Adobe Photoshop CS4 - Manual (Page 129)

122 USING PHOTOSHOP CS4
Color fundamentals
Last updated 1/10/2010
Choose a color using the Lab model
When choosing a color based on the Lab color model, the L value specifies the luminance of a color. The A value
specifies how red or green a color is. The B value specifies how blue or yellow a color is.
1 In the Adobe Color Picker, enter values for L (from 0 to 100), and for A and B (from -128 to +127).
2 (Optional) Use the color slider or color field to adjust the color.
Choose a color using the CMYK model
You can choose a color by specifying each component value as a percentage of cyan, magenta, yellow, and black.
❖ In the Adobe Color Picker, enter percentage values for C, M, Y, and K, or use the color slider and color field to
choose a color.
Choose a color by specifying a hexadecimal value
You can choose a color by specifying a hexadecimal value that defines the R, G, and B components in a color. The three
pairs of numbers are expressed in values from 00 (minimum luminance) to ff (maximum luminance). For example,
000000 is black, ffffff is white, and ff0000 is red.
❖ In the Adobe Color Picker, enter a hexadecimal value in the # text box.
Choose web-safe colors
The web-safe colors are the 216 colors used by browsers regardless of the platform. The browser changes all colors in
the image to these colors when displaying the image on an 8-bit screen. The 216 colors are a subset of the Mac
OS 8-bit
color palettes. By working only with these colors, you can be sure that art you prepare for the web will not dither on a
system set to display 256 colors.
Select web-safe colors in the Adobe Color Picker
❖ Select the Only Web Colors option in the lower left corner of the Color Picker. Any color you pick with this option
selected is web-safe.
Change a non-web color to a web-safe color
If you select a non-web color, an alert cube appears next to the color rectangle in the Adobe Color Picker.
❖ Click the alert cube to select the closest web color. (If no alert cube appears, the color you chose is web-safe.)
Select a web-safe color using the Color panel
1 Click the Color panel tab, or choose Window > Color to view the Color panel.
2 Choose an option for selecting a web-safe color:
• Choose Make Ramp Web Safe from the Color panel menu. Any color you pick with this option selected is web-safe.
• Choose Web Color Sliders from the Color panel menu. By default, web color sliders snap to web-safe colors
(indicated by tick marks) when you drag them. To override web-safe color selection, Alt-drag (Windows) or
Option-drag (Mac
OS) the sliders.
If you choose a non-web color, an alert cube appears above the color ramp on the left side of the Color panel. Click
the alert cube to select the closest web color.