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Dropping Out and Forcing Through
Found at the bottom of the Blending Options panel of the Layer Style dialog box, the Blend If slider bars rank among Photoshop's oldest and most powerful compositing capabilities. Pictured in Figure 13-40, these options enable you to drop out pixels in the active layer and force through pixels from lower layers according to their brightness values. You can even use them in combination with the Knockout option. For example, if you set the Knockout to Deep, you force through pixels from the background layer instead of from the layer immediately below the active layer.
Figure 13-40: Little Puppet Friend ranks the Blend If slider bars among Photoshop's most powerful capabilities, and I'm forced to agree.
Here's how the three Blend If options work:
Blend If: Select a color channel from the Blend If pop-up menu to apply the effects of the slider bars according to the contents of a single color channel. If you choose Gray, as by default, Photoshop bases the changes on the grayscale composite. Each time you select a different Blend If option, the slider triangles change to the positions at which you last set them for that color channel. Regardless of how you set the sliders, Photoshop applies your changes evenly to all channels in the image; the selected channel is merely used for the calculation.
This Layer: This slider bar lets you exclude ranges of colors according to brightness values in the active layer. You exclude dark colors by dragging the black triangle to the right; you exclude light colors by dragging the white triangle to the left. In either case, the excluded colors disappear from view.
Underlying Layer: The second slider forces colors from the underlying layers to poke through the active layer. Any colors outside the range set by the black and white triangles will not be covered and are therefore visible regardless of the colors in the active layer.
Preview: Don't forget to select the Preview check box on the right side of the Layer Style dialog box so you can see the effects of your modifications in the image window every time you adjust a setting.
These options are far too complicated to fully explain in a bulleted list. So I invite you to learn more by reading the following sections. You'll be glad you did.
Color range slider bars
To demonstrate the Blend If options, I've taken the sculpted face and tranquil background composition introduced in Figure 13-7 and added an oldie but goodie element from Photoshop Bibles of yore, The Thinker. (For you longtime readers who might be saying, "Oh no, not The Thinker again! Retire that guy already!" notice that this time, he's facing a different direction. I used to flip him so he was facing right, but this time I kept him facing left, just as photographer Wernher Krutein shot him. No, that's okay, no need to thank me. Putting a smile of genuine satisfaction on a loyal reader's face is reward enough for me.) As shown in Figure 13-41, The Thinker includes a soft drop shadow to distinguish him from the rest of the composition. Like all layers in this composition, he rests contemplatively behind a thin veil of the Blistered Paint pattern set to the Overlay blend mode at 20-percent Opacity.
Figure 13-41: Photoshop Bible regular and Corbis Royalty Free stock image, The Thinker joins the composition for this special demonstration of the Blend If slider bars.
The first Blend If slider bar, This Layer, hides pixels in the active layer according to their brightness values. You can abandon dark pixels by dragging the left slider triangle and abandon light pixels by dragging the right triangle. Figure 13-42 shows examples of each:
Figure 13-42: Examples of modifying the blend mode and This Layer settings in the Layer Style dialog box. The final image shows the copy of The Thinker that I set to Multiply layered in front of the copy set to Screen to get a high-contrast effect.
To create the first example in Figure 13-42, I first set the blend mode to Screen. Then I dragged the black slider triangle until the value immediately to the right of the words This Layer read 130, thereby hiding all dark pixels whose brightness values were 130 or lower.
To create the second example, I changed the blend mode to Multiply. I reset the black slider triangle to 0 and dragged the white slider triangle to 175, which hid those pixels with brightness values of 175 or higher.
The final image in the figure shows the second Thinker layered in front of the first. With the help of the This Layer slider bar, I can combine the Screen and Multiply blend modes to produce an image that is both lighter and darker than its background.
Drag the triangles along the Underlying Layer slider bar to force pixels in the underlying layers to show through, again according to their brightness values. To force dark pixels in the underlying image to show through, drag the black slider triangle; to force light pixels to show through, drag the white slider triangle.
Here's how I achieved the effects in Figure 13-43:
Figure 13-43: Here I changed the Underlying Layer settings to force through the darkest (top) and lightest (middle) pixels from the sculpted face and tranquil background layers. The third image shows the two effects combined.
To achieve the effect in the top example of Figure 13-43, I started off by applying the Linear Light blend mode. Then I dragged the black slider triangle until the first Underlying Layer value read 130. This forced the dark colors in the sculpted face and tranquil background with brightness values of 130 or lower to show through.
