Short answer
A CIE illuminant is a table of relative spectral power — a defined 'light' for calculating colour — not a physical lamp. A represents tungsten light (about 2856 K); D65 and D50 represent average daylight at about 6500 K and 5000 K; the F-series represent fluorescent lamps; and CIE 15:2018 added LED illuminants. D65 is the default for most industries and for screens, D50 for the graphic arts, because each industry standardised on the light its products are judged under.
To calculate an object's colour you need the light's spectrum. The CIE therefore publishes illuminants: relative spectral power distributions at 5 nm or 1 nm steps that everyone can use in the same calculation. Illuminant A is defined by the formula for a blackbody at about 2856 K, representing tungsten filament light. The D series is derived from measured daylight and defined for any correlated colour temperature; D65 and D50 are the two most used. Real 'D65' lamps in viewing booths only approximate the table, especially in the ultraviolet, which matters for fluorescent samples.
D65 was recommended by the CIE as the representative daylight for colorimetry and became the default for paint, plastics, textiles, and — through sRGB and HD television — screens. The graphic arts settled on D50, a warmer daylight, for print viewing and measurement: ISO 3664 viewing booths and ISO 13655 measurement use D50, and all print characterisation data are D50. The two are not interchangeable in a calculation. Converting CIELAB between them needs a chromatic adaptation transform, which is an approximation, so it is better to recompute from spectral data under the illuminant required.
The F-series represent fluorescent lamps of the mid-twentieth century onwards: F2 a cool-white halophosphate lamp (about 4230 K), F7 a broadband daylight simulator (about 6500 K), and F11 a narrow three-band lamp (about 4000 K, the type retailers often call TL84). Their spiky spectra make them good tests of metamerism. CIE 15:2018 added LED illuminants: five phosphor-converted blue LEDs (LED-B1 to B5, from about 2733 K to 6598 K), a hybrid blue-and-red type (LED-BH1), an RGB-mixed type (LED-RGB1) and two violet-pumped types (LED-V1, V2). They let a specification test a match under the light people now actually live with.
A colour specification normally names a primary illuminant for the tolerance and one or two secondary illuminants for a metamerism check. A common pattern in consumer goods is D65 as primary, with a tungsten-type (A) and a store-lighting type (F11 or an LED illuminant) as secondaries. For print, D50 is primary. The computed table on this page shows how far apart the illuminants' own chromaticities are. A sample pair that matches under D65 and drifts apart under A or LED is metameric, and that is a reason to reformulate, not to widen the tolerance.
| Illuminant | x | y | CCT (computed) |
|---|---|---|---|
| Incandescent tungsten, CIE A | 0.4475 | 0.4074 | 2860 K |
| Daylight, CIE D50 (graphic arts viewing) | 0.3457 | 0.3586 | 5000 K |
| Daylight, CIE D65 | 0.3128 | 0.3291 | 6500 K |
| Cool-white fluorescent, CIE FL2 | 0.3713 | 0.3731 | 4240 K |
| Narrow-band tri-phosphor fluorescent, CIE FL11 | 0.3796 | 0.3761 | 4030 K |
| Phosphor-converted white LED, CIE LED-B3 | 0.3758 | 0.3730 | 4110 K |
| Red-green-blue mixed LED, CIE LED-RGB1 | 0.4557 | 0.4210 | 2840 K |
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactStrong evidence
CIE illuminant A has a correlated colour temperature of about 2856 K, D65 about 6504 K and D50 about 5003 K.
Source: Light sources and illuminants; CIE 015:2018 Colorimetry, 4th edition; Standard illuminant (Wikipedia)
StandardStrong evidence
CIE 15:2018 (Colorimetry, 4th edition) introduced illuminants for LED lighting: LED-B1 to LED-B5 (phosphor-converted blue, about 2733 K to 6598 K), LED-BH1 (hybrid), LED-RGB1 (RGB mixed) and LED-V1 and LED-V2 (phosphor-converted violet).
Source: CIE 015:2018 Colorimetry, 4th edition; Light sources and illuminants
FactStrong evidence
Among the F-series fluorescent illuminants, F2 represents a cool-white lamp at about 4230 K, F7 a broadband lamp at about 6500 K and F11 a narrow tri-band lamp at about 4000 K.
Source: Light sources and illuminants
StandardStrong evidence
Graphic-arts measurement condition M1 in ISO 13655 requires specimen illumination matching D50, consistent with the D50 viewing conditions of ISO 3664.
Colourwise analysisStrong evidence
Computed from the CIE spectral tables at 10 nm band means with the 1931 2° observer, all seven illuminants in the table — including the line-spectrum fluorescents FL2 and FL11 — reproduce their nominal correlated colour temperatures to within about 30 kelvin.
Based on: Colourwise integrated each CIE illuminant's SPD against the CIE 1931 colour-matching functions, both averaged over 10 nm bands from the CIE's 1 nm tables, and estimated CCT from the resulting chromaticity with McCamy's approximation.
Caveat: How the spectrum is reduced to 10 nm matters. Taking every tenth 1 nm value instead of the band mean steps over fluorescent lines: FL11 then computes near 1,900 K. McCamy's formula is itself an approximation that is only meaningful near the Planckian locus.
Source: CIE datasets (colour-matching functions, illuminants)
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.