Problem : Solution Use the Levels command to correct color casts

Problem : Solution Use the Levels command to correct color casts

Problem: Unnatural color obscures the beauty of an image.

Solution: Use the Levels command.

One of the most common, and essential, tasks when editing full-color photographs is adjusting color. Time after time, you'll encounter excellent images that hide behind a veil of unnatural color, known as color cast. This shift in color may be caused by the inherent deficiencies of a scanner or digital camera or by the effect of incandescent or fluorescent lighting. In Photoshop, there are a variety of methods you can use to remove a color cast and reveal the true colors of an image. Any method we choose, however, should produce the desired result with the least amount of time and effort. The Levels command, although less powerful than the Curves command, allows us to target and eliminate color casts with fewer steps.

Identifying a simple color problem

To begin, open an image file in Photoshop that displays an unnatural color cast you'd like to eliminate. Our sample image of vegetables against a gray background has an unattractive green color cast covering the entire image. Let's assume that we already know the background should be a cool gray and not green.

These types of color casts are easy to identify because they affect the entire image and often show up as a blue, green, or red cast. If you're unsure which color might be causing an imbalance, look for an area in the image that you know should be neutral gray. Resetting the neutral gray values eliminates a color cast and reveals the true colors in your image.

Correcting a color cast with the Levels command

1.	Open the image and select the Eyedropper tool from the Toolbox.
2.	Click on a medium tone portion of the background affected by the color cast. Your Set Foreground Color swatch shows the color selection.
3.	Create an adjustment layer in your Layers palette by clicking the Create New Fill Or Adjustment Layer button and selecting Levels from its dropdown list.
4.	Double-click on the Set Gray Point eyedropper tool in the resulting Levels dialog box. The Color Picker dialog box opens and displays values for neutral RGB midtonesin this case, a value of 128 for each of red, green, and blue.
5.	Change the value for each color so they're equal and then click OK.
6.	Use your Eyedropper tool to click once in the same midtone area affected by the color cast. The green-gray background changes to neutral gray, and the color cast within the midtones in all parts of the image disappears, as shown in our Solution image.
7.	Adjust the highlights. In our example, we only needed to adjust the white point slider (to the left) to brighten the highlights, and we moved the midtone slider slightly to the left to open up mid-level shadow detail.
8.	Click OK. You may choose to finish up with some selective sharpening and spot retouching.

Remove color casts with Levels

Color correcting an image is as much art as it is science. You'll find that your success, like so many tasks in Photoshop, improves with patience, practice, and careful analysis of color. Knowing how to rescue a photo from behind an unattractive haze will give you the skills needed to produce great-looking images.

Color calibrate your monitor

Your monitor can have a color cast of its own. If that's the case, any color correcting you perform in Photoshop may be unsuccessful. Always start from the most ideal conditions available to you to produce consistent, aesthetically pleasing results.

Before you begin evaluating images onscreen, follow the monitor manufacturer's process for achieving accurate color display in your work environment. In fact, it's a good practice to re-run the color calibration scheme for your system once a month to allow for the changing physical condition of your monitor's electronics.

If you have the ability to calibrate your monitor to the output device (color copier or offset press, for example), now is the time to do that as well. Contact your print vendor for information on the best method for achieving predictable color between your system and theirs. For more on calibrating your monitor, see the Introduction.