Now, select Image Adjust Hue/Saturation from the menu. In a nutshell, hue controls the tint of the colors in the image, while saturation controls purity and lightness controls brightness. Primarily, you'll be focusing on altering the saturation of you image to liven up dull colors. Lightness shouldn't be confused with brightness, covered above. Lightness is similar to brightness, covered above, but instead of producing pure white at 100%, lightness produces pure white in areas of the image with lightness of 50% or more. What this means in practice is that by increasing lightness, you increase the brightness of the bright colors. If you still don't get it, play around with the setting and you'll get the idea.
Changing the hue of an image results in some pretty snazzy effects. Play with it and you'll see what I mean - you get some pretty funky colors as you move the slider back and forth. The term "hue" represents a color's location on the color wheel. As you adjust the hue slider, you are essentially "rotating" the color wheel. Although you make mess with an image's hue and fool people into thinking that they're high, the hue tool is very useful for fixing skintones. If you're working with a self-portrait, you'll be happy to know that you're able to do something if your skin comes out looking green.
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