Adobe After Effects CS4 - Manual (Page 138)

132 USING AFTER EFFECTS CS4
Importing and managing footage items
Last updated 12/21/2009
Correcting lens distortion and noise in Camera Raw
Compensate for chromatic aberration in Camera Raw
Chromatic aberration is a common defect caused by the failure of the lens to focus different frequencies (colors) to the
same spot. In one type of chromatic aberration, the image from each color of light is in focus, but each image is a
slightly different size. This type of aberration is seen as a complementary color fringing in areas away from the center
of the image. For example, a red fringe may appear 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.
Original image (top), and after fixing chromatic aberration (bottom)
Another type of chromatic artifact affects the edges of specular highlights, such as those found when light is reflected
off of the surface of rippled water or edges of polished metal. This situation usually results in a purple fringe around
each specular highlight. Similar-colored fringing can occur along edges between dark objects and very bright objects.
1 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. Look for the color fringing.
2 In the Lens Corrections tab, adjust any of these controls:
Fix Red/Cyan Fringe Adjusts the size of the red channel relative to the green channel. This compensates for red/cyan
color fringing.
Fix Blue/Yellow Fringe Adjusts the size of the blue channel relative to the green channel. This compensates for
blue/yellow color fringing.
Defringe Desaturates colored fringing around specular highlights. Choose All Edges to correct color fringing for all
edges, including any sharp change in color values. If choosing All Edges results in thin gray lines near edges or other
unwanted effects, choose Highlight Edges to correct color fringing only in edges of highlighting, where fringing is most
likely to occur. Choose Off to turn off defringing.
Look at the preview image as you move each slider left or right. If you’re adjusting red/cyan color fringing, hold down
Alt (Windows) or Option (Mac
OS) to hide the blue/yellow color fringing. Similarly, hold down Alt (Windows) or
Option (Mac OS) while adjusting the blue/yellow color fringing to hide the red/cyan color fringing. The goal is to
reduce the color fringing as much as possible.
Compensate for lens vignetting in Camera Raw
Vignetting is a lens defect that causes the edges, especially the corners, of an image to be darker than the center. Use
controls in the Lens Vignetting section of the Lens Correction tab to compensate for vignetting.
1 Increase Amount to lighten the corners, or decrease Amount to darken them.