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Advanced Blending Options

Opacity got you down? Blend modes just not enough? Why then, you need the Advanced Blending options, a collection of settings so absolutely terrific you'll be reaching for the phone and calling your mother to thank her for giving birth to you (as well you should anyway — mothers work so very hard).

To display the Advanced Blending options, you have three options: First, you can double-click the layer thumbnail. Second, if you want to modify the Advanced Blending options for a specialty layer — such as type or an adjustment layer — right-click the layer name or thumbnail (Control-click on the Mac) and choose the Blending Options command. You can also right-click in the image window with one of the selection tools and access Blending Options that way. Third, you can press Alt (or Option) and double-click the layer name. So you decide.

In any case, you'll see the vast and stately Layer Style dialog box. This one multipaneled window holds controls for adding layer effects, changing the opacity and blend mode of a layer, and achieving some special blending tricks, which I'll be discussing here. By default, you should see the Blending Options panel, pictured in Figure 13-31. If you're working in some other area of the dialog box, click the Blending Options item at the top of the list on the left side of the dialog box.

Figure 13-31: Using the Advanced Blending options, you can turn a layer into a floating hole, make specific color ranges invisible, and more.

You already know how the two General Blending options, Blend Mode and Opacity, work. The same goes for the Fill Opacity slider (though as we'll see, it takes on broader meaning in this dialog box). These are the same options found in the Layers palette and discussed in the first half of this chapter. The next few sections explain the Advanced Blending options, spotlighted in Figure 13-31. Like so many aspects of blend modes, these options can be perplexing at first. But after you get the hang of them, they enable you to gain a degree of control over your layers unrivaled by any other image editor.

Blending interior layer effects

I should say at the outset that the Fill Opacity value behaves exactly like the Fill option in the Layers palette. Enter a number in one option and it appears in the other as well. They are as one. The same goes for the Blend Mode setting in the dialog box and the selected mode in the Layers palette. However, we are about to discover a few ways to modify the performance of the Fill Opacity and Blend Mode options that are possible only from the Advanced Blending options.

As you may recall, the Opacity value controls the translucency of all aspects of a layer, including pixels and layer effects alike. This is a fact of life, regardless of any other settings that may be in place. Meanwhile, the Blend Mode and Fill Opacity settings modify the interaction of pixels independently of most or all layer effects. This caveat, "most or all," is where things get interesting.

You see, Photoshop divides layer effects into two groups that you can control independently of each other. Interior effects fall inside the boundaries of the filled areas of a layer and consist of the Inner Shadow, Inner Glow, Satin, and three Overlay effects. Exterior effects fall either outside or both inside and outside the boundaries of a layer. These consist of the Drop Shadow, Outer Glow, Bevel and Emboss, and Stroke effects.

Using blend modes and Fill Opacity, Photoshop permits you the option of modifying interior effects independently from exterior effects. The catalyst at the heart of this behavior is the check box labeled Blend Interior Effects as Group. When turned off, as by default, blend modes and Fill Opacity affect the pixels on a layer only. But if you turn the check box on, Photoshop applies the blend mode and Fill Opacity to the interior layer effects as well — only the exterior effects remain unchanged.

Figures 13-32 and 13-33 show examples. In Figure 13-32, we see a layer to which I've assigned three interior effects — Color Overlay, Pattern Overlay featuring the Wrinkles pattern (one of Photoshop's defaults), and a thick white Inner Glow — as well as three exterior effects — Drop Shadow, Stroke, and Bevel and Emboss set to a Stroke Emboss. When I lower the Fill Opacity to 20 percent, the pixels that make up the scanned stamp drop away, but the layer effects do not change. However, if I also turn on Blend Interior Effects as Group, Photoshop reduces the opacity of the three interior effects to 20 percent as well. Figure 13-33 shows the similar relationship that exists between Blend Interior Effects as Group and a couple of blend modes, Multiply and Difference. When the check box is off, the interior effects remain unchanged; when the check box is on, the interior effects are treated as just another part of the layer.

