In the last column we took a look at past and future topics. This next group of columns will look primarily at methods for local (as opposed to global) image optimization techniques. This column is an initial look at masks, a primary tool for this process.rnThus far, most of our image-optimization steps have been designed to "globally" correct an image. By "global" we mean that the change has been made throughout the entire image. This global approach made sense because most image problems are global, and not local. Figure 1A is such an image. Figure IB is the accompanying Layers palette. Both the Curves layer and the Unsharp Mask layer above it are examples of global correction.
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