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Throughout the series, I use alpha channels quite a bit. I want to go in here and explain to you what exactly an Alpha Channel is. First, what are the Channels? Well, right here, we are going to see this, and we have the Red Channel, it shows you the red components of that image, the greens, and the blues. Now, we are seeing them in black and white, we can see them in color, but it is important to see them in black and white because there are certain different gradiations of a particular tone. You see that, it is blue.
Now, that particular pixel right here, we are going to go in there and select that little tiny pixel right there. That little composite pixel is a certain value of the red. There is no green in it, there is the red, the red and blue, there was no green. But the result is that green right there. So now, each one of these channels is an 8 bit channel, which has 256 colors. So, there are 256 variations for that 1 pixel that we are seeing right there.
The number of value for the red, and the green, and the blue mix will give you that particular color. If we were to bring up our Info window here, we would see that there is the RGB that we will see that, that particular pixel right there is 0 red, 122 green, and 255 blue. So, that's what the Channel will do, gives you your color. Now, Alpha Channels are a whole another animal. An Alpha Channel is not part of the image.
In fact, there are no alpha channels until you create an Alpha Channel. If I go in here and create an Alpha Channel, right now it's going to be completely black. So, what exactly is happening in an Alpha Channel? An Alpha Channel is also an 8-bit channel if you are working in an 8-bit file, and it has 256 levels. But there, those levels have a whole different function. In the color channels, those levels will determine what the end result color will be. But in an Alpha Channel, you are selecting. You know what a selection is? If I go in here, and I select right here, and select this little area of my image, and I start to draw, you know that anything that I do, let's get a nice big brush is going to happen only inside that area.
See, it happens only inside there because by selecting it, I have segregated that area from the rest of the image. When I deselect it, it's gone. I can undo, and say yeah, there it is. But if I have done something else, that selection is gone. If I come back tomorrow, or next year, and open this file, that selection is gone. But when I have something selected like this circle, and I say Save the Selection, and I can call it anything I want. I will say circle.
Now, I can deselect it. Did it do anything to my image? No, but when we go look our channels, there is the circle. And you'll notice that the area that was selected is white, everything else is black. The way an Alpha Channel works is where things are white, they are selected, where they are black, they are protected just like the regular selection works. But it is an 8-bit channel, so there are 256 levels. You go from zero black, to white, which is 255, with 254 levels of gray in between, which will determine how something is selected, giving you much more control on how something is going to be selected in order to be modified.
So, let's go back to our color channels here and look at our layers, let's turn this guy off, and we have a little rod here. This rod is going to be casting a shadow which right now we don't have a shadow. I have a path right there for my shadow, and in that layer for the shadow right there, I am just going to go ahead and fill that with black. And there is my nice long shadow. Now, I am going to go in there, and I am going to bring down the opacity, so it starts to look more like a shadow. Now, I can soften it up, I am going to go in there and give it a little Gaussian Blur just to soften my shadow up just a little bit.
But if you look at reality and the way things work, you notice that a long shadow like this is going to get softer as it gets further back. It's going to get a little more blurred out, sometimes a little stretched out. It needs to be gradually getting softer as it goes back in space. That's where the Alpha Channel comes in, because I can control how something is going to happen. And that something can be anything from a colorization, a filter application, even a pace through, anything can be done through a specialized selection of the Alpha Channel.
So, what I am going to do here is I am going to go in, and remember that first Alpha Channel that I created, it's blank. I want to see the color on top so I can control exactly where my gradient is going to work. I want to blur this much stronger as it gets further away way out here leaving this area alone. So, I am going to get my Gradient tool, set it to Black to White, make sure it's a linear gradient, and down here is where it's going to be protected, right? Back here is where it's going to be exposed.
So I am going to start my black here, because black protects, white exposes, and I am going to draw my line how I want it to work. Just like that. Now, if we look at just the Alpha Channel, you see there is my gradient. Here, nothing is going to happen, here everything is going to happen, through these grays, it's going to happen based on that level of gray. So, I come back to my art, and I load that Alpha Channel. It's showing me my selection from the 50% gray to white. I am just going to go in there and hide those marching ants, so we have a nice blank slate to work with.
Now, I am still in the shadow layer here, I am going to blur it again. So, I am going to give it a Gaussian Blur, and this time I am going to increase it a little more like that. Now, you notice how it's getting blurrier out there. Now, I am going do this in steps because if I apply a large blur, it's going to really look weird. So, I am going to apply it a few more times. You notice how each time, the outside area here is becoming more blurry than down here where it's not becoming blurry at all. Each time I apply it, it gets softer and softer.
So now it starts to take on the look of a true shadow. And that's what an Alpha Channel can do, it allows you to control a selection and how that selection is going to affect the image. It itself is not part of the image, it is simply a way through which you apply effects to an image in a controlled fashion.
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