Compensating for chromatic aberration

Chromatic Aberration is a common lens defect in which the lens focuses different frequencies (colors) of light differently. One type of chromatic aberration results in the different colors being in focus, but each color's image is a slightly different size. This type of aberration results in complementary color fringing in areas away from the center of the image. For example, the fringing can appear as a red fringe on the side of an object toward the center of the image, and cyan fringe on the side of the object away from the center of the image. The controls in the Lens tab address this problem.

To compensate for chromatic aberration:

1. Make sure the Camera Raw dialog box is in Advanced mode.
2. Zoom into an area near the corner of the preview image. For the best results, the area should contain very dark or black detail against a very light or white background. The color fringing should be visible.
3. In the Lens tab, move one or more of the following sliders:
Chromatic Aberration R/C
Adjusts the size of the red channel relative to the green channel. This compensates for red/cyan color fringing.
Chromatic Aberration B/Y
Adjusts the size of the blue channel relative to the green channel. This compensates for blue/yellow color fringing.
Watch the preview image as you move the slider to the left or right. If you're adjusting red/cyan color fringing, you can hold down the Alt (Windows) or Option (Mac OS) key to hide the blue/yellow color fringing. Similarly, holding down the Alt (Windows) or Option (Mac OS) key while adjusting the blue/yellow color fringing will hide the red/cyan color fringing. Your goal is to reduce the color fringing as much as possible.