TM-30-20 Reinvents Color Rendering in Lighting Design

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In the case of lighting design, colour rendering can significantly impression the general aesthetic and performance of an area. The power of a light-weight supply to precisely reveal the colours of objects it lights is crucial, whether or not it’s for retail shows, museum displays or residential houses. 

Historically, the Colour Rendering Index (CRI) has been used as the usual for measuring colour rendering accuracy. Nonetheless, with the emergence of latest lighting applied sciences, similar to LEDs, demand for a extra complete and correct analysis methodology arose. This led to the event of ANSI/IES TM-30-20, a revolutionary method to assessing colour rendition in lighting.

Understanding CRI and Its Limitations

The Colour Rendering Index (CRI) was developed within the Seventies primarily based on the 1931 strategy of colorimetry.[1] Colour rendering refers back to the means of a light-weight supply to precisely characterize the colours of objects as they would seem underneath a reference gentle supply, daylight, incandescent, fluorescent, halogen or LED lamps. 

Lights with poor colour rendering could make colours seem uninteresting or muddy

Whereas CRI has served as a useful gizmo for a few years, it has a number of limitations. The eight-color palette utilized in CRI doesn’t totally characterize the huge vary of colours current in actual life. This turns into obvious when evaluating gentle sources that excel in rendering the reference colours however carry out poorly in precisely rendering different saturated colours. Moreover, CRI doesn’t account for colour temperature, making it difficult to match gentle sources with totally different spectral traits.

The Rise of TM-30-15: A Extra Complete Method

To deal with the constraints of CRI and supply a fuller analysis of colour rendering, the Illuminating Engineering Society (IES) launched TM-30-15 in 2015.[2] The brand new methodology presents a extra intensive palette of 99 colours. Moreover, TM-30-15 measures colour constancy, gamut and colour vector graphics.

A graphic showing the color palette used in TM-30-15 versus the 8 and 15 colors of the standard and extended CRI palettes respectively
TM-30-15 measures colour rendering accuracy utilizing 99 colours, a major growth even over the palette of 15 colours in prolonged CRI.

Colour Constancy Index (Rf)

The Colour Constancy Index (Rf) is likely one of the key metrics in TM-30-15. Just like CRI, it measures the common colour rendering efficiency of a light-weight supply. Nonetheless, in contrast to CRI, which makes use of eight pastel colours, Rf in TM-30-15 assesses colour constancy throughout 99 totally different colours. A better Rf rating signifies higher colour accuracy, with an ideal rating of 100 representing a light-weight supply that renders colours identically to the reference supply.

Gamut Index (Rg)

The Gamut Index (Rg) measures the saturation of colours rendered by a light-weight supply in comparison with a reference supply. It offers helpful details about the depth and vibrancy of colours. A better Rg rating signifies greater colour saturation, whereas decrease scores recommend undersaturation. The Gamut Index enhances the Colour Constancy Index by capturing the vividness and depth of colours.

Colour Vector Graphics

Whereas Rf and Rg present numerical scores, Colour Vector Graphics presents a visible illustration of colour saturation anomalies. This round vector graph overlays a colour area, indicating the place the sunshine supply could deviate from the reference supply by way of colour saturation. By visualizing the particular colour areas affected by saturation discrepancies, designers could make extra knowledgeable choices about using gentle sources in several functions.

The Developments of TM-30-20: A Additional Refinement

Constructing upon the muse of TM-30-15, the IES launched an up to date model, TM-30-20, which presents enhancements and refinements to the analysis methodology to offer a extra complete and correct evaluation of colour rendering. 

It makes use of a wider palette of 99 reference colours, chosen from real-world objects, to guage the colour constancy and saturation of a light-weight supply. Utilizing the most recent analysis findings and developments, it presents improved calculations and higher alignment with subjective visible outcomes. The updated standard offers specifiers with extra correct and dependable info for choosing gentle sources that meet their particular design intents and priorities. 

TM-30-20 takes into consideration your complete spectrum of sunshine emitted by LEDs, making it an acceptable methodology for evaluating the colour rendering capabilities of contemporary sources. 

Improved color rendering accuracy with the TM-30-20 method ensures patrons can view art as intended in galleries
Bettering colour rendering accuracy in artwork galleries ensures patrons view artwork because the artists meant.

Visualizing Colour Rendering with TM-30-20

To additional support in understanding the colour rendering traits of a light-weight supply, TM-30-20 offers two highly effective visible instruments: the Colour Vector Graph and the Gamut Index.

The Colour Vector Graph is a round illustration superimposed on a colour area, revealing any anomalies in colour saturation brought on by the sunshine supply. It exhibits particular areas of the colour spectrum that could be over or undersaturated, offering helpful insights for designers and specifiers. This graph helps determine potential points and permits for focused changes to attain the specified colour rendering.

