GB/T 5702-2019Method of measuring the color rendering properties of light sources (English PDF)

3.1 Colour rendering of a light source

The influence of the light source spectrum on the colour appearance of the object.

This influence is caused by the observer intentionally or unintentionally comparing it with the colour appearance under the reference illuminator.

5.1 Spectroradiometer performance requirements

5.1.1 The wavelength range of the spectroradiometer shall be 380nm~780nm.

5.1.4 The detector shall work within the linear range.

5.1.5 The measurement light repeatability of the spectroradiometer shall be better than 1%.

5.3 Laboratory test conditions

5.3.1 The ambient temperature shall be (23±2) °C, and the relative humidity of the environment shall be no greater than 65%.

5.3.2 The light source to be measured shall be tested under rated conditions, and the power supply equipment shall comply with the following provisions.

5.3.3 Before measuring the colour rendering of the light source, the light source shall be preheated.

5.3.4 The test site shall be free of ambient light that affects the test results.

6.1 Calculation process of light source colour rendering

The calculation shall be carried out according to the calculation process specified in Figure 1.

6.2 Determination of reference illuminator

6.2.1 The correlated colour temperature of the light source to be measured shall be calculated according to GB/T 7922.

6.2.2 The colour temperature of the reference illuminator or correlated colour temperature shall be the same as the light source to be measured; and the spectral power distribution of the reference illuminator shall be calculated according to Formula (1).

6.2.3 The chromaticity difference between the light source to be measured and the reference illuminator shall be calculated according to Formula (8).

6.3 Calculation of colorimetric parameters

6.3.2 u, v chromaticity coordinates shall be calculated as per the Formulas (16) and (17).

6.4 Calculation of colour rendering

6.4.1 The colour difference delta E of the colour sample irradiated by the light source to be measured and reference illuminator shall be calculated by Formula (25).

6.4.2 The special colour rendering index Ri corresponding to each colour sample shall be calculated by Formula (26).

6.4.3 The general colour rendering index Ra shall be calculated by Formula (27) according to the special colour rendering index of No.1~No.8 standard colour samples specified in Appendix B.

A.1 The necessity of supplementary evaluation index

Colour rendering index is an evaluation method based on the influence of light source on colour fidelity. However, this method does not reflect the influence of factors such as the increase in saturation caused by the colour difference of the colour sample caused by the light source on human perception.

A.2 Calculation of the gamut area index of the light source

A.2.1 The colour gamut of the light source shall be calculated by Formula (A.1) according to the standard colour samples specified in Table B.1; U*, V* shall be calculated according to 6.3.

A.2.2 The colour gamut index Ga of light source to be measured can be calculated according to Formula (A.2).

A.3 Calculation of chromaticity index of the light source

A.3.1 The chromaticity index of the light source can be calculated based on the standard colour samples specified in Appendix B or the non-standard colour samples determined by the user.

A.3.2 The chromaticity C *k,i of the colour sample irradiated by the reference illuminator shall be determined according to the provisions of 5.2 of GB/T 7921-2008 as per the tristimulus values of Xi, Yi and Zi calculated in accordance with provisions of 6.3.1. […]