Generator
Colourfulness rises with light level; apparent contrast does not
Predicted colourfulness M for one stimulus across four decades of adapting luminance, and the exponent of the lightness curve over the same range. M rises by a factor of 2.24 — the Hunt effect, which the model does predict. The lightness exponent changes by -2.2%, and in the wrong direction — the Stevens effect, which it does not.
Drawn at its defaults, in appearance modelling.
It reads 2 options and
no others: levels, obs.
Called by 2 essays
the blast radius of changing it
What the brain does
Brighter looks more colourful
Colourfulness rises with light level and the model predicts it. Apparent contrast is supposed to rise too, and the model does not — which turns out to be right, because the thing that actually carries contrast is the surround.
What the brain doesBrightness is not luminance
Photometry is additive because the CIE defined it that way. Brightness is not, and a saturated colour looks as bright as a neutral of one and a half times its luminance — an effect this site's appearance model moves by two per cent, in a direction that depends on the hue.