When we talk about "channels" in the photography and graphic design world, we're referring to the color components that make up an image. So what is an alpha channel in Photoshop? Essentially, it's a component that determines the transparency settings for certain colors or selections. In addition to your red, green, and blue channels, you can create a separate alpha channel to control the opacity of an object, or isolate it from the rest of your image.
Below, we'll show you how to save a selection in Photoshop as an alpha channel, so that dedicated effects can be applied to that area, or so the channel can be read by other applications.
- First, start Photoshop and open the project that you want to edit. Choose the Quick Selection tool from the main toolbar (or press W), and then draw around the desired area until a dashed line appears around it.
- Next, you'll want to save the selection outline so you can use it later. There are a few ways to do this, but the most straightforward option is to find the Select menu on the top bar, and then click "Save Selection".
- In the Save Selection window, you can choose where to save the alpha channel for future use. In the vast majority of cases, you'll want to save it in the current project (this should be the default option), but you can also save the selection in another project if it's currently open and has the same pixel dimensions. Select "New" for the Channel option, choose a name for your selection, and then click OK.
- Now, your new alpha channel will appear in the Channels tab, which is in the same window as your Layers palette. Click on your new channel, and then deselect the area you originally selected by pressing CTRL+D (or Command+D). Once you've created an alpha channel, you don't need to worry about keeping an area of your image selected, because you can always load the channel and make edits from there.
- Take a look at your alpha channel; you'll see that the selected areas are white, while everything else is black. This is true anytime you use the New Selection option. If you zoom into the selected area, you'll also notice that some of the pixels are grey around the edge of your selection. Those pixels are partly selected, and Photoshop does this for anti-aliasing purposes, which helps to smoothen the selected edges.