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2009-03-31T16:21:15Z

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2009-03-31T16:14:45Z

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'''tca_correct''' is a command-line tool shipped with [[hugin]] that can be used to automatically calculate lens [[TCA|chromatic aberration]] correction parameters. Ideal sample photos would have a lot of contrast over the entire image area, little saturated colour and no blown highlights.

== Using with fulla ==

[[fulla]] is a command-line tool for correcting [[lens distortion]], [[vignetting]] and [[TCA]] (chromatic aberration). It is capable of applying the full panotools polynomial to the red and blue channels.

First calculate some TCA correction parameters for a sample image, notice that I'm only going to bother optimising ''b'' and ''v'' parameters in the [[lens correction model]], you might get better results with the full ''abcv'' set of parameters:

tca_correct -o bv DSC_3194.ppm

This outputs some fulla parameters like so:

-r 0.0000000:0.0001197:0.0000000:0.9997630 -b 0.0000000:-0.0001142:0.0000000:1.0001841

You can now use these with fulla when converting photos from this lens:

fulla -r 0.0:0.0001197:0.0:0.9997630 -b 0.0:-0.0001142:0.0:1.0001841 -o corrected.tif DSC_3194.ppm

== Using with dcraw ==

[[dcraw]] is a command-line [[RAW]] converter with the ability to apply scaling of red/blue channels at the Bayer interpolation stage. Simple scaling is not as sophisticated as the panotools polynomial used in [[fulla]] but is good enough for nearly all purposes. Start by extracting a test image from a RAW file:

dcraw DSC_3194.NEF

Then run '''tca_correct''' on this PPM image, but tell it to only optimise ''v'' [[field of view]] for the red and blue channels:

tca_correct -o v DSC_3194.ppm

After while some [[fulla]] correction parameters will be outputted:

-r 0.0000000:0.0000000:0.0000000:1.0005943 -b 0.0000000:0.0000000:0.0000000:1.0008306

The two useful numbers (1.0005943 and 1.0008306) are the inverse of the numbers required by dcraw, so get a calculator and calculate the reciprocal of each:

1 / 1.0005943 = 0.999406
1 / 1.0008306 = 0.999170

Now when converting RAW files from this lens you can use the dcraw -C parameter to correct [[TCA]]:

dcraw -C 0.999406 0.999170 [OPTIONS...] DSC_3194.NEF

[[Category:Software:Platform:Windows]]
[[Category:Software:Platform:Linux]]
[[Category:Software:Platform:Mac OS X]]
[[Category:Software:Hugin]]

@@ Line 3: / Line 3: @@
 == Using with fulla ==
-[[fulla]] is a command-line tool for correcting [[lens distortion]], [[vignetting]] and [[TCA]] (chromatic aberration). It is capable of applying the full panotools polynomial to the red and blue channels.
+[[fulla]] is a command-line tool for correcting [[lens distortion]], [[vignetting]] and [[TCA]] (chromatic aberration). It is capable of applying the full panotools polynomial to the red and blue channels, thereby correcting any transverse chromatic aberration.
 First calculate some TCA correction parameters for a sample image, notice that I'm only going to bother optimising ''b'' and ''v'' parameters in the [[lens correction model]], you might get better results with the full ''abcv'' set of parameters:
@@ Line 27: / Line 27: @@
    tca_correct -o v DSC_3194.ppm
-After while some [[fulla]] correction parameters will be outputted:
+After a while some [[fulla]] correction parameters will be outputted:
    -r 0.0000000:0.0000000:0.0000000:1.0005943 -b 0.0000000:0.0000000:0.0000000:1.0008306

Tca correct - Revision history

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