Using channels

Colour modes and channels

For each colour mode, the following channels are available.

RGB: Red, Green, Blue channels
CMYK: Cyan, Magenta, Yellow, Black channels
Greyscale: Intensity channel
Lab: Lightness, AOpponent, BOpponent channels

Image and layer channels

The Channels panel always displays an image's channels when loaded. From an image channel you can:

Protect the channel from editing.
Hide the channel.
Create a spare channel (i.e., a saved selection) from any channel's information.
Store a new selection based on the channel information.
Add, subtract, or intersect a channel's selection to/from/with a previously made selection, respectively.

For any currently selected layer (pixel, mask, adjustment or live filter), the layer's channel(s) are displayed below the image channels. From each layer's channel you can:

Invert, clear, and fill the channel information.
Create a new greyscale layer.
Create a new mask layer.
Create a Spare Channel (i.e., a saved selection) from the channel information.

Alpha channels

The Channels panel also displays the alpha channel for the whole image or currently selected pixel, mask, adjustment, or live filter layer. These channels store transparency information, so it's a great place for more advanced masking control.

Pixel selections

Another great use of alpha channels is the ability to store more complex selections that would otherwise be difficult or time consuming to recreate again. The Channels panel reports your current pixel selection as a channel entry, so by creating a 'new' Spare Channel from that pixel selection you've stored the selection for future use.

Pixel selections and masks

Because alpha channels store both selection and masks, the Channels panel acts as a great central point for working between masks and selections.

Blend ranges

You can control how specific colour channels of the current layer blend with the underlying layer(s). For more information, see Layer blend ranges.

Editing spare channels

The spare channel that stores your mask can be isolated for editing. This lets you paint and erase directly on the spare channel, as well as apply filters such as Gaussian Blur for softer mask edges.

To create a mask or greyscale layer from a current layer's channel:

-click the layer's channel, then click Create Mask Layer or Create Greyscale Layer.

The new layer is added to the Layers panel.

To invert, clear or fill a layer's channel:

-click the layer's channel, then click an option from the pop-up menu.

To save a selection as an alpha channel:

With a pixel selection in place, -click the 'Pixel Selection' entry and select Create Spare Channel.

The selection is stored at the bottom of the Channels panel as a new 'Spare Channel' entry.

 To edit a spare channel and apply to a mask:

From the Layers panel, select a mask layer.
From the Channels panel, -click the Mask Alpha layer, and choose Create Spare Channel.
 Click on the newly created 'Spare Channel' entry to isolate it.
Edit the spare channel.
Reselect the mask layer in the Layers panel to exit isolation mode.
-click the spare channel and choose Load to Mask Alpha to apply the edited spare channel to your mask.

 Before editing a spare channel, you have the option of duplicating the initial spare channel. This procedure is often used to preserve an unedited backup copy of a spare channel before editing the original.

To duplicate a spare channel:

-click the 'Spare Channel' entry and select Duplicate.

The duplicate is stored below the original as a new 'Spare Channel' entry.

To rename a spare channel:

-click the 'Spare Channel' entry and select Rename.
Enter a new name for the channel, then click OK.