A tabulated spectral power distribution representing average daylight including its ultraviolet portion. No lamp reproduces it exactly, so instruments adjust their UV content with fluorescent reference standards until brightened samples read as they would under true D65. It is the basis for D65 brightness and for the outdoor-daylight versions of CIE whiteness and CIELAB paper color.
Under D65 the new sheet reads 165 CIE, but in an office lit by LEDs it looks flat because there's no UV to wake the OBA.
Also heard as
- D65
- CIE illuminant D65
Related terms
Illuminant C
Standard CIE light distribution approximating average daylight, with relatively little ultraviolet.
D65 brightness
Diffuse blue reflectance at 457 nm measured with the instrument's UV content tuned to daylight illuminant D65.
CIE whiteness
Formula-based whiteness index computed from luminance factor Y and chromaticity, under D65 or C illumination.
UV calibration
Setting an instrument's ultraviolet content so fluorescent samples read as they would under the specified illuminant.