Subtitles of the Movie

You might hear the term Alpha Channel, whether you're working in Photoshop or even in a 3D application. An alpha is simply a word that describes the transparency of an image. For example, in a lot of video games you might think that you're seeing a fully modeled leaf, but it's actually just a square that has alpha information on it that tells the 3D application which parts of that image to hide so that we see the outline of a leaf, but it's actually a square with transparency on it. So let me show you where the Alpha Channel lives. By the way, an alpha channel is something we've actually created and you might not have been aware of it whenever we make a selection with one of these tools here. So I'm going to go to my Layers here and I'm going to turn off the Channels so we could just focus on that. Here we have our color channels and if I create a New Channel by clicking this button here, or if I create a Selection, and I save that selection by going to select Save Selection, I'll just call it Shape, notice that it appears here in the Channels. This Alpha Channel tells the application what parts of the image to protect and what parts to have exposed. So if I grab my brush and I try to paint in this Alpha Channel see what happens? I can paint inside where you see white, and the black area I can't paint in. So how useful is this? Well, I'm going to delete this channel and I'm going to delete my selection by pressing Command or Control D. I'm going to create a brand new Alpha Channel manually by clicking on this icon to create a brand new channel and it says Alpha 1. Now what I'm going to do is I'm going to do the old fashioned trick by using the Gradient to show you how to apply an effect to only a portion of your image. So with my Gradient I'm going to click and drag diagonally inside of the Alpha. Now what I'm going to do is I'm going to activate that channel by clicking this icon. Then I'm going to go and turn everything back on and return to my Layers here, and let's go ahead and tuck away the Channels. Now, what I'm going to do at this point is I'm going to apply a special effect. So I'm going to go to Filter, Blur, Gaussian Blur, click OK, and then I'll go ahead and hide my other ones that I added earlier. You'll notice that the blur only occurs in the unprotected parts of the image because the Alpha dictates what parts of the image to save from the effect. So if I go ahead and add the Gaussian Blur and change it a little bit, you'll see that I can play around with the Modes but the strength of it is only affected on part of the image and not the whole thing. That is the beauty of using Alpha Channels. Also what I can do to see exactly the effect is I can click on the eyeball here. The eyeball shows me what parts will be affected the most and what parts will be protected. So if you really ever have any doubt just look at the red to white in your gradient. You can always hide and show and Alpha, and of course you can get rid of it if you want to.