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At this point, you should feel very comfortable reading histograms to help assess what corrections are necessary in an image. You should also have a grasp on performing basic contrast and tone corrections using Levels and Curves, and should feel comfortable adjusting some of your own images. Before you head off to your photo archive, though, look at one more example that might save you a little frustration.
As you’ve already seen, you can use Levels, Curves, and Hue/Saturation to adjust the tones and colors in your image. However, it’s important to note that even though Curves provides a lot of flexibility in terms of being able to limit your corrections to a particular color, there will still be times when you cannot set enough control points on the curve to constrain your edit to a particular part of the image.