.
Value(also known as brightness or lightness) indicates the relative lightness or darkness of a color, ranging from black (low value) to white (high value).
Color Temperature
Measured in Kelvin (K), it describes the color appearance of a light source. Lower color temperatures (around 2700 - 3000K) produce warm - yellowish light, while higher color temperatures (5000 - 6500K) result in cool - bluish - white light. This concept is widely used in lighting and display industries.
Delta E (ΔE)
It is a measure of the difference between two colors. A smaller ΔE value indicates a closer match between the two colors, and a larger value means a more significant color difference. In general, a ΔE of less than 1 is considered imperceptible to the human eye, while values above 3 - 5 are usually noticeable.
Gloss
It refers to the shiny or reflective quality of a surface. High - gloss surfaces reflect light strongly and appear very shiny, while low - gloss or matte surfaces scatter light and have a more subdued, non - reflective appearance. Gloss is often measured using a glossmeter and is expressed as a percentage or a specific unit depending on the measurement method.
Opacity
Opacity describes the degree to which a material blocks light and prevents objects behind it from being seen. A completely opaque material allows no light to pass through, while a transparent material has high light transmittance and low opacity. Translucent materials are in between, allowing some light to pass through but diffusing it so that objects behind are not clearly visible.
Texture
Texture refers to the surface characteristics of an object, including its roughness, smoothness, and any patterns or irregularities. It can affect the way light is reflected and scattered, thereby influencing the overall appearance of the object. Texture can be perceived visually and tactilely and is an important factor in determining the aesthetic and functional properties of a material.
Metamerism
Metamerism occurs when two samples appear to have the same color under one type of lighting condition but look different under another. This is because the spectral reflectance curves of the two samples are different, but they happen to match in a particular lighting environment. It is an important consideration in color - matching applications, especially in industries such as textile and printing, where products need to maintain consistent color appearance under various lighting conditions.
Absolute Reflectance Value
Reflectance value relative to the perfectly reflecting and perfectly diffusing surface, which is assigned a value of 1.0.
Absorption
Process by which light or other electromagnetic radiation is converted into heat or other radiation when incident on or passing through material.
Accuracy
Conformity of a measured result to an accepted reference value or scale.
Achromatic Color
A neutral color, such as white, gray or black, that has no hue. Also termed nonchromatic.
Additive primaries
Red, green and blue light. When all three additive primaries are combined at 100% intensity, white light is produced. When these three are combined at varying intensities, a gamut of different colours is produced. Combining two primaries at 100% produces a subtractive primary, either cyan, magenta or yellow: 100% red + 100% green = yellow 100% red + 100% blue = magenta 100% green + 100% blue = cyan See subtractive primaries
Angle of Incidence
The angle between the axis of an impinging light beam and the perpendicular to the specimen surface.
Angle of View
The angle between the axis of observation and the perpendicular to the specimen surface.
Appearance
A visual perception through which an object is seen to have attributes such as size, shape, colour, texture, glossiness, transparency, opacity, etc.
Artificial daylight
Term loosely applied to light sources, frequently equipped with filters, that try to reproduce the colour and spectral distribution of daylight. A more specific definition of the light source is preferred.
Attribute
Distinguishing characteristic of a sensation, perception or mode of appearance. Distinction is made between chromatic and geometric appearance attributes. Colours are often described by their attributes of hue, chroma (or saturation) and lightness.
Black
In theory, the complete absorption of incident light; the absence of any reflection. In practice, any colour that is close to this ideal in a relative viewing situation — i.e., a colour of very low saturation and very low luminance.
Brightness
The attribute of visual sensation by which an observer is made aware of differences in luminance.
Calibration
The graphical or mathematical relationship of a desired property to an instrument's output.
Chromatic
Perceived as having a hue - not white, gray or black.
Chromatic Attributes
Those attributes associated with the spectral distribution of light, hue and saturation.
