Kruithof curve

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The Kruithof curve, with two example light sources; D65 (Northern daylight) and a 3700 K halogen lamp, inside the pleasing region.
The Kruithof curve, with two example light sources; D65 (Northern daylight) and a 3700 K halogen lamp, inside the pleasing region.[1]

Named after the Dutch engineer Arie Andries Kruithof,[2] the Kruithof curve relates the illuminance and colour temperature of visually-pleasing light sources.

The colour sensation of a given light mixture may vary with absolute luminosity, because both rods and cones are active at once in the eye, with each having different colour curves, and rods taking over gradually from cones as the brightness of the scene is reduced. This means, for example, that light with a colour temperature of 6000 K may appear white under high luminance, but appear bluish under low luminance. Under the same low luminance conditions, the colour temperature may need to be adjusted to, say, 4700 K, to appear white. This effect leads to a change in colour rendition with absolute illumination levels that can be summarised in the empirical Kruithof curve.[3]

As the brightness of the scene decreases, the brightness of red colours decreases more rapidly than those of blue colours, this being the so-called Purkinje effect.[4]

[edit] References

  1. ^ Weintraub, Steven (September 2000). "The Color of White: Is there a "preferred" color temperature for the exhibition of works of art?". Western Association for Art Conservation Newsletter 21 (3). 
  2. ^ Kruithof, Arie Andries (December 12 1934). Aanslag van het waterstofmolecuulspectrum door electronen. (PhD dissertation at Utrecht University under Leonard Ornstein) (Dutch)
  3. ^ Kruithof, Arie Andries (1941). "Tubular Luminescence Lamps for General Illumination". Philips Technical Review 6 (3): 65-96. ISSN 0031-7926. 
  4. ^ Frisby, John P. (1980). Seeing: Illusion, Brain and Mind. Oxford: Oxford University Press. ISBN 978-0192176721. 

[edit] Further reading

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