The Gamut Index measures the complete vary of colour saturation underneath a selected gentle supply in comparison with pure daylight. A rating of 100 signifies that the colours rendered by the sunshine supply are equivalent to these underneath pure daylight. Scores beneath 100 recommend undersaturation, whereas scores above 100 point out oversaturation. The Gamut Index accordingly helps designers consider the general colour depth and modify lighting options.

Using TM-30-20 in Lighting Design

With a stable understanding of TM-30-20 and its key metrics,  you possibly can successfully use this methodology in sensible lighting design functions.

A graphic generated using the IES online spectral calculator showing the color rendering accuracy of an LED hybrid bulb.
Graphic generated utilizing the IES online spectral calculator, in conformance with the ANSI/IES TM-30-20 normal revealed by the IES.

1. Specifying Colour Rendering Necessities

TM-30-20 presents a complete set of really useful specification standards that may be utilized in varied lighting design eventualities. The specification standards are primarily based on three design intents: 

  • Desire
  • Vividness
  • Constancy 

Every design intent has three precedence ranges, permitting specifiers to fine-tune their necessities primarily based on the particular wants of a challenge.

Design Intent: Desire

The Desire design intent focuses on subjective evaluations of pleasantness, naturalness and acceptability of colour rendering. This design intent is especially related in retail, workplace, hospitality and residential lighting functions. TM-30-20 offers specification standards for 3 precedence ranges inside the Desire design intent, starting from strict necessities to extra versatile ranges.

Design Intent: Vividness

The Vividness design intent facilities round subjective evaluations of colour vividness, saturation and vibrancy. This design intent is commonly essential in leisure, show and retail functions. TM-30-20 presents specification standards for 3 precedence ranges inside the Vividness design intent, permitting specifiers to pick gentle sources that improve colour vividness whereas contemplating potential hue distortions.

Design Intent: Constancy

The Constancy design intent focuses on attaining a excessive match between a take a look at gentle supply and its reference. This design intent is crucial in functions like healthcare and colour matching, the place colour accuracy is of utmost significance. TM-30-20 offers specification standards for 3 precedence ranges inside the Constancy design intent, making certain consistency and minimizing colour shifts.

2. Understanding Precedence Ranges

TM-30-20 introduces precedence ranges inside every design intent to offer additional customization and adaptability. These precedence ranges permit designers to fine-tune their specs primarily based on the particular necessities of a challenge.

Precedence Degree 1 has the strictest necessities, making certain the very best degree of colour accuracy or saturation. Nonetheless, it might restrict the obtainable collection of gentle sources. Precedence Degree 3, then again, permits for variability in colour rendering efficiency however nonetheless meets the final intent. Designers should fastidiously consider the challenge’s wants and choose the suitable precedence degree.

3. Evaluating Mild Sources

When evaluating gentle sources utilizing TM-30-20, it’s essential to contemplate each the Rf and Rg metrics, together with the Colour Vector Graph and Gamut Index. These metrics present a complete understanding of colour rendering efficiency and permit for knowledgeable decision-making.

By analyzing the Colour Vector Graph, designers can determine any particular colour areas which will require adjustment or enchancment. The Gamut Index helps assess the general colour saturation and depth, making certain that the lighting answer aligns with the specified visible impression.

Correct colour rendering in retail shops permits vibrant merchandise to face out and enhances the client expertise.

4. Collaborating with Producers

As TM-30-20 positive aspects wider adoption, it’s important for designers to collaborate with lighting producers to make sure the provision of sunshine sources that meet the required colour rendering necessities. Producers can leverage the insights offered by TM-30-20 to develop and market merchandise that align with totally different design intents and precedence ranges.

By carefully working with producers, designers can entry a wider vary of lighting choices that ship the specified colour rendering qualities and improve the general lighting design.


With the introduction of TM-30-20, the lighting business has made progress in colour rendering analysis by offering a extra complete and correct methodology for evaluating colour constancy and saturation. With its key metrics, visible instruments, and customizable design intents, TM-30-20 presents designers the flexibility to tailor lighting options to particular challenge necessities. By embracing this revolutionary method, designers can elevate the visible expertise, enhance aesthetics and create lighting environments that showcase the fantastic thing about colour.


[1] Guide to Light and Color in Retail Merchandising. (2010). Help Recommends…, 8(1), 4–13.
[2] Illuminating Engineering Society. (2020). (tech.). Technical Memorandum: IES Methodology for Evaluating Mild Supply Colour Rendition (pp. 1–58). New York, NY. 
[3] Livingston, J., Royer, M., & Esposito, T. (2022, April 4). Using TM-30 to improve your lighting design. Illuminating Engineering Society.  
[4] Rea, M. S., & Freyssinier, J. P. (2010). Colour rendering: Past Satisfaction and Prejudice. Color Research & Application, 35(6), 401–409.  
[5] Royer, M., & Houser, Ok. (2015a). Textual content-alternative model: Understanding and applying TM-30-15.  

Royer, M., & Houser, Ok. (2015). Understanding and making use of TM-30-15 – Division of Power. Understanding and Applying TM-30-15 Webinar.

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