Chroma/Chromaticity
That part of a color specification which does not involve luminance. The intensity or saturation level of a particular hue, defined as the distance of departure of a chromatic colour from the neutral (grey) colour with the same lightness value. In an additive colour-mixing environment, imagine mixing a neutral grey and a vivid red with the same value. Starting with the neutral grey, add small amounts of red until the vivid red colour is achieved. The resulting scale obtained would represent increasing chroma. The scale begins at zero for neutral colours, but has no arbitrary end. Munsell originally established 10 as the highest chroma for a vermilion pigment and related other pigments to it. Other pigments with higher chroma were noted, but the original scale remained. The chroma scale for normal reflecting materials may extend as high as 20, and for fluorescent materials it may be as high as 30.
The ratios of each of the three tristimulus values X, Y and Z in relation to the sum of the three — designated as x, y and z respectively. They aresometimes referred to as the trichromatic coefficients. When written without subscripts, they are assumed to have been calculated for illuminant C and the 2° (1931) standard observer unless specified otherwise. If they have been obtained for other illuminants or observers, a subscript describing the observer or illuminant should be used. For example, x10 and y10 are chromaticity coordinates for the 10° observer and illuminant C.
A two-dimensional graph of the chromaticity coordinates (x as the abscissa and y as the ordinate), which shows the spectrum locus (chromaticity coordinates of monochromatic light, 380 nm -770 nm). It has many useful properties for comparing colours of both luminous and non-luminous materials.
CIE 1976 L*a*b* Color Space
A uniform-color space utilizing an Adams-Nickerson cube root formula, suggested in 1976 for adoption by the CIE in 1976 for use in measurement of small color differences.
CIE Chromaticity Coordinates (Trichromatic Coefficients)
The ratios of each of the tristimulus values of a color to the sum of the tristimulus values. In the CIE system they are designated by x, y and z.
CIE Luminosity Function
A plot of the relative magnitude of the visual response as a function of wavelength from about 380 nm to 770 nm, adopted by CIE in 1924.
CIE Standard Observer
A hypothetical observer having the tristimulus color-mixture data recommended in 1931 by the CIE for a 2° field of vision (x, y, z or x2, y2, z2). A supplementary observer for a larger 10° field (x10, y10, z10) was adopted in 1964.
CIE Tristimulus Values
The amounts of the three reference or matching stimuli required to give a match, with the color stimulus considered, in a given trichromatic system.
CIE, Commission Internationale de l'Eclairage
In English, the International Commission on Illumination; the main international organization concerned with color and color measurement.
Clarity
The characteristic of a transparent material whereby distinct images may be observed through it.
CMC
Color difference based on the CIELAB color scale which can automatically generate tolerances for perceptible or acceptable differences.
Color Attribute
A three-dimensional characteristic of the appearance of an object, light source or aperture. One dimension usually defines the lightness and the other two together define the chromaticity.
Color Constancy
Substantial invariance of object-color perceptions in the presence of changes in illumination or viewing conditions.
Color Difference
The magnitude and character of the difference between two object colors under specified conditions.
Color Measurement Scale
A system of specifying numerically the perceived attributes of color.
Color Perceived
The visual sensation produced by light of different wavelengths throughout the visible region of the spectrum. By such perception an observer may distinguish differences between two objects of the same size, shape, and structure.
Color Specifications
Tristimulus values, chromaticity coordinates and luminance value, or other color-scale values, used to designate a color numerically in a specified color system.
Colorimeter
Instrument which senses tristimulus values and converts them to chromaticity components of color.
Contrast Ratio
A measure of opacity; the ratio of the luminous reflectance of a specimen backed with black material of specified reflectance to the reflectance of the same specimen backed with white material of specified reflectance.
The CIE Standard Illuminant that represents a colour temperature of 6504K. This is the colour temperature most widely used in graphic arts industry viewing booths. See Kelvin (K).
Series of illuminant spectral power distribution curves based on measurements of natural daylight and recommended by the CIE in 1965. Values are defined for the wavelength region 300 to 830 nm. They are described in terms of the correlated colour temperature. The most important is D65 because of the closeness of its correlated colour temperature to that of illuminant C, 6774K. D75 bluer than D65 and D55 yellower than D65 are also used.
