Choosing Automatic Color Correctors in Photoshop

Photoshop has three automatic correction tools that can, in many cases, provide an improved appearance with a simple click of a menu command. However, none of the automatic controls is likely to do as good a job as you can do manually, and sometimes automatic controls even do more harm than good. If you have an average image (one that doesn’t require a great deal of correction), you can try them out to see if they help. If not, you’ll want to apply the manual tools explained later in this chapter to produce the exact look you want. Here’s an introduction to the three tools:
- Auto Levels: Adjusts the highlights (brightest portions of an image that contain detail) and shadows (the darkest portions of an image that contain detail).
- Auto Color: Adjusts the color balance of an image.
- Auto Contrast: Controls the relationship between the balance of bright and dark tones. You don’t need to know much about levels, color balance, or contrast to use the automatic correctors (that’s why they’re automatic), but you find out more about each of them later in this chapter when I show you how to take over the controls and make adjustments manually.

Auto Levels
The Auto Levels command uses a bit of built-in Photoshop intelligence to automatically apply the Levels command (discussed later in the chapter) to your image. Auto Levels works best with average images that could use a bit of tweaking but have lots of detail in the highlights, shadows, and mid-tones. Auto Levels defines the very lightest and darkest pixels of each of the three colors as white and black, respectively, and then arranges the mid-tone pixels in between. Along the way, as it balances the tones in your image, the command may reduce color casts or even introduce some. You can fine-tune the color manually after Auto Levels has done its work, using the tools described later.

To try out the Auto Levels command, just choose Image-->Adjustments-->Auto Levels, or press Shift+Ctrl+L (Shift+Ô+L on the Mac). Although Auto Levels can improve your contrast, it may also produce an unwanted color cast. If this happens, cancel the command and try the Auto Contrast command. If that still doesn’t improve it, try the Levels command instead.

Auto Color
The Auto Color command adjusts both the color and contrast of an image, based on the shadows, midtones, and highlights it finds in the image. You usually use the command to remove a color cast (or bias) or balance the color in your image. Sometimes using Auto Color can be helpful in correcting oversaturated or undersaturated colors as well. You can access the command by choosing Image-->Adjustments-->Auto Color, or by pressing Shift+Ctrl+B (Shift+Ô+B on the Mac).


Auto Contrast
Like its manually operated cousin, the Brightness/Contrast command, the Auto Contrast command fiddles with the overall contrast and colors (if you’re working with a color image) in an image, rather than making adjustments to each color individually. Auto Contrast converts the lightest and darkest pixels to white and black, respectively, making all highlights in the image lighter and all shadows darker without changing the color values. This command may not do as good a job at improving contrast, but it retains the color balance of an image and doesn’t cause any nasty color casts. Try using this command on hazy images. To use Auto Contrast, choose Image-->Adjustments-->Auto Contrast, or press Alt+Shift+Ctrl+L (Option+Shift+Ô+L on the Mac).