Guide to ANSI/IES TM-30-20
The lighting industry is constantly evolving, with new standards and technologies continuously emerging to improve the quality and efficiency of lighting systems. One of the standards that has received significant attention is ANSI/IES TM-30-20. Developed by the American National Standards Institute (ANSI) and the Illuminating Engineering Society (IES), TM-30-20 provides a comprehensive method for evaluating the color rendering of light sources. This method offers a more accurate and detailed analysis compared to previous standards.
ANSI/IES TM-30-20, officially called "IES Method for Evaluating Color Rendering of Light Sources", is a technical standard that offers a systematic approach to evaluating the color rendering properties of light sources.
Unlike previous standards such as the Color Rendering Index (CRI), which provided a single numerical value to represent color rendering, the TM-30-20 offers a more thorough evaluation by considering two key factors:
Fidelity Index (Rf): This measurement assesses how accurately a light source reproduces the colors of objects compared to a reference light. Rf values range from 0 to 100, with higher values indicating better color rendering.
Gamut Index (Rg): The gamut index evaluates the saturation of colors rendered by a light source compared to the reference lighting. Like Rf, Rg values also range from 0 to 100, with higher values indicating a more vibrant color palette.
The main differences between ANSI/IES TM-30-20 and Color Rendering Index (CRI) lie in their methodologies, scope and how comprehensively they evaluate color rendering. Here are the main differences:
Sample sets and color spaces:
The CRI method uses a limited set of eight pastel colors, which may not adequately represent the full spectrum of colors encountered in real-world applications.
The TM-30-20 uses a larger and more diverse set of 99 color evaluation samples that cover a wider range of hue, saturation and lightness. This wider sample set provides a more comprehensive evaluation of color reproduction.
Metrics:
CRI provides a single numerical value (Ra) to represent the overall color rendering ability of a light source. However, this single value cannot always capture all the nuances of color rendering.
The TM-30-20 introduces two main metrics: Fidelity Index (Rf) and Gamut Index (Rg). Rf measures the accuracy of color reproduction in relation to a reference light, while Rg assesses color saturation and color vibrancy. This dual-metric approach provides a more detailed and meaningful evaluation of color rendering.
Evaluation of Color Fidelity and Gamut:
CRI gives a general indication of color rendering quality, but does not distinguish between how accurately colors are reproduced and how many colors are reproduced. As a result, two light sources with the same CRI value can reproduce colors differently in terms of accuracy and saturation.
The TM-30-20 separately evaluates color fidelity (Rf) and gamut (Rg), providing more detailed information about how a light source renders colors compared to a reference light. This enables a more nuanced assessment of color rendering that takes into account both accuracy and saturation.
Color temperature dependency:
CRI values are calculated at a single reference color temperature (usually 2856 K for incandescent lamps and 6500 K for daylight).
The TM-30-20 can evaluate color rendering performance across a range of color temperatures, providing insight into how a light source's performance can vary under different lighting conditions.
Comparison between TM-30-20 and CRI:
To understand the benefits of TM-30-20 compared to older standards like Color Rendering Index (CRI), we can compare the two using a sample set of light sources with different parameters:
Conclusion:
In summary, the TM-30-20 offers a more comprehensive and accurate evaluation of color rendering compared to CRI. By incorporating a larger sample set, introducing separate metrics for fidelity and gamut, and considering variations across different color temperatures, TM-30-20 provides a more robust tool for selecting and designing lighting systems that accurately reproduce colors in different applications.