The image is captured with a camera sensor as brightness values of particular colours, each shown as grayscale. Consequently all the colour in the image is made from grayscale channels. So what you capture and what you edit is grayscale (which again is nothing more than a bunch of numbers). Colour is provided by the output (eg. monitor, printer)!

To see channels of an image in Photoshop, open the channels panel (found next to the layers panel or accessed through the menu windows/channels .

This particular image has three channels of the RGB colour space: red, green and blue. Each of these channels is grayscale (you can see that by clicking on them, as well as in the preview icon). You can also think of the channels as colour layers, so in RGB colour space there would be red, green and blue colour layer.

The “RGB” at the top is a composite channel of all those three channels (that’s why all three of them are also selected). If any of those channels is not selected, the “RGB” at the top won’t be shown selected.

Also notice that each channel has its own keyword, starting with ctrl + number of the channel. It is very helpful to memorize these keywords for faster workflow in Photoshop.

Channels are important to understand (or at least it is good to know they are there) when editing an image, because you can edit each channel seperately (= you can edit each colour seperately) or two or more channels together. You can do that by selecting particular channel (or more by holding down the shift key) in the channels panel or in some of the adjustment layers (like Levels, Curves) directly.

Individual colour channels hold brightness values of a particular colour in grayscale values, where the dark areas (black) signify there is not much or no such colour in that particular part of the image, bright areas (white) mean the colour in that particular part of the image is intense and the gray tones apply to the values in between.

Different colour spaces have different number (and type) of channels.

Colour channels can have different bit-depths, for example 8-bits channel, 12-bits channel, 16-bits channel, 24-bits channel, 32-bits channel..

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