Colour quality is the difference between a guest room that photographs well and one that looks tired in the online listing. This note explains what the metrics measure, which ones matter for skin tones and wood veneers, and how to write the requirement so suppliers cannot send you the cheapest compliant part.
What CRI does and does not tell you
CRI (colour rendering index, CIE 13.3) is the average of eight pastel test colours, R1–R8. It is a 1970s metric built around fluorescent sources. Two consequences matter for hospitality:
It ignores deep red. R9 is not part of the average, so a fitting can score Ra 85 while rendering skin, wood and wine poorly — precisely the colours a hotel is selling.
It hides hue shifts. A source can score well on average while making greens dull and reds orange. Guests read that as “cheap lighting” without being able to say why.
Add R9 and a minimum for it
R9 (saturated red) should be specified separately. For guest rooms and bathrooms, require R9 ≥ 50; for vanity and mirror lighting where skin tone is judged up close, R9 ≥ 70.
| Application | Ra | R9 | Note |
|---|---|---|---|
| Guest room general | ≥ 90 | ≥ 50 | Warm 2700–3000K, SDCM ≤ 3 |
| Vanity / mirror | ≥ 90 | ≥ 70 | Skin tone is the use case |
| Wardrobe interior | ≥ 80 | ≥ 20 | Colour matching of clothes matters |
| Corridor / cove | ≥ 80 | — | Evenness matters more than fidelity |
Values are specification targets, not test results for a specific model.
TM-30 is the modern check
TM-30 (IES TM-30-20) reports Rf (fidelity, 0–100, like an improved CRI) and Rg (gamut, 100 = neither oversaturated nor dull), plus a 16-point colour vector graphic. Ask for the graphic, not just the number: it shows whether reds are being pushed to flatter wood finishes, which is a deliberate design choice some hotel brands want.
Practical targets: Rf ≥ 90, Rg 98–104 for guest rooms. Rg below 95 looks flat; above 105 starts to look unnatural on skin.
Consistency between fittings is half the battle
Two fittings from the same batch with the same CRI can still look different if their colour points sit at opposite ends of a 5-step MacAdam ellipse. Specify SDCM ≤ 3 (3-step) for anything visible together in one room, and Duv within ±0.003 so nothing reads pink or green.
Also fix the CCT: 2700K for classic luxury, 3000K for contemporary, and do not mix them in one sight line — the eye detects a 200K difference between adjacent fixtures long before it detects a CRI difference.
Flicker is part of colour quality
A fitting can render colour perfectly and still make a room feel wrong, because flicker is perceived as discomfort rather than seen. Require Pst LM ≤ 1.0 and SVM ≤ 0.4 (EU 2019/2020 single lighting regulation limits), and ask for the dimming curve — flicker usually appears below 20% dim, exactly where a night-time hotel room sits.
Wording you can paste into a submittal
That paragraph costs nothing and eliminates most of the fittings that would have looked wrong six months after handover.
Specifier's checklist
- Ra and R9 specified separately (R9 ≥ 50, ≥ 70 for vanity)
- TM-30 Rf ≥ 90 and Rg 98–104, with the vector graphic submitted
- SDCM ≤ 3 and Duv ±0.003 for fittings visible together
- Flicker limits at both 100% and 20% dimming
- LM-79 report per CCT/CRI variant, not per product family
Questions we get asked
Is Ra 90 enough for a hotel guest room?
Do I need TM-30 if I already specify R9?
What about 2700K versus 3000K?
Can suppliers claim R9 without testing?
Send the furniture drawing. We will answer with a lighting solution.
Cut-out drawings, photometric files and samples for the lines that fit your detail.
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