CRI Comparison Tool
Color Rendering Index compares how colors appear under a test light source with how they appear under a reference illuminant of similar correlated color temperature. General CRI (Ra) is calculated from the first eight CIE test color samples; an Ra value of 100 indicates the closest agreement with the reference illuminant within the CRI method.
This tool explores what CRI can — and cannot — tell you about color rendering. Every example below is an actual spectral power distribution (SPD): all metrics and all swatch colors are calculated from the spectrum using the CIE 13.3-1995 method, never inferred from a CRI number.
For the full technical background on CRI, R9 and TM-30, see our High CRI LED Lighting Guide , or mix your own spectrum in the Spectrum Designer .
CRI is a summary fidelity metric. It does not uniquely define a spectrum and cannot fully predict saturation, hue shifts, or the appearance of specific materials. Two sources with the same Ra can render individual colors quite differently.
Explore example spectra
450 nm blue pump with a broad 540 nm phosphor and a moderate 625 nm red phosphor.
Spectral Power Distribution
Computed Metrics
All values are computed from the SPD with the CIE 13.3-1995 test-color method. The reference illuminant is a Planckian radiator at the source's correlated color temperature. R9 is a separate special color rendering index and cannot be reliably inferred from General CRI (Ra).
Special Color Rendering Indices R1–R14
CIE test color samples under this spectrum
Each swatch shows the CIE test color sample under the reference illuminant (left) and under this source's SPD (right), both computed from spectral data.
R1 — Light greyish red
R1 = 82
R2 — Dark greyish yellow
R2 = 84
R3 — Strong yellow-green
R3 = 83
R4 — Moderate yellowish green
R4 = 82
R5 — Light bluish green
R5 = 79
R6 — Light blue
R6 = 77
R7 — Light violet
R7 = 87
R8 — Light reddish purple
R8 = 71
R9 — Strong red
R9 = 25
R10 — Strong yellow
R10 = 58
R11 — Strong green
R11 = 80
R12 — Strong blue
R12 = 49
R13 — Skin tone (light pink)
R13 = 82
R14 — Leaf green
R14 = 89
The swatches represent calculated chromaticity within the limitations of an sRGB display. A monitor cannot reproduce the full spectral properties of a light source — different SPDs can map to the same display color while rendering real objects differently.
Same Ra — different spectrum, different rendering
Source A and Source B below are both ~2900 K white sources that compute the same General CRI (Ra), yet their spectra — and their R9 — differ substantially. Ra alone does not identify a spectrum, and it does not predict R9.
Source A — Ra ≈ 90, lower R9
Orange-red phosphor: strong R1–R8, weak deep red
TCS09 "Strong red" — reference vs. this source
Source B — Ra ≈ 90, high R9
Deep-red phosphor: same Ra, different spectrum
TCS09 "Strong red" — reference vs. this source
The takeaway: same CRI does not mean same spectrum or same color rendering. Two sources with nearly identical Ra can differ in spectral power distribution, R9, hue shifts, and saturation behavior. Evaluating a source for color-critical work means looking at the spectrum and the individual indices, not a single averaged number.
What General CRI (Ra) does — and does not — tell you
Ra tells you
- The average color fidelity of the first eight CIE test color samples relative to a reference illuminant of similar CCT.
- A quick, widely reported screening value for comparing broadly similar sources.
- That a source with a very low Ra will render many colors with visible errors.
Ra does not tell you
- R9 or any other individual index — R9 is a separate special color rendering index and cannot be reliably inferred from Ra.
- The shape of the spectrum: very different SPDs can produce the same Ra.
- Saturation behavior, hue shifts, or how one specific material will appear.
- Whether a source is suitable for a specific application on its own.
Choosing CRI in practice
Higher Ra values are commonly specified where color fidelity is important, but professional lighting selection should also consider the spectral power distribution, R9, TM-30 metrics, chromaticity (CCT and Duv), application requirements, and visual preference. No single averaged index determines whether a source is appropriate for museums, retail, healthcare, residential, or any other application.
Professional color-rendering evaluation often considers CRI together with additional metrics such as IES TM-30 (Rf, Rg and the color vector graphic). TM-30 values must be calculated independently from the SPD — they are not shown here because this tool does not currently implement the TM-30 calculation.
Need a specific CRI or R9 spec for your project?
Tell us about your application — our engineering team can recommend a suitable CRI/R9 combination and share measured spectral data for specific products.