Color perception

Color perception

Wrong representation

wavelength

sensibility

Complementary colors

Wrong representation

HLSHLS : Hue, Lightness, Saturation : Hue, Lightness, Saturation

Primary wavelength

Perceived luminance

Purity orvividness

Color Models :Color Models : Color SpacesColor Spaces

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Color Components (cont.)

• Lightness • Saturation

Compute Complementary colors

• Color = (R, G, B)• Complementary(color) = ( 1 - R, 1- G, 1- B)• Adjust brightness an saturation• http://www.colorjack.com/sphere/

wavelength

sensibility

energy

Color Models :Color Models : Color PerceptionColor Perception

bBgGrRC C alone cannot be constructed as the superpositions of POSITIVE amounts of the THREE primary colors (r, g, b)

Color Models :Color Models : Color PerceptionColor Perception

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Color Sensitivity & Image Detection

• Most sensitive to the center of the spectrum– blues & reds must be brighter than greens & yellows

• Brightness determined mainly by R+G – expressed on a scale of luminance

• light energy corrected for wavelength sensitivity

• Shapes detected by finding edges– combine brightness & color differences for sharpness

• Implications?– hard to deal w/ blue edges & blue shapes

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Color Sensitivity (cont.)

• As we age– lens yellows & absorbs shorter wavelengths

• sensitivity to blue is even more reduced

– fluid between lens and retina absorbs more light• perceive a lower level of brightness

• Implications?– don’t rely on blue/black differences for text or

small objects!

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Focus

• Different wavelengths of light focused at different distances behind eye’s lens– need for constant refocusing (causes fatigue)– careful about color combinations

• Red objects appear closer than blue objects• Pure (saturated) colors require more focusing

then less pure (desaturated)

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Color Guidelines

• Use harmonies of Complementary colors

• Avoid simultaneous display of highly saturated, spectrally extreme colors– e.g., no cyans/blues at the same time as reds,

why?• refocusing!

– desaturated combinations are better pastels

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Summary

• Color can be very helpful, but• Pay attention to

– how colors combine– Borders and contrast

• Be sensitive to people with limitations– people with color deficiency– color blindness, near/far sighted, and focusing

speed