Delta Descriptor
A comparison of a sample to a standard in words. It is based on color difference data. When the selected color scale is L, a, b or L*a*b*, the delta descriptors are lighter/darker, redder/greener, or yellower/bluer. When the selected color scale is LCh, the descriptors are lighter/darker, less saturated/more saturated and less chromatic/more chromatic.
Diffuse Reflection
Process by which incident light is redirected over a range of angles from the surface on which it is incident.
Diffuse Transmission
Process by which incident light, while being transmitted through an object, is redirected or scattered over a range of angles.
The massive band of electromagnetic waves that pass through the air in different sizes, as measured by wavelength. Different wavelengths have different properties, but most are invisible — and some completely undetectable — to human beings. Only wavelengths that are between 380 and 780 nm are visible, producing light. Waves outside the visible spectrum include gamma rays, x-rays, microwaves and radio waves.
An object that emits light. Emission is usually caused by a chemical reaction, such as the burning gasses of the sun or the heated filament of a light bulb.
A glass tube filled with mercury gas and coated on its inner surface with phosphors. When the gas is charged with an electrical current, radiation is produced. This, in turn, energises the phosphors, causing them to glow.
attribute due to surface reflected light, at specular angle to illumination, responsible for thre degree to which reflected highlights or images of objects may be seen as superimposed on a surface. An additional parameter to consider when determining a colour standard, along with hue, value, chroma, the texture of a material and whether the material has metallic or pearlescent qualities. Gloss is an additional tolerance that may be specified in the Munsell Colour Tolerance Set. The general rule for evaluating the gloss of a colour sample is the higher the gloss unit, the darker the colour sample will appear. Conversely, the lower the gloss unit, the lighter a sample will appear. Gloss can be measured in gloss units, which are expressed using the angle of measurement and the gloss value (e.g. 60º gloss = 29.8). A 60º geometry is recommended by the American Society for Testing and Materials (ASTM) D523 standard for the general evaluation of gloss
An achromatic scale ranging from black through a series of successively lighter greys to white. Such a series may be made up of steps that appear to be equally distant from one another (such as the Munsell Value Scale), or it may be arranged according to some other criteria such as a geometric progression based on lightness. Such scales may be used to describe the relative amount of difference between two similar colours.
Haze
The scattering of light within or at the surface of a nearly clear specimen, responsible for cloudy appearance seen in transmission.
HitchStandards
Standards close in color to the specimens being measured. These are the same as transfer standards.
Hue
The attribute of color perception by means of which an object is judged to be red, yellow, green, blue or purple.
Illuminant
A table of spectral distribution as close as possible to that of the natural light source, usually daylight, to be duplicated.
Incandescent illumination, yellow-orange in colour, with a correlated colour temperature of 2856K. It is defined in the wavelength range of 380 nm to 830 nm.
Tungsten illumination that simulates average daylight, bluish in colour, with a correlated colour temperature of 6774K.
Daylight lluminants, defined from 300 nm to 830 nm (the UV portion 300 nm to 380 nm being necessary to correctly describe colours that contain fluorescent dyes or pigments). They are designated as D, with a subscript to describe the correlated colour temperature; D65 is the most commonly used, having a correlated colour temperature of 6504K, close to that of illuminant C. They are based on actual measurements of the spectral distribution of daylight.
A sphere manufactured or coated with a highly reflective material that diffuses light within it.
Instrument Standards
Secondary standards which are only used with a particular instrument for maintaining the calibration of the instrument.
Light
Electromagnetic radiation in the spectral range (approximately 380 nm to 780 nm) detectable by the normal human eye.
Light Source
That element in an instrument or in the visual observing situation that furnishes radiant energy in the form of light.
Lightness
Perception by which white objects are distinguished from gray objects and light objects from dark color objects.
Unit of measurement for colour temperature. The Kelvin scale starts from absolute zero, which is -273° Celsius.
Metamerism
The phenomenon whereby colors of specimens match when illuminated by light of one spectral composition despite differences in spectral reflectance of the specimens, and that consequently may not match in light of some other spectral composition.
