Wavelength and Light

Nan

omet

ers

Monochromators measure the power or energy at different wavelengths

Typical daylight SPDs vary

Superposition of Light SPDs

Rod Color Matching

Example Data: Rod Matches

Photopigment Absorptions

Rhodopsin Absorption Curve

Rhodopsin Predicts Matches

Cones and Color Matching (Roorda et al.)

Cone inner segments have a diameter of roughly 1-2 micron in foveola and much larger in the periphery. Here (foveolar edge) they are about 3-4 microns(330 microns ~ 1 deg)

Cone Color Matching Experiment

Color Matching Is An Important Illusion That Is Understood

Quantitatively

The Color Matching Experiment Is Linear

If

and matches

matches

then matches

More metamer examples; this is a big effect.

RGB

CIE RGB functions Response

InputSPD

Color Matching Experiment Equation

Standard CMFs (10 deg)

Single Unit Cone Photocurrent Measurements (Schnapf, Baylor et

al).

Current Recordings From a Cone

There are Three Types of Cone Wavelength Responsivity

Stimuli Causing Equal Cone Signals Match Perceptually

L

M

S L M S

Abs

orpt

ion

rate

Cone type

Behavioral CMFs are accurately predicted by cone responsivities

Color Matching and Context

Illumination And Color

Appearance Are Closely

Coupled Through

Color Constancy

Blue Blue SkySky

Direct Direct SunSun