Definition
CRI (Color Rendering Index, designated as Ra) is a quantitative measure of a light source's ability to reveal object colors faithfully compared to a natural reference source (daylight for CCT ≥5000K, blackbody radiator for CCT <5000K). Developed by the CIE (International Commission on Illumination), CRI ranges from 0 to 100 — a score of 100 means the source renders all eight standard test colors (R1-R8, low-saturation pastels) exactly as the reference would. However, CRI Ra alone is incomplete: it does not measure R9 (saturated red, critical for skin tones, food, and textiles) or R10-R15 (additional saturated colors). Modern LED evaluation increasingly uses TM-30-18 (Rf for fidelity, Rg for gamut) as a more comprehensive metric, but CRI Ra + R9 remains the industry standard for procurement specifications.
Key Data
| Parameter | Value / Explanation |
|---|---|
| CRI 95-100 | Excellent — museum, art gallery, surgical lighting. Color differences imperceptible. |
| CRI 90-95 | Very good — high-end retail, hospitality, healthcare, design studios |
| CRI 80-90 | Good — standard offices, schools, general commercial (EN 12464-1 minimum) |
| CRI 70-80 | Acceptable — warehouses, parking, outdoor area lighting where color is non-critical |
| CRI <70 | Poor — noticeable color distortion. Not recommended for occupied indoor spaces. |
| R9 (saturated red) | Critical supplemental metric. CRI 80 LED can have R9 near 0 — reds appear brown/gray. |
Application Guide
Museum & Gallery
CRI 95+, R9 >90, TM-30 Rf >90, Rg 95-105
Color accuracy is the primary purpose — artwork must look exactly as intended
Fashion retail
CRI 90+, R9 >80, 3000-4000K
Accurate red rendering critical for clothing, cosmetics, and skin tone perception
Office (general)
CRI ≥80, R9 recommended >20
EN 12464-1 minimum; CRI 80 sufficient for reading, typing, screen-based work
Conclusion & Procurement Recommendation
For B2B LED procurement, always specify CRI Ra minimum AND R9 minimum in RFQs. Many manufacturers advertise 'CRI 80' while R9 is near zero — reds, oranges, and skin tones will appear dull or brown. Key procurement requirements: (1) CRI Ra ≥90 AND R9 ≥50 for retail, hospitality, healthcare, (2) CRI Ra ≥80 AND R9 ≥20 for general office and education, (3) Request IES LM-79 test reports showing CRI Ra AND R1-R15 individual values, (4) For critical applications, also specify TM-30-18 Rf ≥85 and Rg 95-105 to avoid gamut distortion. Note: higher CRI LEDs are 15-30% less efficient — budget for more wattage to maintain target lux levels when upgrading from CRI 80 to CRI 90+.