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A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A 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 colour A neutral colour, such as white, gray or black, that has no hue. Also termed nonchromatic. 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. Attribute Distinguishing characteristic of a sensation, perception or mode of appearance. Distinction is made between chromatic and geometric appearance attributes.

B Brightness The attribute of visual sensation by which an observer is made aware of differences in luminance.

C 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. Chromaticity That part of a colour specification which does not involve luminance. Cie, commission internationale de l In English, the International Commission on Illumination; the main international organization concerned with colour and colour measurement. Cie 1976 lab colour space A uniform-colour space utilizing an Adams-Nickerson cube root formula, suggested in 1976 for adoption by the CIE in 1976 for use in measurement of small colour differences. Cie chromaticity coordinates (trichromatic coefficients) The ratios of each of the tristimulus values of a colour 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 colour-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 colour stimulus considered, in a given trichromatic system. Clarity The characteristic of a transparent material whereby distinct images may be observed through it. Cmc Colour difference based on the CIELAB color scale which can automatically generate tolerances for perceptible or acceptable differences. Colorimeter Instrument which senses tristimulus values and converts them to chromaticity components of colour. Colour 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. Colour constancy Substantial invariance of object-colour perceptions in the presence of changes in illumination or viewing conditions. Colour difference The magnitude and character of the difference between two object colours under specified conditions. Colour measurement scale A system of specifying numerically the perceived attributes of colour. Colour 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.  Colour sensor Colour Sensor’s detect and report an objects colour. Depending on how advance the sensor is you may be able to transfer this data into an easy to understand colour scale such as Hunter L,A,B or CIE L,A,B Colour specifications Tristimulus values, chromaticity coordinates and luminance value, or other color-scale values, used to designate a colour numerically in a specified colour system. 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.

D Delta descriptor A comparison of a sample to a standard in words. It is based on colour difference data. When the selected colour scale is L, a, b or L*a*b*, the delta descriptors are lighter/darker, redder/greener, or yellower/bluer. When the selected colour scale is LCh, the descriptors are lighter/darker, less saturated/more saturated and less chromatic/more chromatic. Densitometer A densitometer is an instrument that measures the Optical density ( degree of darkness ) of a photographic or semitransparent material or of a reflecting surface. The densitometer is basically a light source aimed at a photoelectric cell. It determines the density of a sample placed between the light source and the photoelectric cell from differences in the readings. Modern densitometers have the same components, but also have electronic integrated circuitry for better reading. 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.

E None found.

F None found.

G None found.

H Haze The scattering of light within or at the surface of a nearly clear specimen, responsible for cloudy appearance seen in transmission. Hitch standards Standards close in colour to the specimens being measured. These are the same as transfer standards. For Further information on the meaning of this word or phrase and how it can relate to you please contact application@thinkstothard.com Hue The attribute of colour perception by means of which an object is judged to be red, yellow, green, blue or purple. Hunter l,a,b scale A uniform colour scale devised by Hunter in 1958 for use in a colour difference meter. It is based on Hering’s opponent-colours theory of vision.

I Illuminant A table of spectral distribution as close as possible to that of the natural light source, usually daylight, to be duplicated. Instrument standards Secondary standards which are only used with a particular instrument for maintaining the calibration of the instrument.

J None found.

K None found.

L 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.

M Metamerism The phenomenon whereby colours 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 colour system The colour identification of a specimen by its Munsell hue, value and chroma as visually estimated by comparison with the Munsell Book of Colour.

N Nanometer (nm) Unit of length equal to 10−9 of a meter.

O Object colour 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 colours system A colour system based on Hering’s opponent-colours theory which states that there are six independent color dimensions which are perceived by three opponent-colour systems: black-white, red-green and yellow-blue.

P Perception The combination of different sensations and the utilization of past experience in recognizing the objects from which the stimulation comes. Perfect diffuse reflector The combination of different sensations and the utilization of past experience in recognizing the objects from which the stimulation comes. 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 colour 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.

Q None found.

R 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.

S Saturation The attribute of colour 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-coloured 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 colour produced by breaking white light into its component colours 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.

T Tolerance Limits that determine how far a sample can deviate from a standard. Tolerances can be set for any colour scale or index parameter. Total reflection Diffuse plus specular reflection. Total transmission Diffuse plus regular transmission. Transfer standards Standards close to the colour 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. Turbidity Turbidity is the cloudiness or haziness of a fluid caused by individual particles (suspended solids) that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids can contain suspended solid matter consisting of particles of many different sizes. While some suspended material will be large enough and heavy enough to settle rapidly to the bottom of the container if a liquid sample is left to stand (the settable solids), very small particles will settle only very slowly or not at all if the sample is regularly agitated or the particles are colloidal. These small solid particles cause the liquid to appear turbid. Turbidity (or haze) is also applied to transparent solids such as glass or plastic. In plastic production haze is defined as the percentage of light that is deflected more than 2.5° from the incoming light direction. You can measure the Turbidity of a liquid or solid using a Spectrophotometer that can measure transmission. See our Benchtop > UltraScan VIS instrument for more information on a transmission instrument.

U Uniform colour scale A colour scale or colour solid in which the differences between points correspond to the perceptual visual differences between the colours represented by these points.

V None found.

W Wavelength The distance, measured along the line of propagation, between two points that are in phase or on adjacent waves. Wavelength distribution determines the colour of light. Wavelengths of visible light range from about 380 nm to about 780 nm.

X None found.

Y None found.

Z None found.

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