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Tutorials-Articles: How to remove purple-cyan fringing in The Gimp

10/04/2011

How to remove purple-cyan fringing in The Gimp

(Check out the 2nd part of this tutorial here)

So, you’ve been struck by purple fringing… What’s this ?

When you take a shot with a CCD camera, zones with high-contrast (for example, the leaves of a tree with the sky as the background) may appear with a purple and green halo.

There are 3 ways to avoid this:

Oddly enough, my D7000 corrects the aberration on JPEGs, but does not apply this correction to NEFs (Nikon’s RAW file format). Since NEFs are supposed to be out-of-the-sensor images, with no corrections applied, this makes sense.

The NEF file converted by UFRawThe JPG file from the D7000

So, you have an image with CA (Chromatic Aberration) and you want to correct this with The Gimp. Quite easy:

The results:

The NEF file converted by UFRaw
The same as above
The file processed with The Gimp

In this particular example I’ve removed Magenta, Cyan and Green fringing.

This technique does not work 100% in all the cases, but it has really helped me a lot in some situations.

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