What Is Color Rendering Index (CRI)?
As LED technology keeps advancing, lighting manufacturers offer more and more products with a high color rendering index, or CRI. Just as color temperature (CCT) changes how a room looks and feels, color rendering index determines how good the light actually looks once it lands on something. The two go hand in hand when you’re choosing lighting for an application.
So what is CRI? In short, it measures how a light source affects the appearance of color. It’s an assessment of how naturally a light shows the color of objects compared to a familiar reference, such as daylight.
The CRI scale gained popularity as LED lighting became common in homes. It’s measured from 0 to 100, and LED bulbs and fixtures at the higher end render the colors around them more accurately. That matters in museums and galleries, and it matters in an ordinary house too. Think about the daily tasks you do and how much the light quality affects them: applying makeup in a bathroom, studying in a home office, prepping food in a kitchen.
What Is a Good CRI?
At 0, colors are barely distinguishable from one another. At 100, you see an object’s true colors.
When this article was first published, most LED products landed between 80 and 90. That’s shifted. Today 90+ CRI is common across quality residential and commercial lines, and 95+ is widely available rather than a premium specialty item. As a rule, 90 or above is excellent, 80 to 90 is serviceable, and below 80 is low.
A useful way to think about it by application:
- CRI 80 and up: garages, storage, utility rooms, back of house, parking areas. Spaces where nobody is judging a color.
- CRI 90 and up: kitchens, bathrooms, living spaces, retail, hospitality, healthcare. Anywhere people look at food, finishes, merchandise or each other.
- CRI 95 and up: galleries, art display, premium retail, color critical work.
Worth knowing that higher CRI isn’t free. Pushing a product from 80 CRI to 90 CRI typically costs somewhere between 5% and 12% in efficacy, meaning fewer lumens per watt. That’s usually a trade worth making in a kitchen and usually not worth making in a warehouse.
There’s also a perceptual bonus that doesn’t show up in a lumen count. A 90 CRI space often reads as brighter than an 80 CRI space at the same measured light level, because colors look more distinct and surfaces separate from one another more clearly.
The Number CRI Doesn’t Tell You: R9
Here’s the part most CRI explanations skip, and it’s the single most useful thing to know when you’re comparing two fixtures.
The CRI figure on a spec sheet, properly called Ra, is an average of just eight test colors, R1 through R8. All eight are muted pastels. Saturated colors aren’t in the average at all.
R9 measures saturated red, and it’s reported separately. That matters because red is the hardest color for an LED phosphor to render well, and because red is doing a lot of work in the things people actually look at: skin tones, wood, meat, produce, brick, leather, fabric.
The practical consequence is that a fixture can advertise CRI 90 while its R9 sits near zero. The average still passes, but skin looks flat, steak looks gray and warm woods go lifeless. Two fixtures with identical CRI numbers can look completely different in a kitchen.
Targets worth asking for:
- R9 above 50 for general residential and commercial spaces.
- R9 above 80 for kitchens, art display, retail, hospitality and anywhere skin tones matter.
Quality LED products increasingly publish R9 alongside CRI, often in the 80 to 98 range on 90+ CRI products. If a spec sheet lists CRI but not R9, that omission is usually telling you something.
CRI and Color Temperature Are Not the Same Thing
CRI and color temperature measure two entirely different properties, and it’s easy to conflate them.
Color temperature is measured in Kelvin (K) and describes whether light appears warm or cool. CRI describes how accurately that light renders color. A 5000K daylight LED from one manufacturer might have a CRI of 75, while a 5000K lamp from another has a CRI of 90. Same apparent color of light, very different quality.
To learn more about color temperature and how it applies in your home, read Choosing the Right Color Temperature.
Pay attention to both CRI and color temperature when shopping. You want colors to be crisp and sharp so your decor, paint and furnishings look their best.
Beyond CRI: What Is TM-30?
CRI was developed in 1965, long before LEDs existed, and it was built around light sources that behave nothing like a modern LED. Its limitations are well documented: only eight pastel samples, all averaged together, with saturated colors left out.
The Illuminating Engineering Society developed TM-30 as a more complete method. The current version is ANSI/IES TM-30-24, and instead of eight pastels it evaluates a source against 99 real world color samples. It reports two numbers rather than one:
- Rf (fidelity): how accurately colors render, on a 0 to 100 scale. This is the direct successor to CRI.
- Rg (gamut): how saturated colors appear. Above 100 means colors look more vivid than the reference. Below 100 means they look muted.
Rg is the genuinely new information. CRI can only tell you how far off a color is, not which direction it went. A retail space often wants Rg slightly above 100 so merchandise looks vivid. An office usually wants Rg close to 100 so nothing looks artificially punched up.
Rough targets if you’re specifying with TM-30: offices and workplaces want Rf of 90 or better with Rg around 95 to 103. Retail and hospitality often benefit from Rg around 102 to 108.
TM-30 hasn’t replaced CRI in everyday specifications, and most bid documents still ask for “CRI ≥ 80” or “CRI ≥ 90.” So you can’t ignore CRI. But the better manufacturers now publish both, and when they do, the TM-30 data tells you considerably more.
How to Read a Spec Sheet
When you’re comparing two products, look for these in order:
- CRI (Ra) to set the baseline. 90+ for any occupied space.
- R9 to check the reds. If it isn’t published, ask.
- TM-30 Rf and Rg if the manufacturer reports them.
- SDCM for color consistency between fixtures. 3-step or tighter means two fixtures out of the same box will match on the ceiling.
- CCT last, since that’s a preference rather than a quality measure.
One thing spec sheets can’t tell you: how a source behaves in your actual room, over your actual finishes. On a large or color critical job, get a sample fixture up before you commit to a hundred of them.
Ask the PROs
Every LED product at PROLIGHTING has a specification section on its product page listing the light source’s properties. You’ll find the color rendering index, lumens, watts, color temperature, efficiency metrics and other lighting facts there. Choosing LED lighting with a higher CRI rating gets you more accurate color in your space.
Our team of certified lighting specialists can answer any CRI related questions. We have experience lighting every application and can help with product selection, project quotes and a custom lighting layout for your space. Our PROs are available by phone, email and live chat Monday through Friday, 8AM to 5PM EST.
Comments are closed.