Color perception

Wrong representation

wavelength sensibility

Complementary colors

Wrong representation

HLS : Hue, Lightness, Saturation Primary wavelength Perceived luminance Purity or vividness Color Models : Color Spaces

2/24/9912 Color Components (cont.) Lightness Saturation

Compute Complementary colors Color = (R, G, B) Complementary(color) = ( 1 - R, 1- G, 1- B) Adjust brightness an saturation

wavelength sensibility energy

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

Color Models : Color Perception

2/24/9917 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

2/24/9920 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!

2/24/9921 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)

2/24/9922 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

2/24/9923 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