Figure 13-32: The results of taking a layer subject to three interior effects and three exterior effects (top), reducing the Fill Opacity value to 20 percent (middle), and then selecting the Blend Interior Effects as Group check box (bottom).

Figure 13-33: Two blend modes, Multiply (left) and Difference (right), when applied to the stamp layer with Blend Interior Effects as Group turned off (top) and on (bottom). The effect is most obvious on the thick Inner Glow, which turns invisible in the Multiply image and inverts colors when set to Difference.

Note, however, that neither Fill Opacity nor blend mode affects the exterior effects under any circumstance. This is a little odd, because some exterior effects fall inside the boundaries of the layer. In particular, the Stroke effect is set to trace the inside of the layer, and the Stroke Emboss covers the stroke. In fact, the only effect that truly exists outside the layer is the drop shadow. However, as far as Photoshop is concerned, an exterior effect is an exterior effect, regardless of where it happens to fall.

Blending clipping masks

Just as you can control whether interior layer effects blend with filled areas of a layer, you can choose to blend the upper layers in a clipping mask along with the base layer or leave them unchanged. By default, the Blend Clipped Layers as Group check box is turned on, thus blending all layers in a clipping mask as a single group. So the blend modes inside the group interact, and then the group as a whole interacts with other layers in the composition. To adjust the blending of the base layer in a clipping mask by its lonesome, deselect the check box. Then, only the Opacity slider will affect the other layers in the group.

For those of you who are thinking, "Yes, that's all very well and good, but what the heck does that gibberish you just wrote mean?" cast your curious eyes to Figure 13-34. Here, I've pasted the happy man on a separate layer, grouped him with the stamp layer so that the man's face falls entirely inside the stamp's edges, and then set the blend mode for the stamp (which is now the base layer for the group) to Hard Light and the Fill value to 50 percent. Using the Blend Interior Effects as Group and Blend Clipped Layers as Group check boxes, I was able to achieve the following effects:

Figure 13-34: After adding a face to the composition and grouping it with the stamp, I set the stamp's blend mode to Hard Light and the Fill Opacity to 50 percent. Then I experimented with turning each of the Blend as Group check boxes on and off.

Both options off: By turning off Blend Clipped Layers as Group, I was able to maintain the happy man's face at the Normal blend mode and full opacity. But because Blend Interior Effects as Group was also turned off, the Inner Glow and other effects wrap around the face, just as they do any other layers in the clipping mask. The result appears at the upper left of the figure.

Interior Effects on, Clipped Layers off: If I turn Blend Interior Effects as Group on, the interior effects — including the Inner Glow and Pattern Overlay — recede behind the clipped face, as in the upper-right image in Figure 13-34. However, exterior effects such as Stroke and Stroke Emboss remain in force.

Interior Effects off, Clipped Layers on: Pictured in the lower-left example of Figure 13-34, this is the default condition for a new clipping mask. The face adopts the blend mode and fill opacity assigned to the stamp layer. The interior effects, on the other hand, remain as opaque as ever.

Both options on: If you want everything to be governed by the base layer of the clipping mask — including clipped layers and interior effects — turn both options on. The result appears in the lower-right example of Figure 13-34.

Masking and unmasking effects

The remaining check boxes — Transparency Shapes Layers, Layer Mask Hides Effects, and Vector Mask Hides Effects — permit you to manage the boundaries of interior and exterior effects alike. These options take us into some weird and rarefied territory. But don't panic. I'm going to briefly explain each one and then walk you through a real-world example.

Transparency Shapes Layer: One of the strangest sounding features in all of Photoshop, turning off this check box deactivates the transparency mask that is normally associated with a layer, permitting layer effects and clipped layers to spill outside the boundaries of a layer to fill the entire image window. If the layer includes a layer mask, effects and clipped layers fill the mask instead. So it serves two purposes: First, you can fill an image or clipping mask with a Color Overlay or other interior effect associated with a layer. And second, you can substitute a transparency mask with a layer or vector mask. I'll be showing both of these in the following pages.

