The latest test interface of ies tm-30-18 color quality evaluation method is as follows. This report is measured by integrating sphere spectrometer system.

 

 

 

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On May 18, 2015, the illuminating engineering society of North America (ies) officially released a new evaluation method of light source color rendering, ies tm-30-15 method for evaluating light source color rendering, which has been used for three years. On October 9, 2018, the North American Institute of lighting engineering (ies) released a new version of the standard for evaluating light source color rendering (ies tm-30-18 method for evaluating light source color rendering), updating the IES tm-30-15 standard.

 

 

 

Compared with ies tm-30-15, the tm-30-18 version has the following three modifications:

 

 

 

The spectral reflectance calculation function of the color plate in the range of less than 400 nm and more than 700 nm was adjusted

 

 

 

The transition region of the reference light source is adjusted, and the applicable color temperature range is changed from 4500 k-5500 K to 4000 k-5000 K

 

 

 

The evaluation formula of color fidelity RF was modified, and the calculated scale factor was changed from 7.54 to 6.73

 

 

 

In April 2017, CIE released a technical report CIE 224: 2017 color fidelity index for accurate scientific use, which defines the color fidelity index RF. The index is calculated based on the fidelity index in ies tm-30-15, but there are slight differences in the extrapolation method used for color evaluation samples, the transition region of the reference light source, and the scale factor for the fidelity calculation. With the release of tm-30-18, the two documents have been coordinated, which is an important step in the globalization of color fidelity measurement.

 

 

 

For a long time, the general color rendering index RA used by CIE to evaluate color quality has been widely used to describe the visual experience of various light source technologies. However, ies thinks that RA only considers one aspect of color quality, which can not fully express the human eye's perception of color, and can not establish the integrity of visual experience. It is defective in accurately reproducing the color of light source. To this end, ies established a color metrics task group in March 2013 to study the improvement measures to characterize the color rendering of light sources, so as to develop a system to replace CRI and better serve the lighting industry and its stakeholders. On May 18, 2015, ies officially released the normative document ies tm-30-15 for evaluating the color rendering performance of light sources. It uses two indicators, namely, the color fidelity index RF (Fidelity Index) and the color saturation index RG (gamut index), to evaluate the color quality, which is quite different from the CRI system of CIE.

 

 

 

Compared with CIE's original color rendering index evaluation system, the evaluation method of ies tm-30 has the following five major changes:

 

 

 

1. Double index evaluation system

 

 

 

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Color fidelity RF and color saturation RG of ies tm-30

 

 

 

Tm-30 uses fidelity RF and saturation RG to evaluate color quality. The fidelity RF is used to characterize the color rendering index CRI (color rendering index) of the light source, that is, the similarity of each standard color under the illumination of the test light source and that of the reference light source. The number ranges from 0 to 100, and the higher the value, the better the color authenticity. This index is similar to the general color rendering index RA in cie13.3-1995 to evaluate CRI, which is used to represent the average color fidelity. However, 99 new color samples and a newly developed calculation method are used in tm-30. Ies believes that RF can provide more representative and reliable data, and it will be more accurate in color reproduction.

 

 

 

RF = 100 is the maximum value, which means that there is no color difference with the natural light source, and the color effect is lifelike

 

 

 

RF = 0 is the minimum value, which means that the color difference with natural light source is the largest, and the color effect is distorted

 

 

 

The color saturation RG is used to represent the gamut index Gai (gamut area index), that is, the saturation degree of each standard color under the illumination of the test light source compared with the reference light source, and the index 100 represents the best saturation.

 

 

 

RG = 100 means that the saturation of the light source is the same as that of the natural light, and the color saturation is moderate

 

 

 

If RG > 100, it means that the light source can improve the color saturation, and the object looks more bright and energetic

 

 

 

If RG < 100, it means that the color saturation will decrease under the test light source, and the color saturation is insufficient, and the object becomes gray and dull

 

 

 

2. More and more realistic standard colors

 

 

 

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99 standard colors used in ies tm-30

 

 

 

CIE's RA selects eight Munsell color plates as standard colors. These colors have medium lightness and color saturation, which can fully represent the commonly used colors of indoor lighting, but they are not representative of colors with high saturation in outdoor lighting. Since the colors used are not enough to represent all visible wavelengths, lamp manufacturers can optimize the spectral power distribution (SPD) of their light sources to obtain higher measurement values.

 

 

 

Spectral reflectance distribution curve of 99 standard colors in ies tm-30.png

 

 

 

Spectral reflectance distribution curves of 99 standard colors in ies tm-30

 

 

 

Compared with RA with only eight standard color plates, The tm-30 system uses 99 standard color plates, which are no longer Munsell color cards, but are selected from 105000 colors of real objects, including natural objects, skin color, textiles, coatings, plastics, printing materials, color systems and other seven categories, representing the common colors from saturation to unsaturated, from light to dark in our life. The most important thing is that the 99 standard colors have the same sensitivity to each wavelength, so it is difficult for manufacturers to improve the measurement value by adjusting the spectral distribution.

 

 

 

Tm-30 gives spectral reflectometer of different color plate samples