Joint ISO/CIE Standard
ISO 10526:1999/CIE S005/E-1998
CIE Standard Illuminants for Colorimetry

This joint ISO/CIE Standard specifies two illuminants for use in colorimetry:

CIE standard illuminant A
This is intended to represent typical, domestic, tungsten-filament lighting. Its relative spectral power distribution is that of a Planckian radiator at a temperature of approximately 2 856 K. CIE standard illuminant A should be used in all applications of colorimetry involving the use of incandescent lighting, unless there are specific reasons for using a different illuminant.

The standard recommends laboratory realizations of the CIE standard illuminant A.

CIE standard illuminant D65
This is intended to represent average daylight and has a correlated colour temperature of approximately 6 500 K. CIE standard illuminant D65 should be used in all colorimetric calculations requiring representative daylight, unless there are specific reasons for using a different illuminant. Variations in the relative spectral power distribution of daylight are known to occur, particularly in the ultraviolet spectral region, as a function of season, time of day, and geographic location. However, CIE standard illuminant D65 should be used pending the availability of additional information on these variations.

Values for the relative spectral power distribution of CIE standard illuminants A and D65 are given in Table 1 of this International Standard, with an accuracy of six significant digits. Values are given at 1 nm intervals from 300 nm to 830 nm.

This Standard has been approved by CIE, and by ISO as a joint ISO/CIE standard.
This Standard may be obtained from the CIE National Committees or the Central Bureau of the CIE. A French and a German version (ISO 10526:1999/CIE S 005/F-1998 and CIE S 005/G-1998) are also available.

The following TC members took part in the preparation of this standard:

J.J. Hsia, USA

K.D. Mielenz, USA (Chairman)

J.R. Moore, Great Britain
A.R. Robertson, Canada

H. Terstiege, Germany

J.F. Verrill, Great Britain