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Color Models & Color Space. 5 ways of specifying colors. Color Models. RGB - mixing primary light colors CMYK - mixing primary pigment colors Indexed color - matching colors on screen to a specific color table Lab color - international standard, device independent
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Color Models & Color Space 5 ways of specifying colors Multi-media Graphics JOUR 205
Color Models • RGB - mixing primary light colors • CMYK - mixing primary pigment colors • Indexed color - matching colors on screen to a specific color table • Lab color - international standard, device independent • HSB - hue, saturation & brightness Multi-media Graphics JOUR 205
Additive color model (RGB) • Red, blue & green are primary colors • Applies when mixing colors of light (on tv & computer screens, theatrical lighting) • Mixed primaries make white light Multi-media Graphics JOUR 205
An RGB color image Red channel only Red + Green Red + blue + green Green + blue Multi-media Graphics JOUR 205
Subtractive color model (CMYK) • Cyan, magenta & yellow are primary colors • Applies when pigments are mixed on a surface (printing, painting, etc.) • Mixed primaries make “black” Multi-media Graphics JOUR 205
Elements of a CMYK image Multi-media Graphics JOUR 205
C + M printers Multi-media Graphics JOUR 205
C + M + Y printers Multi-media Graphics JOUR 205
C + M + Y + K printers Multi-media Graphics JOUR 205
The Lab color model • Three axes (L, a & b) define a “color space.” • All colors can be precisely defined by their position in this space. • Lab model is a world-wide standard for all monitors & printers. Multi-media Graphics JOUR 205
Elements of an Lab image Luminance (L) Color axis a (green/magenta) Color axis b (yellow/blue) Multi-media Graphics JOUR 205
HSB color model HSB model is based on human perception of color, represented by the color wheel. Multi-media Graphics JOUR 205
HSB color model • Hue is the color reflected from or transmitted through an object. Hue is identified by the name of the color. • Saturation represents color purity-- the amount of gray in proportion to the hue. • Brightness is the relative lightness or darkness of the color. Multi-media Graphics JOUR 205
Photoshop’s HSB controls Normal image Image with hue, saturation and brightness altered. Multi-media Graphics JOUR 205
Color gamuts Multi-media Graphics JOUR 205
Out-of-gamut colors Colors specified in RBG Colors printed in CMYK Colored inks on paper cannot reproduce the bright, intense colors that are possible when mixing with light on a monitor. If your art is to be printed on paper, specify colors in CMYK mode to avoid “color shock” when your job comes back from the print shop. Multi-media Graphics JOUR 205
Index color: web-safe palette Original RGB format Image indexed to web palette 24-bit RGB images may contain 16.7 million colors. Index color images can have no more than 255 colors. The web-safe palette has only 216 colors. Those colors are common to both Macintosh and Windows operating systems. Multi-media Graphics JOUR 205