Early artists used ochre to add red Colors are not always the same from culture to culture Blackbody Radiators A theoretical model of how objects emit radiation based on temperature Examples Incandescent light 2854K ID: 783121
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Slide1
Importance of Color
Painters first used charcoalEarly artists used ochre to add redColors are not always the same from culture to culture
Slide2Blackbody Radiators
A theoretical model of how objects emit radiation based on temperatureExamplesIncandescent light 2854K
Direct
sunlight 4874K
Slide3Emotional Response to Color
Temperature is associated with colorsBlue is coldRed is warmDepends on overall scene illumination
Slide4Thomas Young
English Physician1773-1829Every color can be matched by adding three primaries
Slide5Hermann Helmholtz
German Scientist1821-1894Verified Young's theory by identifying three types of receptors in the eye in 1852-3Invented
opthalmoscope
Slide6Retinal Structure
Slide7Color Vision
Each cone type is sensitive to a different rangeResearch indicates we can see about 10 million colorsHow can one color be distinguished from another?
How are colors specified?
Slide8Color Vision
Depends on relative stimulation of photoreceptorsDepends on wavelengthMonomersSame colors
Different spectra
Color depends on surrounding colors
Slide9Color Deficiency
About 10% have some deficiency9% men1% women
Most missing red or green cones
Red and green
percieved as brown
Monochromats
have only rods
Dichromats
have 2 of the three conesLow light vision is not affectedCare needs to be taken when creating visual materials for othersWeb pagesBrochuresDesign in black and white, then add color
Slide10Color Blindness
ProtanopiaNo red conesRed, orange, and yellow are shifted toward green
Violet is shifted towards blue
severe cases
traffic lights are black
Purple flowers are blue
Problems in extreme lighting conditions
Slide11Color Blindness
DeutanopiaNo green conesGreen, yellow, and orange are shifted toward red
Poor
discrimination
of blues
Slide12Color Blindness
TritanopiaNo blue cones
Slide13Ishihara Tests
Slide14Quantifying Color
CIE Commision Internationale
d'Eclairage
began work in 1931
First chart in 1947
Slide15CIE Chart
Revised in 1976Spectral colors (pure tones) are around perimeter curvePurple line is notNeutral color point
Complementary colors
Primary hue
Slide16CIE Chart
Slide17Color Gamut
Only a small subset of possible perceivable colors can be reproducedFall into convex hull of primaries
Two primaries results in a line
Three primaries results in a triangle
Slide18RGB Color Model
Additive colorsThree primariesRedGreen
Blue
Roughly match the sensitivities of cones
Used in digital images
Used in emissive color displays
Slide19Slide20CYMK Color Model
Subtractive color modelStarts with whiteReduces reflected lightThree primaries
Cyan
Yellow
Magenta
Black (key) is used to reduce brightness without changing the hue
Slide21CYMK Color Model
Slide22Complementary colors
OppositesEnhance one another because of optimal color contrast
Slide23Slide24Slide25Slide26