CRI Explained: Why Ra 90+ Matters in Interiors and Restaurants
6 min reading time
CRI (Ra) measures how honestly a light source renders colour against daylight. Ra 80-89 is acceptable for back-of-house, Ra 90+ is the standard for homes and hospitality - and R9 above 50 is what makes food, skin and timber look alive. Plus what TM-30 adds.
In short: CRI (the colour rendering index, also written Ra) shows how faithfully a light source reproduces colour compared with daylight. The scale runs to 100. Ra 80–89 is acceptable in back-of-house and technical areas; Ra 90+ is the working standard for homes, restaurants and retail. But the number most people never check is R9 — deep red — and it is R9 that decides whether food looks appetising, skin looks healthy and timber looks expensive. This article goes into colour rendering specifically; for how CRI sits alongside IP, UGR and lumens on a datasheet see how to read a spec sheet, and for brightness targets by room see the lighting levels guide.
What CRI measures
CRI compares how a source renders a set of reference colour samples against a reference illuminant of the same colour temperature — a blackbody radiator below 5000 K, daylight above it. The closer the match, the higher the score. Crucially it is a measure of fidelity, not of quality or of brightness: a source can be perfectly faithful and still be dim, glary or the wrong colour temperature for the room.
The Ra scale
Ra 100 — the reference: natural daylight or an incandescent source
Ra 90+ — the standard for residential and premium interiors; international practice and EN 12464 targets treat this as the benchmark wherever appearance matters
Ra 80–89 — acceptable for corridors, plant rooms and back-of-house
Below Ra 80 — colours go grey and distorted; not acceptable in any occupied space
Ra 95+ — specialist: fitting rooms, art, cosmetics, colour-critical work
Why R9 is the number that matters
General Ra is the average of just eight desaturated pastel samples, R1 to R8. Saturated red is not among them — it is measured separately as R9, and it is not included in the headline figure. This is the single biggest blind spot in lighting specification.
R9 governs how food, skin tone and the depth of timber and leather appear
Specify Ra 90+ and R9 above 50; for restaurants and fitting rooms push R9 above 60
A source can post a respectable Ra 90 with R9 near zero — the average hides it completely
Cheap white LED chips are the usual offenders: red output is the expensive part of the spectrum
What TM-30 adds. The newer IES TM-30 method uses 99 colour samples and reports two figures: Rf (fidelity, comparable in spirit to Ra) and Rg (gamut — whether the source saturates or dulls colours overall). It is a better description of what your eye actually sees, and serious manufacturers now publish it. If a datasheet offers Rf and Rg alongside Ra, read those; if it offers neither R9 nor TM-30 data, treat the omission as an answer.
Where colour rendering is critical
Kitchen and dining
Colour rendering decides how raw ingredients and finished dishes look. With low R9, meat, fruit and anything red reads grey and stale — which is why a restaurant with beautiful food photography and cheap downlights gets complaints it cannot explain.
Appetising food and produce
High R9 is non-negotiable
Ra 90+ across the worktop and the table
In tropical hospitality this compounds with another problem: bright ambient daylight through glass sets your eye's white balance, so a low-CRI fitting looks far worse at lunch than it does at dinner. Test the kitchen and pass lighting at midday, not after dark.
Wardrobe and mirror
Here people judge fabric shades and make-up, so the light has to be close to daylight and honest about colour.
Accurate fabric and cosmetic tones
Ra 90+ at the mirror, ideally Ra 95
No shift in skin tone — which means matching CRI and colour temperature between the mirror lights and the room
Timber, stone and art
Natural materials and artwork only come alive under faithful colour rendering; otherwise textures read flat and dull.
The depth of timber and the figure in stone
Accent lighting on paintings and objects
Feature zones and display cases
In a premium interior CRI is precisely what separates an expensive-looking image from a flat one. You can spend heavily on marble and walnut and then erase both with a poor light source.
How to specify without getting caught
Three numbers, taken together
Colour rendering — Ra 90+ and R9 50+
Colour temperature — 2700–3000 K for homes and hospitality, 3500–4000 K for task areas
Illuminance — enough lumens on the working plane; brightness and fidelity are independent
Add a fourth if the room has screens or workstations: UGR ≤ 19 for glare control.
Common mistakes
Choosing on lumens alone and ignoring CRI entirely
Trusting the averaged Ra without checking R9 or TM-30
Cheap strip and lamps below Ra 80 hidden in coves, where you cannot see the source but you can see what it does to the wall
Mixing CRI within one zone — the most visible error of all. Two fittings on the same wall at Ra 95 and Ra 82 make the cheaper one look broken
Assuming CRI holds over time — poor-quality LEDs shift colour as they age, and heat plus humidity accelerate it
Practical rule: Ra 90+ and R9 50+ for living spaces and premium zones; in kitchens, at mirrors and over restaurant tables treat it as mandatory rather than a preference.
FAQ
What is CRI (Ra)? The colour rendering index: how faithfully a source shows colour compared with a daylight reference. The scale runs to 100 — higher means more natural colour.
What CRI do I need at home? Ra 90+ for living and premium interiors, with R9 above 50. Below Ra 80 colours look grey and distorted.
What is R9? A separate index for saturated red, excluded from the general Ra average. It governs how food, skin tone and the depth of timber appear — which is why a high Ra with a low R9 still looks lifeless.
Does CRI affect brightness? No. Brightness is lumens; CRI is colour fidelity. You can hit every lux target and still get a dull-looking room if the CRI is low.
What is TM-30, and should I ask for it? A newer method using 99 samples that reports Rf (fidelity) and Rg (gamut). It describes real appearance better than a single Ra number. Ask for it — serious manufacturers publish it.
How do I check a fitting's CRI? It is stated on the packaging or datasheet, as Ra and sometimes R9. If neither figure is published, that absence is itself a quality signal.
Need lighting that renders colour honestly?
RODESIGNE designs & manufactures custom lighting for villas, hotels and restaurants — Phuket & worldwide. We specify Ra 90+ with verified R9 across every fitting in a scheme, so nothing on the wall looks like the cheap one.
