Understanding color

In Adobe Photoshop Elements, you use two color models to manipulate color. One model is based on the way the human eye sees color—hue, saturation, and brightness (HSB), while the other model is based on the way computer monitors display color (in amounts of red, green, and blue or RGB). The color wheel is another tool that helps you understand the relationships between colors. Photoshop Elements provides four image modes that determine the number of colors displayed in an image: RGB, bitmap, grayscale, and indexed color.

The human eye perceives color in terms of three characteristics—hue, saturation, and brightness (HSB)—whereas computer monitors display colors by generating varying amounts of red, green, and blue (RGB) light. In Photoshop Elements, you use the HSB and RGB color models to select and manipulate color. The color wheel can help you understand the relationships between colors.

HSB model

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

The 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.

The strength or purity of the color. Saturation, which is sometimes called chroma, 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.

The relative lightness or darkness of the color, usually measured as a percentage from 0 (black) to 100 (white).

Although you can use the HSB model in Photoshop Elements to define a color in the Color Picker dialog box, you cannot use the HSB mode to create or edit images.

RGB model

A large percentage of the visible spectrum can be represented by mixing red, green, and blue (RGB) light in various proportions and intensities. These three colors are called the additive primaries. Added together, red, green, and blue light make white light. Where two colors overlap, they create cyan, magenta, or yellow.

The additive primary colors are used for lighting, video, and monitors. Your monitor, for example, creates color by emitting light through red, green, and blue phosphors.

Color wheel

The color wheel is a convenient way to understand and remember the relationship between colors. Red, green, and blue are the additive primaries. Cyan, magenta, and yellow are the subtractive primaries. Directly across from each additive primary is its complement: red-cyan, green-magenta, and blue-yellow.

Each subtractive primary is made up of two additive primaries, but not its complement. So, if you increase the amount of a primary color in your image, you reduce the amount of its complement. For example, yellow is composed of green and red light, but there is no blue light in yellow. When adjusting yellow in Photoshop Elements, you change the color values in the blue color channel. By adding blue to your image, you subtract yellow from it.