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 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 awful.

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 do.

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.

I have a tendency to make bold pronouncements on the Photoshop features I like and loathe, and the Channels check boxes fall into the latter category. They are, for the most part, useless. There are exceptions, of course — in a CMYK image, it can prove helpful to drop a layer inside, say, the Black channel — but for general RGB image editing, they just don't cut the mustard. Which is too bad, because if slightly retooled, they could. For example, I would very much like to control the translucency of a layer on a channel-by-channel basis, but instead we have only on or off controls. One lives in hope for something better.

Making knockouts

Okay, enough grousing. Back to the good stuff. Like the Knockout pop-up menu.

Knockout turns the contents of the active layer into a floating hole that can bore through one or more layers behind it. It's like a layer mask, except you can use it to mask multiple layers, and their layer effects, at a time. You can also apply layer effects to the knockout, making them extremely flexible.

Creating a knockout is arguably more abstruse than it ought to be, but it ultimately makes a kind of twisted sense. You specify how deep the hole goes using the Knockout pop-up menu. Then use the Fill Opacity or Blend Mode option to define the translucency of the hole. The Knockout pop-up menu provides the following three options:

None: This setting is the same as turning the knockout function off. The layer is treated as a standard layer, not a hole.

Shallow: Choose this option to cut a hole through a group of layers in a set and expose the layer immediately below the set. In a clipping mask where Blend Clipped Layers as Group is turned off, Shallow burrows down to the layer directly below the base layer of the group. When Blend Clipped Layers as Group is turned on, the knockout layer burrows down to the base layer in the group. If the layer resides inside neither a set nor a clipping mask, the Shallow option typically cuts a hole down to the background layer.

Deep: The final setting bores as far down as the background layer, even if the knockout layer resides in a set. A notable exception occurs when working inside a clipping mask. If the Blend Clipped Layers as Group check box is on, Deep burrows down to the base of the clipping mask, just like Shallow.

See, I told you it was abstruse. But in truth, making a knockout has less to do with what option you choose on the Knockout pop-up menu and more to do with Fill Opacity, layering order, and sets. Consider my revolutionary idea in motoring shown in Figure 13-37. Here we have a pair of friendly highway markers that tell you where to go. I call out, "Where's the Garden State?" and they yell back, "You're on it, you knucklehead!" Forget global positioning systems — invest in talking highway markers today.

Figure 13-37: If you're like me, the first thing you do upon arriving in a new city is rent a car and spend a few hours driving around the wrong state, playing the radio too loud and trying to look at an elaborately detailed map while hurtling past one exit after another at 70 miles per hour. Wouldn't it be easier if someone would invent talking highway markers? Here's my sketch, now get on it. Remember, I get 25 percent of net.

I created my brave new vision using vector masks, as I explained a few pages back in the "Masking and unmasking effects" section. If you look closely, you may notice that I replaced the one-time stamp layer with a pattern, threw out the now unnecessary Pattern Overlay effect, and deleted the gradient layer mask (first featured in Figure 13-35). Finally, I added posts behind the signs and set the background image — a photograph of New Mexico's Ship Rock — on an independent layer, so I could reposition it if need be. Okay, so the signs cast drop shadows onto the Ship Rock image — that's not realistic. But bear in mind, it's all conceptual. The real highway markers will be much cooler.

At this point, I decided that these shouldn't be little signs, like the highway markers we see now. They should be great huge things that emerge from the ground like the ancient moai heads of Easter Island. Otherwise, how will you be able to hear them as you speed on by? To do this, I needed the markers to fade up from the ground. For a single sign, I could use a layer mask, but for multiple signs, I needed a knockout layer.

