Section 5.7. Things You Can Do to Modify a Layer

5.7. Things You Can Do to Modify a Layer

There are many other ways you can change a layer or the way it affects layers below it.

5.7.1. Use the Merge Visible command

To create a flattened version of a layer, I usually duplicate the image, flatten it, copy the flattened image to the Clipboard, and paste that into the original version so that it becomes its own layer. That's one way to do it, but it's really just an old habit from days gone by. Here's a much more efficient procedure:

1. Highlight the top layer in the Layers palette.

2. While pressing Opt/Alt, choose Merge Visible from the Layers palette fly-out menu. When the new layer appears, it is a flattened version of the whole file.

Just be darned (I'm not allowed to swear) sure that you're holding down Opt/Alt when you do this. Otherwise, you'll flatten your entire image. C'mon Adobe! There's already another command that flattens images. The only thing that requiring the Opt/Alt does is make it possible to mess up. But if you do mess up, don't panic; just press Cmd/Ctrl-Z immediately to undo the foolish thing you just did.

5.7.2. Apply Blend Modes

The Layers palette features 23 different Blend Modes (Figure 5-5). They're called Blend Modes because they cause the layer that's been assigned a Blend Mode to mix its colors with the immediately underlying layer in a specific way.

Figure 5-5. The Layers palette Blend Mode menu.

These are hard to describe, but Table 5-3 shows how the gradient in the Normal mode blends with the image in the upper left corner when each other Blend Mode is applied. Since this gradient contains all of the primary colors, you should get a good idea of what each mode does. However, there's no substitute for good old trial and error. Besides, the actual effect can vary considerably by dragging the Fill and Opacity sliders in the Blend Modes' layer.

Table 5-3. Blend Mode examples

5.7.3. Set the Opacity field/slider

This slider, which is at top left of the Layers palette, always starts at minimum opacity. As you drag the slider to the left, the currently chosen layer becomes more and more transparent. You can also set Opacity to a percentage by entering a number in the field box.

5.7.4. Set the Fill field

At first glance, this slider seems to do the same thing as its older brother, Opacitybut it doesn't. If you set Opacity, you're setting the opacity of the blend mode. If you set Fill, you're setting the opacity of the colors in the fill layer. It's a very thin line, but there can be a very big difference in how Blend Modes treat a layer, depending on what the Opacity and Fill settings are.

5.7.5. Use the History Brush tool

The History Brush is very useful for restoring details from the original once you've imposed a layer effect, filter, or made an Extraction. It paints back either the original state of the image or a History Snapshot. History Snapshots are stored as invisible layers at the top of the History palette. You can create a snapshot at any time by clicking the Snapshot icon at the bottom of the History palette. All the same brush modes and styles that can be applied to the Brush tool can be applied to the History Brush tool.

5.7.6. Employ the Eraser tool

The Eraser can be extremely useful when you're working with layers and blend modes. If you want to "paint in" some transparency into the layer, you can preset the Opacity or Flow (same as Fill for a Layer) of the Eraser Brush. The Eraser can be used as a Brush, Pencil, or Block. In Brush mode, all of the regular brush settings are available to you.

5.7.7. Create a Mask

The Mask icon is at the bottom of the Layers palette. If you click it, it will add a mask to the current layer. If you already made a selection at the time you click the New Layer icon, it will automatically be masked by the selection. In most cases, you will want to "blend" the contents of the selection with those portions of the image that are outside the selection. You do that by choosing SelectionFeather and setting the number of pixels for the width of the feathering stroke. A "feather is simply a black to white gradient that follows the path of the selection and is spread evenly from dark to light. Inside the selection, the mask graduates from black to 50 percent gray, and outside from 50 percent gray to white. In a mask, black is 100 percent opaque, while white is 100 percent transparent. You can see the effect of a feathered mask in Figure 5-6.

Figure 5-6. A mask feathered to 50 pixels.