Metamerism Index
A measure of the degree of metamerism. A general index of metamerism is derived from two metameric spectral distribution curves without regard to the illuminant. A special index of metamerism is specified to two different illuminants.
Munsell Color System
The color identification of a specimen by its Munsell hue, value and chroma as visually estimated by comparison with the Munsell Book of Color.
Nanometer (nm)
Unit of length equal to 10-9 of a meter.
Object Color
The aspect of the appearance of an object dependent upon the spectral composition of the incident light, the spectral reflectance or transmittance of the object, and the spectral response of an observer.
Observing Conditions
The geometric and spectral conditions of illuminating and viewing a specimen for visual or instrumental evaluation. In visual observations, the conditions include the surroundings and the state of adaptation of the observer.
Opacity
The degree to which a sheet or film obscures a pattern beneath it.
Opponent-Colors System
A color system based on Hering's opponent-colors theory which states that there are six independent color dimensions which are perceived by three opponent-color systems: black-white, red-green and yellow-blue.
Perception
The combination of different sensations and the utilization of past experience in recognizing the objects from which the stimulation comes.
Perfect Diffuse Reflector
An ideal uniform diffuser with zero absorbance and zero transmittance.
Perfect Diffuse Transmitter
An ideal uniform diffuser with zero absorbance and zero reflectance.
Polychromator
A device for isolating narrow portions of the spectrum by dispersing light into its component wavelengths.
Precision
The degree of agreement of repeated measurements of the same property.
Primary Light
Any one of three lights in terms of which a color is specified by giving the amounts required to duplicate it by additive combination.
Primary Standard
A standard whose calibration is determined by the measurement of parameters usually different from the parameter for which it will be used as a standard.
A form of energy consisting of the electromagnetic spectrum, which travels at 299,792 kilometers/second (186,206 miles/second) through a vacuum, and more slowly in denser media (air, water, glass, etc.). The nature of radiant energy is described by its wavelength or frequency, although it also behaves as distinct quanta (“corpuscular theoryâ€). The various types of energy may be transformed into other forms of energy (electrical, chemical, mechanical, atomic, thermal, radiant), but the energy itself cannot be destroyed.
Reflectance
The ratio of reflected to incident radiation.
Reflection
Process by which incident light leaves a surface or medium from the side on which it is incident.
Refraction
The bending of light rays as they pass from one medium into another having a different index of refraction.
Regular Transmittance
Process by which incident light is transmitted through an object in a rectilinear, straight-through manner, without diffusion.
Repeatability
The degree to which a single instrument gives the same reading on the same specimen.
Reproducibility
The agreement attainable between measurements performed by different instruments in different laboratories.
Restandardize
To set the top of the standardization scale only.
Saturation
The attribute of color perception that expresses the degree of departure from the gray of the same lightness.
Scattering
The process by which light passing through granular, fibrous or rough surface matter is redirected throughout a range of angles.
Secondary Standards
All standards other than primary standards.
Shade Sorting
The grouping together of similarly-colored materials so that the materials within each group may be used together in a finished product.
Spectrocolorimeter
Visible spectrum-sensing full-scanning or abridged spectrophotometer with either an integral microprocessor or a personal computer programmed to perform tristimulus integrations, normally with a broad bandpass of 10 nm to 20 nm.
Spectrophotometer
An instrument used for measuring the transmittance and/or reflectance of specimens as a function of wavelength.
Spectrum
Spatial arrangement of electromagnetic energy in order of wavelength. For visible radiation, the spectrum is a band of color produced by breaking white light into its component colors.
Specular
Having the qualities of a speculum or mirror; having a smooth reflecting surface.
Specular Reflectance
Process by which incident light is redirected at the specular angle, as from a mirror, without diffusion.
Standard
A reference against which instrumental measurements are made.
Standardization
Process by which a given method, procedure or protocol is made to conform to prescribed conditions. Standardization can only follow calibration.
Known spectral data established by the CIE for different types of light sources. When using tristimulus data to describe a colour, the illuminant must also be defined. These standard illuminants are used in place of actual measurements of the light source.
