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Layer Mask Hides Effects: When turned on, this check box uses the layer mask to mask both the pixels in the layer and the layer effects. When turned off, as by default, the layer mask defines the boundary of the layer, and the effect traces around this boundary just as it traces around other transparent portions of the layer.
Vector Mask Hide Effects: As I discuss in the next chapter, Photoshop's shape tools allow you to draw vector-based shapes, which you can fill with flat colors, gradients, patterns, or even layered images. When working inside a layer inside a shape, you can use the Vector Mask Hides Effects check box to specify whether the shape defines the outline of the layer (check box off) or clips layer
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Part IV: Layers, Objects, and Text
effects just as it clips pixels (check box on). For complete information on defining a layer mask, read the "Editing the stuff inside the shape" section of Chapter 14.
Okay, so much for the basics. But why would you ever use these options? The short answer is, because something has gone wrong and you want to correct it. Don't like how your layer effects look? Turn one of these options on or off and see whether it makes a difference. Of course, it helps to have a little experience with these options before you start randomly hitting switches, so let's work through an example.
The top image in Figure 13-35 is basically a repeat of the first image in Figure 13-34 the stamp layer is set to Hard Light with a Fill Opacity of 50 percent. The face layer is grouped with the stamp and both the Blend Interior Effects as Group and Blend Clipped Layers as Group check boxes are turned off. Now let's say I decided to add a layer mask to the stamp layer. Nothing fancy, just a gradient from black at the bottom of the image to white near the middle, as shown in the second example in Figure
13-35. Naturally, this made the layer transparent at the bottom and opaque toward the middle, but it had an unexpected consequence. The mask shaped the boundaries of the layer, giving it a very soft edge that the layer effects didn't quite know how to accommodate. Rather than fading into view, the Inner Glow effect starts abruptly at the point where the layer becomes fully opaque, right under the guy's nose (see the final image in Figure 13-35). As it turns out, it really wasn't the inner glow's fault it was a function of the Stroke being set to Inside but who cares? The plain fact of the matter is, it looks
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Figure 13-35: Starting with the face masked inside the stamp (top), I added a layer mask to the stamp layer using the gradient tool (middle). But instead of fading the effects, the mask shoved the edges of the Stroke and Inner Glow so far upward, I worry that our once chipper fellow may soon run out of breath (bottom).
One's natural proclivity in a situation like this is to say, "Gosh, I guess I can't combine a layer mask with Inner Glow and an inside Stroke effect. I think I'll go soak my head now." But don't drown your sorrows (and head) just yet Photoshop has it all figured out. In the first image in Figure 13-36, I fixed the problem by simply turning on the Layer Mask Hides Effects check box. This way, rather than constraining the effects, the layer mask fades them out just like a good gradient mask is supposed to
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477 Photoshop CS Bible @Team LiB
Figure 13-36: After fading out the Inner Glow and Stroke effects by selecting the Layer Mask Hides Effects check box (top), I turned off Transparency Shapes Layer, which permitted the Pattern Overlay effect to fill most of the image (middle). Then I added a vector mask to the stamp layer and left the Vector Mask Hides Effects check box off, as by default (bottom).
The second example of Figure 13-36 shows what happened when I turned off the Transparency Shapes Layer check box (on by default). Suddenly, the layer effects are no longer constrained by the boundaries of the stamp layer and grow to fill the entire layer mask. Edge-dependent effects, such as Inner Glow, Drop Shadow, and Stroke disappear. Meanwhile, the Color and Pattern Overlay effects expand to fill the image.
Next, I added a vector mask to the stamp layer. To do this, I pressed the Ctrl key (z on the Mac) and clicked the layer mask icon at the bottom of the Layers palette. After selecting the custom shape tool and selecting the highway sign symbol from the Shape menu in the Options bar, I pressed the plus key (+) to make sure the Add to Path Area button was active and drew my shape. Photoshop automatically traced the Drop Shadow, Inner Glow, and Stroke effects around the shape, as in the final example in Figure 13-36. However, if for some reason this weren't to occur, I had only to visit my handy Advanced Blending options and turn off the Vector Mask Hides Effects check box. Dumping whole color channels That takes care of the most complex of the check boxes. All that remain are the Channels options. Located directly below the Fill Opacity slider in the Layer Style dialog box, the Channels check boxes let you hide the layer inside one or more color channels. For example, turning off R makes the layer invisible in the red channel, sending colors careening toward vivid red or turquoise (all red or no red, respectively), depending on the colors in the layers underneath.