Short answer
A white point is the colour a system treats as neutral white; every other colour in the space is defined relative to it. Screens and video standardise on CIE illuminant D65, a daylight of about 6500 K, while graphic-arts viewing and the ICC profile connection space use D50, about 5000 K. The difference is a convention about the light a result is judged under, and colour management bridges it with a chromatic adaptation transform rather than by treating one white as correct.
The CIE D-series illuminants are tabulated spectral power distributions representing phases of daylight. D65 corresponds to a correlated colour temperature of roughly 6500 K, a bluish north-sky daylight; D50 to roughly 5000 K, warmer and closer to direct sun plus sky. In chromaticity terms D65 sits at about x 0.3127, y 0.3290 and D50 at about x 0.3457, y 0.3585. Both are mathematical references, not lamps: no ordinary light source reproduces either spectrum exactly, which is why print viewing booths are specified by how close they come to D50 rather than by being D50.
Television adopted D65 for its studio white, and sRGB, Display P3, Adobe RGB and Rec. 2020 all inherited it, so a screen's 'white' is intended to match D65. Printing standardised its viewing booths and measurements on D50, whose spectrum better matches the mixed daylight under which printed matter has traditionally been judged. The ICC then used D50 as the reference white of the profile connection space, so every ICC conversion passes through a D50-relative description. CSS followed the colour-science convention for Lab: CSS lab() and lch() are D50-relative, whereas oklab() and oklch() are D65-relative because OKLab was defined that way.
Moving a colour description from a D65 world to a D50 world is not a matter of making everything warmer. Colour management applies a chromatic adaptation transform — CSS Color 4 specifies the linear Bradford transform — which predicts the colour that would look the same to an observer adapted to the other white. A D65 screen white becomes D50 paper white; a mid-grey stays grey. That is the correct behaviour for comparing a screen and a print each viewed under its own light, and it is why converting sRGB colours to CSS lab() changes the a* and b* numbers slightly compared with a D65-based Lab calculator. Neither is wrong; they are Lab relative to different whites.
Few screens ship exactly at D65. Factory settings often run bluer, because a cool white reads as brighter in a showroom. 'Warm', 'natural', night-shift and ambient-adaptive modes move the white deliberately. Calibration usually targets D65 for web and video work; some print-proofing setups target a white that matches the paper under the booth light, which can be closer to D50. Because the eye adapts, a screen's white always looks white after a minute or so — which is exactly why comparing a screen with a print side by side under daylight shows a colour cast the eye never notices on the screen alone.
| White | Approx. CCT | Chromaticity (x, y) | Used by |
|---|---|---|---|
| D65 | ≈ 6500 K | 0.3127, 0.3290 | sRGB, Display P3, Adobe RGB, Rec. 709/2020, OKLab, CSS xyz-d65 |
| D50 | ≈ 5000 K | 0.3457, 0.3585 | ICC profile connection space, CSS lab()/lch(), ProPhoto RGB, graphic-arts viewing |
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.
StandardStrong evidence
sRGB, Display P3, Adobe RGB (1998) and Rec. 2020 all specify a D65 white point.
Source: CSS Color Module Level 4; ITU-R Recommendations BT.709, BT.2020 and BT.2100
StandardStrong evidence
D50, a standardised daylight spectrum with a colour temperature of about 5000 K, is the white point used for the ICC profile connection space and for CSS lab() and lch().
Source: CSS Color Module Level 4; International Color Consortium: specifications and information
StandardStrong evidence
CSS Color 4 converts between D65 and D50 colour spaces with the linear Bradford chromatic adaptation transform.
Source: CSS Color Module Level 4
FactStrong evidence
The CIE publishes the D-series illuminants as tabulated spectral data; they are references for calculation rather than descriptions of any physical lamp.
Source: CIE 015:2018 Colorimetry, 4th edition; 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.