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Photoshop CS3 Color Picker

Choosing a RGB, CMYK & Hexadecimal Color Space

The Photoshop "Color Picker" palette window allows you to select a color by sampling a "Foreground Color" from an existing image, using the "Eyedropper Tool" (I) located in the Photoshop Tool Pallet.

Once you have sampled the desired color you can find that color's RGB, CMYK, or Web Pallet "Hexadecimal" (#) color formulas. You can also manually enter CMYK percentages and Hexadecimal or RGB values and your selection will be displayed in the "Select Foreground Color" viewing box located in the Photoshop Tool Pallet.

Technical Note: You can set the sensitivity of the Eyedropper Tool by setting the "Sample Size" to "Point Sample," "3 by 3 Average," or 5 by 5 Average in the tool bar. If you are sampling from a photo with a lot of noise, use the "3 by 3 Average" setting to simulate (average) the perceived color.

RGB Additive & CMYK Subtractive Color

The diagram above illustrates the difference between Additive Color (RGB or "Red, Green, Blue") Fig. 1, and Subtractive Color (CMYK or Cyan, Magenta, Yellow, Black) Fig. 2. When you combine Red, Green, and Blue in the Additive Color process, the combination produces white. In the Additive Color process, white is the combination of all colors. In the Subtractive Color (CMYK) process, when you combine Yellow, Cyan, and Magenta (CMY), the combination produces black. In the Subtractive Color process, black is the combination of all colors.

RGB equivalents are expressed in numeric values from 0 to 255. An RGB numeric value of "0, 0, 0" creates a solid black, while a numeric value of "255, 255, 255" creates pure white.

Hexadecimal Web Color Equivalent

A hexadecimal color value, or "hex triplet" is a six-digit, three-byte numeric code number used in HTML web page code and CSS style sheet code. The bytes represent red, green, or blue components in a given color. In the hexadecimal system (hexadecimal notation), numbers in the range 00 to FF are used, as opposed to 0 to 255 in RGB decimal notation.

R/16 = x + y/16
G/16 = x' + y'/16
B/16 = x" + y"/16

To calculate a hexadecimal equivalent for RGB, you would divide each three digit number by sixteen (ignoring any remainder) to obtain the first hexadecimal digit. Letters ranging from A to F will represent numbers 10 to 15. The second digit in each two digit number is obtained by multiplying the remainder by 16.

Photoshop Hexadecimal Web Color Equivalents

Lab Color Space

Based on the Munsell color system, the Lab color space, which is an abbreviation for CIE 1976 (L*, a*, b*), or CIELAB is designed to approximate human vision, with the dimension "L" representing luminance and "a" or "b" representing the Red/Green" and "Yellow/Blue" color-opponent dimensions. Some of the colors contained within the Lab color space fall outside the gamut of human vision, and requires more data per pixel than a CMYK or RGB file.

HSB Color Space

The HSB color space, also known as the HSL (hue, saturation, lightness) or HSV (hue, saturation, value) color space, identifies colors as points within a cylinder. The cylinder's central axis ranges from black at the bottom to white at the top with neutral shades of grey in between. Moving from the central axis towards the outer edge of the cylinder represents increasing saturation, and hue changes occur along the outer diameter.

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