Floating Neutrals
In many cases, you can avoid introducing a color cast into your image by using a floating neutral instead of the RGB or CMYK master curve. Besides, it's fun to move one curve and have the other two curves move along with it.
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Using a floating neutral is as easy as setting a neutral point, as described in the previous session, and moving the resulting curve point on the one of the color channels of RGB, CMYK, or wgCMYK vertically. As if by magic, the corresponding neutral points on the other two curves will move vertically - voila, a floating neutral, and we are rewarded with a nice, almost Lab-like stable shade of orange in the box to the left.
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 Figure 1. A floating neutral moved upward until the image almost explodes. |
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 Figure 2. The floating neutral moved to greatly darken the imge. Note the good stability of the orange hue of the cardboard box. |
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There are at least two new uses for this. First, you now have an alternative to using the RGB, CMYK, or wgCMYK master curves, which are prone to adding unwanted color casts where you least expect it.
Second, you have a way to juggle curves a bit when you want to change the shape of a particular curve, while maintaining two neutrals. Floating neutrals make this 10 times easier, which means you are about 10 times more likely to get a better result.
