Layer Clipping Groups
Before I talk about the next two options in the advanced blending section, I need to provide some background information on the subject of layer clipping groups. A clipping group consists of two or more layers that are grouped together and "clipped" by the bottom-most layer in the group. This clipping term just means that all the layers in a clipping group take on the shape of the bottom layer in the group. To give this a try, make the car layer active and, from the main menu, choose Layer, Group with Previous. This creates a layer clipping group consisting of the car and clouds layer. Because the clouds are the bottom layer in the group, the car layer is "clipped" to the shape of the clouds layer. Notice that the thumbnail of the car layer is indented and that a small arrow icon points down to the layer below, to indicate that it is grouped with the clouds layer. (See Figure 12.)
Figure 12 A layer clipping group consisting of the car and clouds layers. The car layer is grouped to the clouds layer and is "clipped" to the shape of the clouds layer.
A handy shortcut for this is to hold down the Alt key (PC) or the Option key (Mac) and place your cursor on the border between two layers. You will see an icon appear that looks like two circles merging (see Figure 13). If you click when you see this icon, you will either create a clipping group by grouping the two layers, or, if they are already grouped, ungroup them.
Figure 13 Alt-click (PC) or Option-click (Mac) between two layers to group or ungroup layers.
Layer clipping groups are an easy way to create shapes from layers without having to make a precise mask. You could use a clipping group to quickly fill a logo or some text with a photo or a texture, for example, without having to actually change the pixels of the logo. Take a look at Figure 14 to see an example of this.
Figure 14 Another example of the possibilities offered by later clipping groups.
Clipping Group Blending
The default behavior for the way a layer clipping group blends is that all of the layers in a group take on the blending effect of the bottom-most layer. To see this in action, set the blend mode for the clouds layer to Difference. As you can see in Figure 15, the car layer is taking on the Difference blend mode because it is part of a clipping group with the clouds layer.
Figure 15 When clipped layers are blended as a group, all the layers take on the blending mode of the layer they are grouped with.
Next, double-click the clouds layer and, in the Layer Style dialog box, uncheck the option Blend Clipped Layers as Group (see Figure 16). This separates the blending of the car and the clouds layer.
Figure 16 When the option Blend Clipped Layers as a Group is turned off, all the layers in a clipping group retain their individual blend modes.
Blend Interior Effects as Group
This setting controls the blending of interior layer effects such as satin, inner glow, pattern, color, and gradient overlays. Normally, layer effects are not altered by a layer's blending mode. The Sunday Driver layer has some layer effects applied to it. If you set that layer's blending mode to Difference, there is no change in the appearance of the layer because the interior gradient overlay effect takes precedence and is not affected by the layer's blend mode. Double-click the layer to open the Layer Style dialog box, and click inside the check box for Blend Interior Effects as Group. This combines the effects with the layer and then applies the blend mode (in this case, Difference) to the layer and its effects. (See Figure 17.)
Figure 17 The Blend Interior Effects as Group setting applies a layers blend mode to any interior layer effects. Normally these effects are not altered by layer-blending modes.