Masking Images with Alpha Channels

JGaulard

Member
Staff member
#1
Alpha channels and masks go hand in hand when it comes to Adobe Photoshop. They're pretty much one and the same. If you aren't familiar with masks, you can read up on them in my "what are masks" post and if you aren't familiar with alpha channels, you can read up on them in my "what are alpha channels" post. In these two posts, I explain everything you'll need to know about these two topics.

In this post, I'll explain why someone would want to create an alpha channel as well as what they might do with one. It's actually a very simple topic, so this shouldn't take long at all.

The reason people create alpha channels in Adobe Photoshop is to save either a selected area or a mask. When working with both masks and selections, you'll find out that they're almost single use sorts of things. When you go into the Channels panel and use the menu in its upper right to select New Channel, you'll have created a new alpha channel that's there to stay. You can use that channel over and over and since you now know what a channel is by reading my post, you can definitely see the benefit of that.

Now let's move onto explaining what someone might do with an alpha channel.

Since an alpha channel is just a mask for channels, and since, after creating it, it's hiding all of the other channels, I could use the Brush Tool set to white to reveal some of the image. This is perfect for when I have areas that I'd like masked or selected and to save those masks or selections for either later or multiple uses. So, I'll paint an area white and that area will be revealed. If I were to head down to the bottom of the Channels panel and click the Load Channel as Selection button, I could turn the area I just painted into a selection. I'd see the marching ants and everything.

Now, the really cool part is that once the selection is made, I could apply an adjustment to that selection by visiting the Adjustments panel and choosing one of the available options, just as if I had created the selection the traditional way. And again, the value in using alpha channels for this process is that you can save them for later use. They don't just go away and disappear once you're finished with them.

For much more thorough coverage of this topic, you can read through my post that I shared just a few days ago. It includes much longer and drawn out commentary as well as screenshots that will help you grasp what I'm referring to. Trust me, this is easy stuff. You just need to try it out for yourself in your own installation of Photoshop to get it.

If you have anything to add regarding Channels in Photoshop, please comment below. Also, if you have any questions, please ask below as well. I'm always here to help. Thanks!
 
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