A hypothetical ideal observer having either the tristimulus colour-mixture data recommended in 1931 by the CIE for a 2º viewing angle or for a larger angle of 10º as adopted in 1964.
The spectral response characteristics of the average observer defined by the CIE. Two such sets of data are defined, the 1931 data for the 2º visual field and the 1964 data for the 10º visual field. By custom, the assumption is made that if the observer is not specified, the tristimulus data has been calculated for the 1931, or 2º field observer. The use of the 1964 data should be specified.
Cyan, magenta and yellow. Theoretically, all three subtractive primaries on white paper are 100% combined, black. When combined with different intensities, a scale is made up of different colors. When combining two primary colors at 100%, an additive primary color, red, green, or blue, is equivalent to:
100% cyan + 100% magenta = blue
100% cyan + 100% yellow = green
100% magenta + 100% yellow = red
Tolerance
Limits that determine how far a sample can deviate from a standard. Tolerances can be set for any color scale or index parameter.
Total Reflection
Diffuse plus specular reflection.
Total Transmission
Diffuse plus regular transmission.
Transfer Standards
Standards close to the color of the specimens being measured. These are the same as hitch standards.
Translucency
The property of a material by which a major portion of the transmitted light undergoes scattering.
Transmission
Process by which incident light is transmitted through an object.
Transparency
The property of a material by which a negligible portion of the transmitted light undergoes scattering.
Of, or consisting of, three stimuli; generally used to describe components of additive mixture required to evoke a particular colour sensation.
An instrument that measures colour in terms of tristimulus values for a standard illuminant.
Percentages of the components in a three-colour additive mixture necessary to match a colour; in the CIE system, they are designated as X, Y and Z. The illuminant and standard observer colour-matching functions used must be designated; if they are not, the assumption is made that the values are for the 1931 observer (2º field) and illuminant C. The values obtained depend on the method of integration used, the relationship of the nature of the sample and the instrument design used to measure the reflectance or transmittance. Tristimulus values are not, therefore, absolute values characteristic of a sample, but relative values dependent on the method used to obtain them. Approximations of CIE tristimulus values may be obtained from measurements made on a tristimulus colorimeter that gives measurements generally normalised to 100. These must then be normalised to equivalent CIE values. The filter measurements should be properly designated as R, G and B instead of X, Y and Z.
Uniform Color Scale
A color scale or color solid in which the differences between points correspond to the perceptual visual differences between the colors represented by these points.
Indicates the degree of lightness or darkness of a colour in relation to a neutral grey scale. The scale of value (or V, in the Munsell system of colour notation) ranges from 0 for pure black to 10 for pure white. The value scale is neutral or without hue.
Wavelength
The distance, measured along the line of propagation, between two points that are in phase or on adjacent waves. Wavelength distribution determines the color of light. Wavelengths of visible light range from about 380 nm to about 780 nm.
One of the three CIE tristimulus values; the red primary.
Spectral colour-matching functions of the CIE standard observer used for calculating the X tristimulus value.
One of the CIE chromaticity coordinates calculated as the fraction of the sum of the three tristimulus values attributable to the X value.
One of the three CIE tristimulus values, equal to the luminous reflectance or transmittance; the green primary.
Spectral colour-matching function of the CIE standard observer used for calculating Y tristimulus value.
One of the CIE chromaticity coordinates calculated as the fraction of the sum of the three tristimulus values, attributable to the Y value.
One of the three CIE tristimulus values; the blue primary.
Spectral colour-matching function of the CIE standard observer used for calculating the Z tristimulus value.
One of the CIE chromaticity coordinates calculated as the fraction of the sum of the three tristimulus values attributable to the Z primary.
This glossary draws on multiple sources, including "ASTM" color and appearance standards. We have also "borrowed" from our own resources and compiled a rich reference of color terminologies for your convenient consultation. Any errors are the responsibility of the author. We welcome your comments. Our intention is not to provide all the terms used in our field. Instead, we hope to cover most of the commonly used terms related to the daily use of color computers that you may encounter in the literature.
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