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Figure 10.11 This car is an unusual color, heavily negative in the A channel but near zero in the B. The lack of range in the B creates a problem when switching to a color with extreme values in the B, such as orange.

Saving a Blending Options Mask

Occasionally it is desirable to create an editable mask based on what has already been accomplished with Blending Options, so that it can be retouched and loaded as a selection or layer mask.

To do this, make flattened copies of the original and of the version with the Blending Options. Convert both to RGB and apply one to the other in Difference mode, which creates black areas wherever the two are iden-tical—namely, everywhere except where the Blending Options are taking effect.

Inset is Figure 10.7 applied to Figure 10.9C in Difference mode. To make a mask of it, you can either convert it to grayscale or steal one of the RGB channels. Either can be saved as an alpha channel or a separate file.

layer mask, locate any areas where objectionable parts of Figure 10.8 remain (gross gloppy green blotches in the face would be an example of something considered objectionable), and, with background color in the toolbox set to black, either erase them or lasso and delete them.

Next to Figure 10.10C is a flat swatch representing Photoshop's CMYK rendition of PMS 168. The question of whether the final jacket matches that color sufficiently closely is highly subjective. If you want to change it, it's not too late. The adjustment layer curves still exist. For example, if you feel that the jacket is too red, you could shove the inverted A curve slightly to the right without affecting anything else in the picture.

When the Colors Aren't Opposites

Changing a red car to a green one, or a yellow train to a blue one, avoids a problem that we now need to confront. The green car was the direct opposite of the red one in the A channel, and the B wasn't touched. The blue train was created mostly by inverting the B, coupled with a move of no great importance in the A.

Changing a light green jacket to a brown one requires moving both channels, but it's easier to make duller colors out of brighter ones than the other way around. It's much harder to tr y changing to a bright color that is not close to the direct complement of the original.

As noted in the "Closer Look" section of Chapter 4, the LAB "green"—a strongly negative A channel with the B near zero—is comparatively rare. Almost all things we think of as green, such as the green car of Figure 10.1 B, are in fact strongly to the yellow side in the B. The old car in Figure 10.11, which I'd describe as teal, is, I think, the only example of "LAB green" in the book.

If the assignment were to change this car to magenta, the direct opposite of green, it would be Figure 10.1 all over again. Irritatingly, the client chooses something else, an orange, PMS 7409.

The drill is familiar. The control point shown measures 74L(29)A(5)B. We learn that PMS 7409 is 76L18A78B.

The curves for the first two channels pose no problem. The two L values are almost identical. The A needs to be inverted and flattened, along the lines of the B curve in Figure 10.5. But this car has a better

Figure 10.12 The desired color requires an extremely positive B channel, but the original B measures almost zero. Top, the B channel is replaced by a copy of the A, which is more positive. Below, after the curves at right are applied to the top

Figure 10.12 The desired color requires an extremely positive B channel, but the original B measures almost zero. Top, the B channel is replaced by a copy of the A, which is more positive. Below, after the curves at right are applied to the top

Figure 110.13 The progression of excluding the background of Figure 10.12B. Top, working on the topmost of three layers, sliders limit the scope of the L channel. Center, the B sliders are added. Bottom, additional Blending Options are added to the middle layer, excluding areas that were originally more yellow than blue.

chance of winning the Indianapolis 500 than we do of changing (5)B to 78B with a curve. Making objects twice or even three times as colorful as they were is easy in LAB. Making them 25 times as colorful is another story. The original B channel is too flat to have any hope of creating something as extreme as that yellow. Now, if only it had started out at (28)B rather than (5)B, then we might have a chance. Since the AB channels contain color only and no detail, they can absorb a lot of punishment. One can even be replaced with the other! Figure 10.12A has a copy of the A where the B used to be.

It's important that this replacement take place on a duplicate layer, leaving the original untouched. Can you foresee why?

Now that there's a serviceable B, we add a curves adjustment layer. The file now has three layers, unlike the previous examples, which had only two. The curves that produced Figure 10.12B require little comment.

We proceed to the selection step, activating the Blending Options on the third layer, under somewhat of a handicap. As the L channels of the second and third layer are nearly identical, it won't matter whether we use the This Layer or Underlying Layer slider. In the B

Figure 10.14 The final version, with certain areas of the background eliminated with a layer mask. Left, aflat swatch of the desired PMS orange.

we want to use This Layer, because its range has been enhanced with the curves.

Putting a Blend If on the A, however, is a waste of time. Remember, the B is now an enhanced copy of the A. Anything this A slider can do can be done better in the B. So we operate with two sets of sliders only. For that matter, we shouldn't expect much from the L. Anything lighter or darker than the car won't be as yellow, so the B slider alone should exclude it.

When Three Layers Are Needed

We start by double-clicking the top layer to bring up the Layer Style dialog that contains Blending Options. Figure 10.13A demon-

strates that, as we surmised, working with the L slider does almost no good. It's picked up some dark areas of the background trees, and that's about it.

Going to the new B channel helps a lot. The entire bottom half of the car in Figure 10.13B has cleared the background; no selection will strates that, as we surmised, working with the L slider does almost no good. It's picked up some dark areas of the background trees, and that's about it.

Going to the new B channel helps a lot. The entire bottom half of the car in Figure 10.13B has cleared the background; no selection will

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