Entering numeric color values

In addition to selecting colors using the slider and color field, you can enter specific color values in the option boxes in the lower-right region of the Color Picker dialog box. Novices and intermediates may find these options less satisfying to use than the slider and field. These options, however, enable artists and print professionals to specify exact color values, whether to make controlled adjustments to a color already in use or to match a color used in another document. The options fall into one of four camps:

♦ HSB: These options stand for hue, saturation, and brightness. Hue is measured on a 360-degree circle. Saturation and brightness are measured from 0 to 100 percent. These options permit access to more than 3 million color variations.

Figure 4-4: The results of selecting (top to bottom) the R (Red), G (Green), and B (Blue) radio buttons.

♦ RGB: You can change the amount of the primary colors red, green, and blue by specifying the brightness value of each color from 0 to 255. These options enable access to more than 16 million color variations.

♦ Lab: This acronym stands for luminosity, measured from 0 to 100 percent, and two arbitrary color axes, a and b, whose brightness values range from -120 to 120. These options enable access to more than 6 million color variations.

♦ CMYK: These options display the amount of cyan, magenta, yellow, and black ink required to print the current color. When you click the alert triangle, these are the only values that don't change, because they make up the closest CMYK equivalent.

At the bottom of the dialog box, the value next to the pound sign (#) shows you the hexadecimal value for the chosen color (see Figure 4-2). This value comes into play only if you're creating Web graphics — and maybe not even then.

In Web-land, every color is assigned a numeric value based on the hexadecimal numbering system. Each value includes a total of three pairs of numbers or letters, one pair each for the R, G, and B values. When you create a color tag in HTML code, you enter the hexadecimal value for the color you want to use. Fortunately, you can now create a Web page without having to write your own HTML code; today's page-creation programs do the work for you. But if you prefer to do your own coding — you lovable geek, you — make note of the hexadecimal value in the Color Picker dialog box.

Tip This option can also come in handy if you want to precisely match a color on an existing Web page. Just look at the HTML coding for the page, note the hexa decimal value in the appropriate color tag, and enter that value in the Color Picker dialog box.

In my opinion, the numerical range of these options is bewildering. For example, numerically speaking, the CMYK options enable you to create 100 million unique colors, whereas the RGB options enable the standard 16 million variations, and the Lab options enable a scant 6 million. Yet Lab is the largest color space, theoretically encompassing all colors from both CMYK and RGB. The printing standard CMYK provides by far the fewest colors, the opposite of what you might expect. What gives? Misleading numerical ranges. How do these weird color models work? Keep reading and you'll find out.

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Photoshop Secrets

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