Layer Mask Essentials


HOW TO APPLY THE CHANNEL PRINCIPLES YOU'VE ALREADY LEARNED TO WORKING WITH LAYERS

You often hear people in Photoshop circles talking about "not bruising the pixels" and "non-destructive editing." What they're basically talking about is protecting the original imagenot doing something you can't easily undo at anytime (and since the History palette only gives you 20 undos by default, it's very easy to run out of undos and do damage).

Well, one of the non-destructive editing methods uses a mask attached to your layer. So, you're never really erasing pixels, you're just hiding them or letting them show (you're either concealing them or revealing them). Luckily, since you've already had some experience with how masks work, you'll be right at home with these "other" types of channels (they're not really channels at all, but they act like them in many ways, so once you understand channels, using layer masks becomes almost second nature).

Step 1.

OPEN A PHOTO THAT NEEDS SOME EXPOSURE ADJUSTMENT (THE BACKGROUND IS TOO LIGHT)

Here's a photo that has some exposure problems. The girl (my sweet, little niece Jenna) is a little overexposed (too light), but the background behind her is even more overexposed. Ideally, you'd darken the background quite a bit, and darken parts of her (like her jacket and maybe her hair), but I'd pretty much leave her face as is. This is where layer masks come in really handy, because they can let you selectively "paint with light" so the image winds up being lit (exposed) just the way you want, right where you want it.

©SCOTT KELBY

Step 2.

DUPLICATE THE LAYER AND CHANGE THE BLEND MODE TO MULTIPLY TO DARKEN

To do a quick fix on the background, press Command-J (PC: Control-J) to duplicate the Background layer, and then change the layer blend mode to Multiply. This has a multiplying effect, which makes the entire photo darker, as you can see here. Now the background looks much better, but her face looks too dark, and even her coat and hair are a bit too dark, as well. So, before we were overexposed (too light), and now our subject is underexposed (she's too dark). Next, we'll add a layer mask so we can have the best of both worlds.

Step 3.

ADD A LAYER MASK TO YOUR DARKENED LAYER

To add a layer mask to this layer (which is kind of like adding a channel to your layer, as you'll soon see), click on the Add Layer Mask icon at the bottom of the Layers palette (circled in red here). This adds what looks like a white Alpha channel to the right of your layer's thumbnail image (as shown). At this point, it has no effect on the photo whatsoeverit's just sitting there waiting for you to do something.

Step 4.

PAINT IN BLACK OVER HER FACE TO CONCEAL THE DARKER VERSION OF HER FACE

On the top layer, we have a darker version of the photo. Directly under it is the original "better exposed" version of Jenna on the Background layer, right? Without a layer mask, we could just grab the Eraser tool (E) and erase over Jenna's face, revealing the better exposed version on the layer below. The problem with doing that is, you're actually erasing pixelscutting a hole out of a photo. However, by adding a layer mask, you're only knocking a hole out of the masknot erasing her photo (like painting in black on an Alpha channel), so you can always undo by painting in white. So, get the Brush tool (B), make sure your Foreground color is set to black (press X), paint over her face, and it reveals the lighter version.

Step 5.

DELETE THE MASK SO WE CAN TRY SOMETHING DIFFERENT

That's one way to do it, but there's a method of applying layer masks that I greatly prefer for this type of "painting with light" technique because you'll usually wind up doing less painting. So, to try this other method, you have to first remove the layer mask we added in the last step. To do that, click directly on the white layer mask thumbnail, and drag it directly to the Trash icon at the bottom of the Layers palette. This will bring up a dialog asking if you want to delete the layer mask or apply it. In this case, you want to delete it so we can start over, so click the Delete button. By the way, clicking the Apply button makes the changes you just made using the layer mask permanent.

Step 6.

NOW FILL THE MASK WITH BLACK, WHICH CONCEALS THE DARKER VERSION BEHIND THE MASK

Now, let's start over. You should still have the duplicate layer in Multiply mode in place, so the photo looks too dark, right? Right. Next, press-and-hold the Option key (PC: Alt key) and click on the Add Layer Mask icon (as shown here). This adds a layer mask to your layer. But if you look at the capture shown here, holding that key down before you clicked the Add Layer Mask icon does two things: (1) the layer mask appears in black, rather than white, and (2) since it appears in black, the mask covers the darker version of the photo, so the photo looks like it did when you first opened it. The darker layer is still there, it's just hidden behind that black mask. That's a good thing.

Step 7.

PAINT OVER THE BACKGROUND IN WHITE TO REVEAL THE DARKER LAYER IN JUST THE BACKGROUND

The reason it's good is that we can now "reveal" the dark parts of the photo right where we want them. So, grab the Brush tool, press X to set your Foreground color to white, and start painting over the background areas of your photo (as shown here). As you paint in white, the background becomes darker, because you're revealing the darker version of the photothe one that's hidden behind that black mask. Think of it this wayblack conceals the darker version of the photo, and white reveals it. It's easy to remember if you use the famous old saying "Black conceals; white reveals." I don't know who said that first, but it does stick with ya.

Step 8.

LOWER THE OPACITY OF THE BRUSH TOOL SO WE CAN DARKEN CERTAIN AREAS JUST A LITTLE

Remember back in Step 1, when I mentioned the two things wrong with this photo: (1) the background was quite overexposed, and (2) Jenna's coat and hair were a little overexposed. Well, we fixed the background, but how do you fix her coat and hair "just a little?" You start by lowering the Opacity of the Brush tool (up in the Options Bar, as shown here). That way, when you paint, it doesn't reveal the full darker version of the image, it only reveals 40% of the strength of that darker layer.

Step 9.

PAINT OVER HER COAT AND OTHER AREAS THAT YOU WANT TO BE JUST A BIT DARKER

Now, you can start painting over her coat (as shown here) and her hair, and as you paint, those areas get a little bit darker. If you want some areas a lot darker (but not fully as dark as the multiplied version of the layer), you can increase the Opacity of the Brush tool.

Step 10.

OPTION-CLICK (PC: ALT-CLICK) ON THE MASK THUMBNAIL TO SEE JUST THE MASK ITSELF

Want to see what you've been up to? Remember how I said when you paint on a layer mask you're not erasing pixels? You're not damaging the image, instead it's like you're working on an Alpha channelyou're painting on a mask, not the original. So, if you ever want to see a glimpse of that mask you've been painting on, just press-and-hold the Option key (PC: Alt key) and click directly on the layer mask thumbnail (as shown here). This shows you just the layer mask itself. The black parts mask the darker version. The gray areas are where I painted in 40%, and that really light gray area is where I painted over the same area twice.

Step 11.

NOW CLICK BACK ON THE PHOTO THUMBNAIL TO RETURN TO NORMAL

To return to the photo, click directly on the thumbnail for the photo (as shown here). Now, it's time for a warning. When you click on a photo's thumbnail (like you just did), you target the photo itself. So if you paint now, it will paint directly on the photo itselfnot on the layer mask. To begin painting on the mask again (revealing and concealing), you'll need to click on the layer mask thumbnail instead. So, that's the basics. I use a similar technique for sharpening portraits, as you'll see at the end of the next tutorial.



The Photoshop Channels Book
The Photoshop Channels Book
ISBN: 0321269063
EAN: 2147483647
Year: 2006
Pages: 82
Authors: Scott Kelby

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