Channels

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The Channels Pallet looks a lot like the Layers Pallet. It’s function isn’t as obvious as the Layers Pallet and you could be forgiven for thinking that its existence is just an attempt to make your life more complex. In fact, in day to day PS use you can get by without it. However, such is the abiding importance to channels in image editing that the very first book ever written on PS use was called Channel Operations. An understanding of channels can make your life as a digital painter and PS gure a lot easier. .

Tip: when working with Channels makes sure the Channels Pallet is visible next to (and not on top of) the layers Pallet.

Channels as the medium of color

When a computer draws a yellow dot on your screen it is not thinking to itself ‘yellow dot’ it is thinking ‘Red dot at maximum value, Green dot at maximum value and Blue dot at minimum value, all projected on top of each other’’ or R = 255, G = 255, B = 0. These are the three projected light primaries (different from the pigment primaries that a traditional painter would use). In a PS document these different group of information are stored in the Channels. The proof:

  • Make a new document in RGB and fill it with black.
  • Go to the Channels Pallet where you will see the RGB composite and the R G and B channels.
  • Click once in the R channel (this will isolate it) and draw a big, thick white line (you will notice that once you are in an isolated channel you can only paint in grey scale, not color).
  • Repeat in the other channels, making sure that each line is at a different orientation to the other..
  • Look at them in the composite channel. They should look something like this:

Channels pallet 02.png

Channels as the medium of selections

When a selection is saved through the Select menu it is placed as a new channel in the Channels Pallet. I find that it is not often necessary to save selections, but of you do either of the two alternate methods are far quicker and more straightforward:

  • After the selection is made press the Save selection as channel button at the bottom of the Channels Pallet.
  • Press the Add layer mask button, found at the bottom of the layers pallet.

The fugitive channel

The Channels Pallet has some peculiarities of behavior. Channels seem to appear and disappear at will.

Try this: make two layers (called layer 1 and layer 2) and add a Layer Mask to layer 2. You will see that when you are 'in' layer 2 its mask is visible as a new channel in the Channels Pallet, to disappear when you navigate away from it.

Try also this: after having made a selection press the activate Quick Mask Mode (press the Q key). You will see again a new channel appear in the Channels Pallet, to disappear when you leave Quick Mask Mode (press Q again).

And this: make from a selection a new channel in the Channel Pallet (Alpha 1). Press the eye icon next to it so that the RGB and Alpha 1 channels are all visible. The selection is visible as a red overlay that is identical to the one you get when you activate Quick Mask Mode.

Apart from the whimsical nature of the interface design that has governed the Channels Pallet, I am trying to make the point that: Quick Masks, selections, Layer Masks etc are all the same thing. Another way of saying the same thing is this:

Channels pallet 01.png