VSP3: Color Vision Part 3b

Spectral Hues

monochromatic hues along arc of perimeter

pure hues

spectral locus

the arc or location of points on the chromaticity diagram that represents color stimuli across the entire visible spectrum

Purple line

non spectral colors

Spectral locus includes

tristimulus values of pure spectral colors

colors along this arc have the maximum saturation

Which color cannot be produced with monochromatic light P

purple

Purple line

includes non spectral purples

line connecting 380 nm to 700 nm

Purples = combination Red and violet (blue)

white

falls in the middle

Chromaticity Diagrams Color Mixing: an additive mixture of two wavelength lies

on a line connecting the two wavelengths

This can be used to calculaten ______ of a color

dominant wavelengths

excitation purity

Dominant Wavelegnth

the wavelength that can be mixed with a reference white to give a match to that color

Excitation Purity

distance of the sample (M) along the line connecting white (W) to the perimeter of the arc

extent to which a color stimulus differs from white or its dominant wavelength, as determined by its location between them on a chromaticity diagram

Excitation Purity formula

a/ a+b

ratio of the distance from the reference white to the sample light (a)

divided by the distance from the white to the sominant wavelength

maximum = 1

(monofromatic lights)

reference white = 0

if it likes on the sepctral locus it has exitation putiy of

1

What is the excitation putiry at W point

0

Complementary Colors definitino

pairs of colors that match a specific white light when mixed in proper proportion

Complelent colors on the CIE diagramc

connect the reference wavelength though white to find any complementary color

Spectral compliments

380 to 490

570 to 700

No spectral complement

490 to 570

drawing a line though white would lead to purple line

Equal Energy white

(x,y)

(0.33, 0.33)

Can specify white in terms of color temperature of a

black body radiator (opaque object)

Black body radiator

opaque object that emits thermal electromagnetic radiation as its heated

high enough - begins to emit visible radiation

Ie iron horse shoe

Planckian locus

a collection of points on the chromaticity diagram representing black body radiations of various temperatires

arc of white in CIE daigram

Plankcian locus passes close to

equal energy white at 5,600k

Lower color temperatires

reddish white

Standard illuminant A

100 W incadenscent bulb

color temperatire od 2,855.6K

Medium color temperature

direct sunlight

standard illuminant B

Color temperatire of 4,874k

White

Higher color temperature =

bluish white = light from overcast north sky

Standard illuminant C - color vision testing

color temperature of 6,774K

SUMMARY SLIDE