Knowing RGB Basics in Photoshop

When you view an RGB image, you are looking at an image comprised of three colors — red, green, and blue. These colors are:

-->The primary colors of light
-->The colors that correspond to the three types of cones inside your eyes
-->The colors that comprise white light from the sun
-->The colors your monitor uses when displaying images

Mixing these three primary colors can yield up to 16.7 million colors. In Photoshop, each of these colors resides in a color channel in the image. Photoshop looks at a color image in terms of its channels — individual bands of 8-bit grayscale images. When you view the channels individually in Photoshop, you can visually see that each channel appears as a grayscale image made up of light-, medium-, and dark-colored pixels (assuming that you have deselected the Color Channels in the Color check box). RGB images have three bands, and CMYK images have four bands. Each one of these bands, or grayscale images, is a channel, or more specifically a color channel. When you view the channels together, the pixels from each channel mix to form colors, which give you a composite, or full-color image.

Photoshop assigns each pixel a brightness value ranging from 0 (black) to 255 (white). These grayscale pixels from each channel mix together to form colors, which in turn provide you with a composite color image. Here are some color channel examples to help you see how the RGB system works to create so many different color variations:

-->A light-colored pixel from the green channel, a dark-colored pixel from the red channel, and a dark-colored pixel from the blue channel combine to give you a green pixel.
-->A value of 255 from all three channels produces white.
Because RGB colors combined at 255 create white, they are known as additive colors.
When you view this white on your computer monitor, for example, it transmits all visible wavelengths back to your eyes.
-->A value of 0 from all three channels produces black.
-->If all three values are equal, a neutral gray is produced.
-->A medium-dark pixel from the red channel, a black pixel from the green channel, and a light-colored pixel from the blue channel combine to produce purple.
-->Mixing colors in RGB produces lighter colors. Try playing with the RGB color sliders in your Color palette and mix your own colors to see this concept in action. Remember that the right side of the slider (the higher numbers) represents light, and the left side of the slider (the lower numbers) represents dark.