> Hi
> My digicam generally delivers great pics, BUT like many other cameras it
> suffers from blue/purple bleed in high contrast areas especially next to
> highlight. I know, you can buy plugins for PS, but has anybody written a
> macro, he or she will share?
> I'm interested to know how it works, if possible.
Color fringing is caused by an optical defect in the lens design that causes different colors to be refracted differently. The result is that the red, green, and/or blue images are different in size, with red being largest and blue being smallest. Fringing typically shows up in the upper corners of an outdoor image, where the horizon or foliage is silhouetted against the sky.
The quick fix is to use the sponge in desaturate mode to get rid of the unwanted colors, but this is a crude solution at best. A more accurate improvement is can be done by resizing the red and/or blue channels slightly to match the green channel, which is used as a reference.
Here's a procedure for versions of Photoshop that do not have the Distort>Lens Correction filter. Use the magnifying glass to zoom in on the most extreme area of fringing. Click on the channels, palette, highlight the red channel, click on the "eyecon" for RGB to view the color image, Select All, and select the Edit>Transform tool to minimize the fringing. Repeat for the blue channel.
Magenta/green fringing is fixed by resizing the red channel. To remove any magenta fringe is on the outside of the object, (or green fringe is from the inside) make the red channel smaller. When you are done resizing red you should have either no fringe, or a blue/yellow fringe. If you have a blue yellow fringe, make the blue channel larger as necessary. Use the numeric text fields to enter the zoom setting, since you'll be working down to the tenths of a percent.
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Mike Russell
www.curvemeister.com/forum/