Color

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React only to some wavelengths, with different sensitivity (light fraction absorbed)

Brain fuses responses from local neighborhood of several cones for perceived color

Sensitivities vary per person, and with age

Color blindness: deficiency in at least one type of cone

Three kinds of cones

Types of cones

Slide 51

Possible evolutionary pressure for developing receptors for different wavelengths in primates

Osorio & Vorobyev, 1996

Types of cones

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Trichromacy

Experimental facts:

Three primaries will work for most people if we allow subtractive matching; “trichromatic” nature of the human visual system

Most people make the same matches for a given set of primaries (i.e., select the same mixtures)

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Environmental effects & adaptation

Chromatic adaptation:

We adapt to a particular illuminant

Assimilation, contrast effects, chromatic induction:

Nearby colors affect what is perceived; receptor excitations interact across image and time

Afterimages

Color matching != color appearance

Physics of light != perception of light

Slide 54

Chromatic adaptation

If the visual system is exposed to a certain illuminant for a while, color system starts to adapt / skew.

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Chromatic adaptation

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Brightness perception

Edward Adelson

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Edward Adelson

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Edward Adelson

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Look at blue squares

Look at yellow squares

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Content © 2008 R.Beau Lotto