In the second example, I changed the blend mode to Luminosity. Then I restored the black Underlying Layer triangle to 0 and dragged the white triangle to 175, uncovering pixels at the bright end of the spectrum.
The final image shows the two effects combined, one copy of The Thinker in the Linear Light mode with Underlying Layer values of 130 and 255, and another in front of that set to Luminosity with Underlying Layer values of 0 and 175. The right eye from the sculpted face blends in with The Thinker's face like another one of his tattoos.
Bear in mind, like every other adjustment made in the Layer Style dialog box, changes made to the Blend If slider bars are temporary. These options hide pixels; they don't delete them. As long as the layer remains intact, you can revisit the Blend If sliders and restore hidden pixels or hide new ones.
Fuzziness
The problem with hiding and forcing colors with the slider bars is that you achieve some pretty harsh color transitions. Although printed at high resolutions, both Figures 13-42 and 13-43 exhibit occasional jagged edges. Luckily, you can soften the color transitions by dropping and forcing pixels gradually over a fuzziness range, which works much like the Fuzziness value in the Color Range dialog box, leaving some pixels opaque and tapering others off into transparency.To taper the opacity of pixels in either the active layer or the underlying image, press the Alt key (or Option on the Mac) and drag one of the triangles in the appropriate slider bar. The triangle splits into two halves, and the corresponding value above the slider bar splits into two values separated by a slash, as demonstrated in Figure 13-44.
Figure 13-44: Alt-drag (Win) or Option-drag (Mac) a slider triangle to split it in half. You can then specify a range over which brightness values will fade into transparency.
The left triangle half represents the beginning of the fuzziness range — that is, the brightness values at which the pixels begin to fade into or out of view. The right half represents the end of the range — that is, the point at which the pixels are fully visible or invisible. Figure 13-45 shows a bit of fuzziness applied to the This Layer slider. Here are the specifics:
Figure 13-45: By Alt-dragging (Win) or Option-dragging (Mac) a This Layer slider triangle, you can create gradual transitions between the opaque and transparent portions of a layer.
In the top example, I set the blend mode to Screen. After splitting the black slider triangle by Alt-dragging (Option-dragging on the Mac), I set one half of the triangle to 40 and the other to 220. Colors with a brightness value of 40 or darker turn transparent, fade into view from 41 to 219, and become opaque from 220 on up.
In the second image, I selected the Multiply blend mode and restored both halves of the black triangle to 0. Then I Alt-dragged (or Option-dragged) the white triangle to split it. I moved the left half of the split triangle to 20 and the right half to 190. The result is an extremely gradual drop off. Those few pixels with brightness values from 0 to 20 are opaque, the pixels from 21 to 189 become gradually translucent, and pixels of 190 and brighter are transparent.
Finally, I combined both effects on separate layers, with the Multiply effect on top. As shown in the bottom example in Figure 13-45, the result is a perfect blending of Multiply and Screen, with the background images showing through in the midtones.
Using the Underlying Layer slider is a bit trickier. It typically works best when you're trying to force through very bright or dark details, such as the highlights in the sculpted face or the shadows in the mountains. It also helps to work with a foreground layer that has lots of flat areas of color for the background to show through. Here's what I did to create Figure 13-46:
Figure 13-46: After combining a High Pass effect with the Linear Dodge and Multiply blend modes, I used both the This Layer and Underlying Layer slider bars to drop out fore- ground colors and force through background colors. In the end, I was able to bring out some interesting details from the Michelangelo sculpture and mountain range.
For starters, I applied Filter Other High Pass to The Thinker layer. As shown in the first example of Figure 13-46, this created lots of gray areas that would serve as ample neutral ground for the Blend If slider bars.
I next applied the radical Linear Dodge mode to this layer. I first dropped out most of the dark colors in The Thinker layer by setting the halves of the black This Layer triangle to 80 and 230. Then I split the black triangle for the Underlying Layer slider, leaving the left half at 0 and moving the right half to 190. This forced through virtually all of the darkest pixels from the rear layers, fading them out as they got lighter.
Finally, I duplicated the layer, applied the Multiply mode, and reset the black triangles to 0. I experimented with the white triangles, ultimately setting the This Layer halves to 110 and 180 and the Underlying Layer halves to 90 and 200. The result is a vibrant composition that contrasts elements of the sculpted face with the outline of The Thinker.
