Subtitles of the Movie

To further emphasize and illuminate the distinction between selections and masks, I want to do an exercise to show you something called the 50 percent rule, and also show you how masks relate to selections in more detail. I am going to create a mask from scratch. So I'm going to go to the Channels menu here and go over to the corner pull-down menu and choose New Channel. And I will call this one '50 percent test', and you can see it has created a new blank mask channel right now. With a rectangular marquee selection tool, I am going to create three areas with different fills. The first one I am going to fill with white. So with my selection active on my mask channel, I will go to Edit menu>Fill and one of my options for Use is white. I am going to move this over a little bit, and what I am going to do now is fill this with a middle gray value. And notice when I am editing a mask channel, my color pickers switch to grayscale values, because mask channels do not support color - they only support 256 levels of gray from black to white. So I am going to choose 51 percent gray, and what that is, is 51 percent from white to black or 51 percent white. Edit>Fill and I will choose the foreground color, because that's what I just picked. And for the last rectangle, I'm going to fill that with a gradation from black to white. So, I am going to click on the small black and white icon here, which will immediately make my foreground and background color black and white. Choose Gradient tool, which I will talk about in a later movie, and drag to fill this area from white to black. So here is my new mask with a white rectangle, a gray rectangle and a rectangle filled from black to white. I am going to go back to my RGB apple by clicking on its name, and I am going to load this mask as a selection. Select menu>Load Selection, and the channel I want is the 50 percent test. So I will select that and click OK. Now notice that where I had a white area, I get marching ants around that selected area. Where I had the gray, I don't get any marching ants and the reason is that you only get marching ants in areas that show you a value of 50 percent gray or brighter. This area is actually being selected but only 51 percent or only 49 percent selected. And this value is being selected, you can see, but it stops half way down at about the 50 percent mark. Now I am going to fill my new selection with 100 percent of my blue foreground color. And this will all become clear to you now. Even though I am not seeing my marching ants, this area was affected about 50 percent. And you can see how this area has been affected in a gradated manner. So that's called the 50 percent rule. Any area on a mask which is 50 percent gray or darker when activated as a selection, you do not see marching ants or a selection around it. But when you go to do something such as fill with a color or make some kind of edit, it is selected to the extent that its value is gray in the mask.