GLOSSARY OF COLOUR TERMS

Glossary of Colour Terms

Abridged Spectrophotometer (VIS):

a spectrophotometer that uses a set of colour filters to define relatively broadband wavelength intervals in the visible spectrum.

Absorbance:

see Optical Density.

Absorption:

the transformation of radiant energy to a different form of energy by interaction.

Absorptance:

the ratio of absorbed radiant flux to the incident flux.

Brightness:

the quantity of light reflected (a bright colour reflects more light whereas a dim colour reflects less).

Chroma:

see Saturation.

Chromatic:

perceived as having a hue; not white, grey or black.

Chromaticity:

chromaticity is that part of a colour specification that does not involve the amount of light energy; it is specified by pairs of chromaticity co-ordinates or dominant wavelength and purity.

Chromaticity coordinates:

the ratio of each of the tristimulus values of a colour to the sum of the tristimulus values (designated x, y, z in the CIE system).

CIE, Commission Internationale de l’Eclairage:

the international organisation concerned with light, vision and colour.

Comparator:

an instrument that relies on a comparison between a coloured sample and a suitable range of colour standards under specified conditions.

Colorimeter:

an instrument which relies on a match between a coloured sample and a stimulus produced by mixing a suitable combination of one or more, of at least three, primaries.

Colour difference:

the magnitude of the difference between two object colours under specified conditions.

Colour grading:

identifying a sample by a colour grade or score which is specific to the colour or the material graded

Colour matching:

procedure for providing a trial colour which is indistinguishable, within a specified tolerance, from a reference colour

Colour measurement:

process of deriving, by visual or electronic means, a set of numbers that describe the attributes of a colour

Hue or colour:

the type of colour, whether it is red, blue, green or purple etc.

Optical density:

logarithm to the base 10 of the reciprocal of the transmittance.

Photometer:

an instrument that measures the relative amount of light transmitted by, or reflected from, a sample in a defined wavelength interval in the visible spectrum.

Saturation or chroma:

refers to the strength or amount of the hue - how much the full hue is desaturated with white.

Spectrophotometer (VIS):

an instrument that measures the relative amount of light transmitted by, or reflected from, a sample in a small wavelength interval at each wavelength in the visible spectrum.

Spectrophotometry:

measurement of the relative amounts of radiant flux at each wavelength of the spectrum.

Standard Illuminants:

relative spectral power distributions defining illuminants for use in colorimetric computations.

Transmission:

passage of radiation through a medium without change of frequency.

Transmittance:

the ratio of transmitted flux to incident flux under specified conditions.

Tristimulus Colorimeter:

an instrument with spectral response functions that are directly proportional to the colour matching functions of the CIE Standard Colorimetric Observer.

Tristimulus Values:

the amounts of three specified stimuli required to match a colour.

Turbidity:

reduction of transparency of a specimen due to the presence of particular matter.



			Glossary of Colour Terms Abridged Spectrophotometer (VIS): a spectrophotometer that uses a set of colour filters to define relatively broadband wavelength intervals in the visible spectrum. Absorbance: see Optical Density. Absorption: the transformation of radiant energy to a different form of energy by interaction. Absorptance: the ratio of absorbed radiant flux to the incident flux. Brightness: the quantity of light reflected (a bright colour reflects more light whereas a dim colour reflects less). Chroma: see Saturation. Chromatic: perceived as having a hue; not white, grey or black. Chromaticity: chromaticity is that part of a colour specification that does not involve the amount of light energy; it is specified by pairs of chromaticity co-ordinates or dominant wavelength and purity. Chromaticity coordinates: the ratio of each of the tristimulus values of a colour to the sum of the tristimulus values (designated x, y, z in the CIE system). CIE, Commission Internationale de l’Eclairage: the international organisation concerned with light, vision and colour. Comparator: an instrument that relies on a comparison between a coloured sample and a suitable range of colour standards under specified conditions. Colorimeter: an instrument which relies on a match between a coloured sample and a stimulus produced by mixing a suitable combination of one or more, of at least three, primaries. Colour difference: the magnitude of the difference between two object colours under specified conditions. Colour grading: identifying a sample by a colour grade or score which is specific to the colour or the material graded Colour matching: procedure for providing a trial colour which is indistinguishable, within a specified tolerance, from a reference colour Colour measurement: process of deriving, by visual or electronic means, a set of numbers that describe the attributes of a colour Hue or colour: the type of colour, whether it is red, blue, green or purple etc. Optical density: logarithm to the base 10 of the reciprocal of the transmittance. Photometer: an instrument that measures the relative amount of light transmitted by, or reflected from, a sample in a defined wavelength interval in the visible spectrum. Saturation or chroma: refers to the strength or amount of the hue - how much the full hue is desaturated with white. Spectrophotometer (VIS): an instrument that measures the relative amount of light transmitted by, or reflected from, a sample in a small wavelength interval at each wavelength in the visible spectrum. Spectrophotometry: measurement of the relative amounts of radiant flux at each wavelength of the spectrum. Standard Illuminants: relative spectral power distributions defining illuminants for use in colorimetric computations. Transmission: passage of radiation through a medium without change of frequency. Transmittance: the ratio of transmitted flux to incident flux under specified conditions. Tristimulus Colorimeter: an instrument with spectral response functions that are directly proportional to the colour matching functions of the CIE Standard Colorimetric Observer. Tristimulus Values: the amounts of three specified stimuli required to match a colour. Turbidity: reduction of transparency of a specimen due to the presence of particular matter.