In previous lessons we have learned how to make corrections using some, of the many, tools on the toolbar. Not all images require such major surgery. A picture may need to be lightened just a bit or one of its colors may need slight adjustment. You don't have to understand ALL the gory details about how color works to use it for corrections or eye-catching effects. It's possible to use trial and error to achieve acceptable results. However, just as you don't need to be an electrician to know you don't stick a fork in the toaster, it's good to know a little bit about the basics before you go poking around.
Artificial color systems such as computers, scanners, monitors, and other peripherals attempt to model the colors that the human eye perceives. The colors within the definition of each model are referred to as its color space. Of the three most common models, the one based on the hue/saturation/lightness (HSL) of colors is the most natural and the easiest for the human eye to perceive since it has a continuous range of colors that vary in brightness or richness.
You can use this type of model when you adjust colors with the Hue/Saturation dialog boxes. The color rings represent the colors in the image, where the outer ring represents the original values and the inner ring represents the adjusted values. By selecting an option from the Edit drop-down list, you can edit the master color, or you can choose a specific color range to adjust.