In Figure 13-38, I started things off by creating a new layer and filling it with a slightly angled black-to-transparent gradient. Then I double-clicked the gradient thumbnail in the Layers palette and set the Knockout option to Shallow, which is a good place to start. But nothing happened. That's because you need to follow up by telling Photoshop how transparent to make the knockout. You can do this using a blend mode — for example, setting the gradient to Screen would make the black transparent, thereby cutting a hole. But the most straightforward method is to lower the Fill Opacity value. By reducing the value to 0 percent, I instructed Photoshop to use the filled portions of the gradient layer to burrow through all layers below. (Transparent portions of the knockout layer have no effect.) Note that you have to use the Fill value; the standard Opacity value does not work for this purpose.

Figure 13-38: To mask through the many layers that make up the two signs, I made a new layer and filled it with a black- to-transparent gradient (top). Then I set the Knockout option to Shallow and reduced the Fill Opacity to 0 percent, which masked down to the white background (middle). To constrain the knockout, I combined all layers except the Ship Rock image into a set (bottom).

So far so good, except for one tiny problem: The knockout went too far, masking all the way down to the white background layer, as illustrated in the second image in Figure 13-38. I set the Knockout to Shallow, which is the least amount of knockout I can apply, but without clipping masks or layer sets to guide it, Photoshop goes ahead and drills down to the bottom of the stack. How do I tell Photoshop to drill down to the Ship Rock layer instead? By combining the knockout and the layers I want to mask into a single set.

So I link the gradient knockout layer to the many layers that make up the signs and posts (using the link icons on the left side of the Layers palette). Then I choose New Set From Linked from the Layers palette menu. That's all there is to it. The Shallow setting tells the knockout to bore through to the layer immediately below the set, which is the Ship Rock layer. The result appears at the bottom of Figure 13-38.

After all this work to make a so-called shallow knockout even shallower, why would you ever choose Deep? Because your image may contain a network of layer sets and clipping masks, and you want to cut all the way through to the background. For example, let's say I wanted to create a floating crop boundary. In other words, I didn't want to throw away any background details for good, nor did I want to reduce the size of my image window. I merely wanted to add an empty border around my image to indicate how the final composition should be cropped.

To make my crop boundary, I created a new layer and used the rectangular marquee tool to draw the perimeter of my final image. Then I pressed Ctrl+Shift+I (z -Shift-I on the Mac) to inverse the selection and filled the area outside the crop with black. (Incidentally, I didn't have to use black; any color will do. It's just important to make the knockout pixels opaque.) The first example in Figure 13-39 shows my progress thus far.

Figure 13-39: To establish a floating crop boundary, I created a new layer and filled the area outside the desired crop with black (top). Then I set the Knockout to Deep and reduced the Fill Opacity value to 0 percent. I also added an Inner Shadow effect to the knockout layer, which resulted in what appears to be a drop shadow behind the image (bottom).

To turn the blackness into knockout, I double-clicked the layer thumbnail to bring up the Advanced Blending options, set the Fill Opacity to 0 percent, and set the Knockout to Shallow. The knockout works, but it only goes down as far as the Ship Rock layer. This is because I've gone and created the crop layer inside my new set. So I have two choices: move the crop layer in front of the set, in which case it'll burrow through everything inside and outside the set, or just set the Knockout option to Deep. The latter seemed easier, so that's what I did.

Finally, I decided I wanted my cropped image to have some depth. So I added a drop shadow. However, if I were to apply the Drop Shadow effect, the knockout would cast the shadow into the image. I want the shadow to go into the knockout, so I apply the Inner Shadow effect instead. The final image appears at the bottom of Figure 13-39.

At this point, I could move my crop boundary, add to it, change the effects, or other-wise modify it without worrying about harming a single pixel in the composition. Couldn't I do this same thing by simply filling the crop layer with white, as Photoshop artists have been doing for years? Yes, but there are two benefits to using a knockout layer instead: You have more flexibility where layer effects are concerned, and you can turn around later and composite this cropped image against a different background or frame. Simply put, no other cropping technique is this flexible.