Just a note. One thing I haven't seen mentioned in this discussion is a hidden feature of Photoshop 6 & 7. When using Levels if an end point slider is moved while the Alt key (Windows) is depressed only the areas being changed are shown. Avery [Non-text portions of this message have been removed]
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Levels vs. Curves - hidden feature of levels
2003-09-30 by Avery Minor