Two LED fittings can produce identical lumen output at the same colour temperature and look completely different in practice. The difference is CRI. A low-CRI source makes skin look grey, food look unappetising, and fabrics lose their vibrancy. A high-CRI source renders colours faithfully, making every surface look as the designer intended.
What CRI Measures
CRI (Colour Rendering Index) measures how accurately a light source reveals the true colours of objects compared to a reference illuminant. The scale runs from 0 to 100. A score of 100 means perfect colour rendering, identical to the reference source. The reference is incandescent light for sources below 5000K and daylight for sources above 5000K.
How CRI is Calculated
The standard CRI (Ra) averages the rendering scores across 8 test colour samples (R1 to R8). These are deliberately muted, pastel colours. R9 (saturated red) is reported separately because it is the hardest colour for LEDs to render accurately. High-quality architectural LEDs specify both Ra and R9 values. A fitting with Ra 90 but R9 below 50 will still render red fabrics, skin tones, and food poorly.
CRI Requirements by Application
General offices and corridors function acceptably at CRI 80. This is the minimum standard for occupied commercial spaces under EN 12464-1. Most budget LED panels and troffers deliver CRI 80.
Retail, hospitality, galleries, and healthcare need CRI 90 minimum. At this level, colours appear natural and fabrics, artwork, and skin tones render accurately. Premium retail environments and art galleries often specify CRI 95+ for critical merchandise display.
Residential lighting should target CRI 90+ for living spaces where comfort and atmosphere matter. Kitchens benefit from CRI 90+ for food preparation (fresh produce looks fresh, not grey). Bathrooms need CRI 90+ so skin tones render accurately in mirrors.
The R9 Factor
R9 measures saturated red rendering. Red is present in skin tones, wood finishes, brick, food, and many textiles. A fitting with CRI 80 might have R9 as low as zero. This means red objects appear dull and brown. For any application involving people, food, or natural materials, insist on R9 above 50. Premium specifications require R9 above 90.
CRI vs Lumen Output
Higher CRI generally costs lumens. The phosphor chemistry that improves colour rendering reduces overall luminous efficacy slightly. A CRI 80 chip might deliver 140 lumens per watt while the same chip at CRI 97 delivers 110 lumens per watt. The trade-off is worth it. Perceived brightness depends on colour quality, not raw lumen count. A 90 CRI space often feels brighter than an 80 CRI space at the same lux level because colours appear more vivid and surfaces more distinct.
TM-30: The Next Generation
CRI has limitations. It only tests 8 muted colours and averages the results, potentially masking weaknesses in specific hues. IES TM-30 provides a more comprehensive assessment using 99 colour evaluation samples. It reports two metrics: Rf (fidelity, similar to CRI Ra) and Rg (gamut, measuring saturation). TM-30 has not yet replaced CRI in mainstream specifications but forward-thinking manufacturers report both values.
Practical Specification Advice
Specify CRI 80 minimum for back-of-house, car parks, and plant rooms. Specify CRI 90 minimum for all occupied spaces, retail, hospitality, and healthcare. Specify CRI 95+ for art galleries, premium retail, and colour-critical environments. Always request R9 values alongside Ra. EMPRICS products display CRI and R9 data on every product page.