Real World Adobe Photoshop CS5 for Photographers: Using History to Mix Adjustments
From the book
A more free-flowing, seat-of-the-pants alternative to layers is the History panel. History does a lot more than give you as many as 1000 levels of Undo. When you use the History Brush together with edits such as filters or blending modes, you can apply effects that are very similar to those you can achieve with layers and masks. It helps to be familiar with how the History panel works. For that, see "History Panel Tips" in Chapter 6, "Essential Photoshop Tips and Tricks."
You can think of History states as layers in time or frames in a sequence, instead of as a stack of structural layers in the Layers panel. Instead of painting masks to combine layers, you paint parts of one History state into another (see Figure 8-24). But let's look at the important ways in which History Brush painting differs from using layers and masks:
- History is available only as long as your file is open. Once you close the file, its history is gone forever, so you have to get your edits right before you close. (In General Preferences you can turn on a History log, either in the file's metadata or in a text file, but the log doesn't let you apply the logged states.)
- History is easier to use than layers when you know exactly what you're doing and can get things right on the first (or possibly second) try, but if you're less decisive than that, it quickly becomes more work than using layers to achieve the same effects. On the other hand, layers require some advance planning and organization, and if that doesn't fit your creative personality, you may find History more fluid and natural.
- With large files, history can be just as demanding on your hardware as adjustment layers. It requires plenty of scratch space and a fast disk.
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Figure 8-24 Using History to combine different edits
Nevertheless, History is a powerful feature for making edits that are quick, but not dirty.
Applying History. You can apply History using either the History Brush tool or by choosing Edit > Fill. Fill is easier to use when you have a selection or you want to affect the entire image. The History Brush is useful for brushing in edits. When you use either one, you can immediately use the Fade command (on the Edit menu) to adjust the edit's opacity (and hence its strength).