ISO 5631-3:2015 紙とボード—拡散反射による色の決定—パート3：屋内照明条件（D50 / 2度） | ページ 6

3.1

radiance factor

β

ratio of the radiance of a surface element of a body in the direction delimited by a given cone, with its apex at the surface element, to that of the perfect reflecting diffuser under the same conditions of illumination

Note 1 to entry: For fluorescent (luminescent) materials, the total radiance factor, β, is the sum of two portions, the reflected radiance factor, β_R , and the luminescent radiance factor, β_L , so that β = β_R + β_L .For non-fluorescent materials, the reflected radiance factor, β_R , is numerically equal to the reflectance factor, R.

3.2

intrinsic radiance factor

β_∞

radiance factor of a layer or pad of material thick enough to be opaque, such that increasing the thickness of the pad by doubling the number of sheets results in no change in the measured radiance factor

Note 1 to entry: The intrinsic radiance factor is often expressed as a percentage.

3.3

reflectance factor

R

ratio of the radiation reflected by a surface element of a body in the direction delimited by a given cone, with its apex at the surface element to that of the perfect reflecting diffuser under the same conditions of illumination

Note 1 to entry: The ratio is often expressed as a percentage.

Note 2 to entry: The reflectance factor is influenced by the backing if the body is translucent.

3.4

intrinsic reflectance factor

R_∞

reflectance factor of a layer or pad of material thick enough to be opaque, such that increasing the thickness of the pad by doubling the number of sheets results in no change in the measured reflectance factor

Note 1 to entry: The reflectance factor of a non-opaque sheet is dependent on the background and is not a material property.

3.5

tristimulus values

X, Y, Z

amount of the three reference colour stimuli, in a given chromatic system, required to match the stimulus considered

Note 1 to entry: In this part of ISO 5631, the CIE illuminant D50 and the CIE 1931 (2°) standard observer are used to define the trichromatic system.

Note 2 to entry: No subscript is applied to conform to the CIE convention that tristimulus values have no subscript when the CIE 1931 (2°) standard observer is used [the subscript 10 is applied for tristimulus values that are obtained using the CIE 1964 (10°) standard observer].

3.6

CIELAB colour space

three-dimensional, approximately uniform colour space, produced by plotting, in rectangular coordinates L*, a*, b*, quantities defined by the formulae given in Clause 9

Note 1 to entry: The quantity, L*, is a measure of the lightness of the test piece, where L* = 0 corresponds to black and L* = 100 is defined by the perfect reflecting diffuser. Visually, the quantities a* and b* represent respectively the red-green and yellow-blue axes in colour space, such that +a*is a measure of the degree of redness of the test piece, −a*is a measure of the degree of greenness of the test piece, +b*is a measure of the degree of yellowness of the test piece, and −b*is a measure of the degree of blueness of the test piece.If both a* and b* are equal to zero, the test piece is achromatic.