Operation Manual

USING PHOTOSHOP

Color fundamentals

Last updated 12/5/2011

Adobe RGB

, sRGB, ProPhoto RGB, and so on.

Each device, like your monitor or printer, has its own color space and can only reproduce colors in its gamut. When

an image moves from one device to another, image colors may change because each device interprets the RGB or

CMYK values according to its own color space. You can use color management when moving images to ensure that

most colors are the same or similar enough so they appear consistent. See Why colors sometimes don’t

match.

In Photoshop, a document’s color mode determines which color model is used to display and print the image you’re

working on. Photoshop bases its color modes on the color models that are useful for images used in publishing. You

can choose from RGB (Red, Green, Blue), CMYK (Cyan, Magenta, Yellow, Black), Lab Color (based on CIE L*

a* b*),

and Grayscale. Photoshop also includes modes for specialized color output such as Indexed Color and Duotone. Color

modes determine the number of colors, the number of channels, and the file size of an image. Choosing a color mode

also determines which tools and file formats are available. See

“Color modes” on page 89.

When you work with the colors in an image, you are adjusting numerical values in the file. It’s easy to think of a

number as a color, but these numerical values are not absolute colors in themselves—they only have a color meaning

within the color space of the device that is producing the color.

Adjusting color hue, saturation, and brightness

Based on the human perception of color, the HSB model describes three fundamental characteristics of color:

Hue Color reflected from or transmitted through an object. It is measured as a location on the standard color wheel,

expressed as a degree between 0° and 360°. In common use, hue is identified by the name of the color, such as red,

orange, or green.

Saturation Strength or purity of the color (sometimes called chroma). Saturation represents the amount of gray in

proportion to the hue, measured as a percentage from 0% (gray) to 100% (fully saturated). On the standard color

wheel, saturation increases from the center to the edge.

Brightness Relative lightness or darkness of the color, usually measured as a percentage from 0% (black) to 100%

(white).

HSB color model

H. Hue S. Saturation B. Brightness

Color modes