Static selection vs. dynamic layer mask

- [Instructor] In this movie, I'll show you the difference between working with the static selection outline, which dramatically limits your creative options and a dynamic layer mask which is almost always the better way to go. So let's say I want to select this kitten and I want to move it against these storm clouds, in order to create this final effect here. Alright, I'll go ahead and switch over to the kitten and I'll select it by going up to the Select menu and choosing the Color Range command. Now I could try to select the animal by clicking some place inside of it and then shift dragging all over the place like so.

And eventually, I imagine I would be able to select it. But, because he's set against the white background it's so much easier to just click inside that background in order to select it. Now notice that we're selecting into the highlights in the eyes as well. Now I could increase the fuzziness value in order to create some more natural transitions around the animal, around its fur. But if I do that, I'm going to select even more of its face. So, I'm just going to leave the fuzziness value set to 40. You might wonder why I don't take it down to something lower in order to more or less get rid of these highlights.

But notice if I switch the Selection Preview from None to Grayscale, that we still go ahead and select the highlights, it's just that we have more jagged hair. So we're better off with a fuzziness value of 40. Now of course I want to select the animal and not its background, so I'm going to turn on the invert checkbox like so. At which point, we'll see that there's a few other gray pixels hanging out inside the cat's face, which is ultimately going to be a problem for us. Alright, but there's something I can do about it here so I'll just go ahead and click OK, in order to select that cat.

Alright, now let's say we just want to work with this static selection outline. Then, what you could do is go up to the Edit menu and choose the Copy command. Or of course you have that keyboard shortcut of control C here on a PC or command C on a Mac. Then I'll switch over to the storm clouds image and I'll go out to the Edit menu and choose the Paste command or you could press control V or command V on a Mac. And notice if I zoom out a little bit here that he's not centered and he's also not aligned to the bottom of the canvas. To fix that, I'll press control A or command A on a Mac to select the entire image.

And then I'll switch to the Move Tool at the top of the tool box which I can get by pressing the V key. And now I'll go up to the Options bar and I'll click on this third icon, Align bottom edges, which is going to align the cat to the bottom of the canvas which is exactly what I want. And then I'll click on this Align horizontal centers which should, theoretically, center the cat but it doesn't actually do anything. And that's because of the weird shape of the selection outline. Photoshop has decided it needs to center things between the far left point of the cat in the bottom left corner and the far right point in the top right corner, the top right of the ear, that is, which is not what I want.

So I'll just go ahead and press control D or command D on the Mac and then it turns out that in order to center the animal, I need to press shift left arrow, one, two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15 times and I just happened to know that from experience at which point, he starts to look centered. But, we've got some problems. For one thing, we have these bright fringes around the cat's fur, which don't really match with the background. And then, if you zoom in on the eyes, you can see that we've got problems in both the left and right eyes.

And at this point, because we're working with the static selection outline, we do not have access to those original pixels so there's really nothing we can do. Compare that to what happens if I go ahead and press the backspace key or the delete key on the Mac to get rid of the cat, and I switch back to the original image there. And instead of working with the static selection outline, we work with a dynamic layer mask instead. And we're going to do that just by dropping down to the Add layer mask icon, at the bottom of the Layers panel.

That automatically converts the selection to a mask. So that we can see everything inside the selection and everything outside the selection disappears and turns into this checkerboard transparency. Now notice that Photoshop has automatically converted the background to a floating layer, which it's calling Layer zero. I'll go ahead and rename that layer, cat. And then I'll switch back to my rectangular marquee tool, which I can get of course by pressing the M key. And I'll right click some place inside the image window and I'll choose Duplicate Layer and then I'll change the destination document to storm clouds and I'll click OK.

Alright now if we switch over to the storm clouds document, the cat is aligned to the bottom of the image automatically. And that's because the cat and the clouds are exactly the same height. However, they are not the same width which means I need to center this cat by switching to the Move Tool and then I'll press control A or command A on the Mac to select the entire image. And now notice when I click on Align horizontal centers, everything works out exactly the way it should and that's because Photoshop is smart enough to go ahead and center the full layer instead of just what was formally a selection outline.

Alright so I'll go ahead and press control D or command D on a Mac to deselect the image. And we have the exact same problem by the way, we're missing the eyes as you can see right here. But, we can address that problem by switching to the layer mask. And so you want to just go ahead and click on the thumbnail for the layer mask, here inside the Layers panel. And if you want to see that mask independently of the image, then just alt or option click on it like so. And now, let's just go ahead and zoom out a little bit here and then switch to the rectangular marquee tool and just go ahead and marquee this junk in the center right there.

Make sure that your foreground color is set to white and if it's not, just go ahead and tap the D key and D, as you may recall, stands for default colors. And then press alt backspace here on the PC or option delete on the Mac to fill that selection with white. And now, just go ahead and press control zero or command zero on a Mac to zoom out. And make sure that you don't have any white columns on the left and right sides. If you do, just go ahead and fill those with black. I don't because my background color was by default black in the first place, so everything's looking fine.

Which means I can press control D or command D on a Mac in order to deselect the image. And then, just click on the thumbnail for the cat itself, here inside the Layers panel in order to switch back out and you can see that the face is now entirely intact. And that is a very basic demonstration of why dynamic layer masks are so much better than static selection outlines for all compositing purposes here inside Photoshop.