Understanding Channels and Bit Depth

Each color mode as a preset number of channels that, in Photoshop, cannot be changed. For example, the RBG color mode has three channels: red, green, and blue.

The bit depth determines how many colors are available. An image using the RGB color mode and a bit depth of 16 per channel is capable of producing 16.7 million different colors.

When creating an image from scratch, it's best to select the color mode and bit depth at the beginning. When you're working with an acquired image (from the Internet, a digital camera, or a scanner), use the image in its current color mode and bit depth for best results. When you're finished with the image, change the color mode and bit depth if required for the document's final output media.