What is ANSI/IES TM-30-20 “Intent”?

ANSI/IES TM-30-20 “TECHNICAL MEMORANDUM: IES METHOD FOR EVALUATING LIGHT SOURCE COLOR RENDITION" introduces a new concept, Intent, in Annex E and F. Intent adds flexibility and is less prescriptive by using color rendition metrics focused on different end user applications of a light source. Instead of the familiar two valued CRI Ra, R9 style criteria, TM-30-20 Intent has three metrics and three levels of priority:

• Preference - subjective evaluations of pleasantness, naturalness, acceptability, and related qualities.
• Vividness - subjective evaluations of color vividness, vibrancy or saturation.
• Fidelity - objective quantification of color fidelity. Average color fidelity measures such as TM-30-18 Rf quantify the average color shift in comparison to a reference illuminant.

These definitions are shown in the table below using measurables found in the TM-30-18 report structure. For intent ratings below priority level 3, a minus sign is used (P-, V-, F-).

The figure below is a TM-30-18 report for a Luminus Hospitality™ part with a 2700 K CCT. Hospitality™ LEDs have warm CCTs with premium color rendering just on the bottom edge of the BBL to ensure there are never any green or pink tints.

P1, V3, F1

*This report format is still called TM-30-18

The values needed to assign intent ratings are labeled on the figure, and we have

• Fidelity Index, Rf = 95 (average color fidelity)
• Gamut Index, Rg = 103 (measure of average gamut areas for all hue bins)
• Local Chroma Shift in Hue Bin 1, Rcs,h1 = 0 (radial shift in the bin 1 vector)
• Local Color Fidelity in Hue Bin 1, Rf,h1 = 97 (average color fidelity in bin 1).

These values translate to a P1, V3, F1 intent rating which is an excellent result for an application like hospitality, museum, or retail lighting.

Rf and Rg are average color fidelity and gamut area measures, which consider separate aspects of color rendition. An increase or decrease in gamut area implies a reduction in color fidelity. The two values cannot be simultaneously maximized. The local chroma shift and local color fidelity measures consider hue bin 1 which is in the reddish region of the Color Vector Graphic.

An RGB LED light source with high vividness intent from the IES example database is shown below. This light source has intent ratings of P-, V1, and F-. The color point for this device is on the black body curve so it looks white. The red and green hues are oversaturated which makes them “pop” but the color fidelity and preference ratings suffer when the gamut values are maximized to this extent.

P-, V1, F-

Some other examples of Luminus products with premium color rendering are shown below.

AccuWhite™ the original flagship COB line since 2013 with 97-98 CRI typical and beautiful TM-30-20 values. This product is centered on the black body curve.

P1, V-, F2

Sensus™ below black body COBs are a retail lighting favorite for pure whites and vivid colors, without sacrificing efficacy. Xtreme Sensus takes you even further below the BBL for whiter whites and super-saturated colors.

P2, V-, F2

Smooth White™ with a broad, natural spectrum, is most similar to halogen but without dangerous near-UV like some other broad-spectrum LEDs might have.  With R values all >90, it’s our latest premium color rendering light source family with low blue content and rich, vibrant reds.

P1, V-, F1

Annex E, Figure E1, in TM-30-20 shows the general tradeoffs between achievable combinations of P, V, F ratings. The LEDs discussed above are marked on the figure below.

Note that if your intent is extremely high energy efficiency, you will need to use products with P-, V-, F- intent ratings. White LEDs with Ra values below 80 typically have minus fidelity ratings in this system but better lumens per watt compared to premium color fidelity LED products. This is a consequence of the poor eye response to red light. High CRI requires higher red content which decreases the lumens per watt of a white LED.

This is a red centric rating system similar to, but better than, using Ra, R9 specifications. Annex F in
TM-30-20 contains the underlying data and mathematics behind this improvement.

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