Understanding TM-30 and Its Relationship to CRI – What We Learned at the 2024 ALA Conference

The quality of your lighting can make a big difference in how a space feels and functions. At the recent American Lighting Association conference in West Palm Beach, one of my favorite breakout sessions was on the new TM-30 standard and how it compares to the traditional Color Rendering Index (CRI) measurement. Here’s what we learned and why TM-30 provides much more information about the quality of light rendered from a given source.

CRI Basics and Its Limitations:

• CRI, or Color Rendering Index, has been the most common way to measure how well a light source renders color. It uses a simple scale from 0 to 100—higher numbers mean colors look more accurate. Fun fact: The CRI standard was last updated in 1995, can you think of an important advancement in lighting since then?
• Limitations: CRI only looks at a small set of colors, ignoring many that are important, like deep reds. This can lead to misleading results, especially in spaces where color accuracy really matters.

What Is TM-30?

• TM-30 is a newer, more detailed way to measure how well light renders colors, and it’s now an official ANSI (American National Standards Institute) standard. This means it’s recognized as a reliable, comprehensive and regularly updated method for evaluating lighting quality.
• Unlike CRI, TM-30 uses 99 different colors to get a fuller picture of how a light source affects the look of objects. It breaks down color rendering into two main components: Rf (Fidelity Index): Similar to CRI but more accurate because it considers more colors. It pays close attention to reds, a color that CRI often overlooks. Red is vital for things like food, skin tones, fabrics, and artwork to appear as natural and vibrant as possible. Rg (Gamut Index): This tells you if colors look more or less saturated (vivid) under light. An Rg of 100 means there’s no change, while numbers higher than 100 mean colors look more intense.

Why TM-30 Matters:

• TM-30 offers a more complete picture of how colors appear under a light source. Its focus on red tones (R9) is especially important because reds are important in making spaces feel warm and inviting. This was a key point in the TM-30 breakout session.
• Key Insight from the session: Jason Livingston (Studio T+L, LLC) highlighted that TM-30’s deeper color analysis makes it easier to choose the right light for different settings. Whether it's for a cozy home kitchen or a retail store where products need to pop, TM-30 provides a clearer understanding of how colors will truly look.

Understanding Color Vector Graphics:

• One key difference in utilizing TM-30 vs. CRI are the detailed color vector graphic charts. These CVG’s provide a visual representation of how a light source affects color. The graphic uses a circular chart to show any shifts in hue and saturation for different colors. For example, if reds are rendered too dim or overly saturated, the graphic will highlight these changes, allowing you to adjust your lighting choices accordingly.
• Insights from the breakout session: Jason pointed out that this graphic helps lighting designers quickly see if a light source will make colors appear more vivid, washed out, or true to life. It's a great tool to ensure that the lighting will enhance the colors in a room rather than distort them.

Should You Use TM-30 or CRI?

• CRI is still useful for quick reference because it’s easy to understand and widely used. However, it doesn’t capture the whole story, especially when it comes to hues of red.
• TM-30, now an official ANSI standard, goes further by offering a more thorough analysis of color quality, which is why it’s increasingly being recommended in lighting design.
• Session Takeaway: The general advice from the ALA breakout session was to use both metrics for now. CRI gives a basic overview, but TM-30 provides the detailed information needed for more refined lighting choices.

Where TM-30 Shines:

• In the Home: Using TM-30 helps ensure that the colors of your walls, furniture, decor, artwork and plants look natural and appealing.
• In Retail: Properly rendered reds and other colors can make skin-tones, clothing, products and foods look their best, enhancing the customer experience.

This ALA breakout session made it clear that TM-30 could be a game-changer for lighting design. While CRI is still helpful, TM-30's focus on a wider range of colors, especially reds, provides a more complete picture of how lighting affects a space. Adopting TM-30 in lighting design will allow designers to better predict how a given light source looks in a room, or even make the choice of lighting a design element unto itself.