Chromatic aberration removal in software, camera, etc

On 2014-03-10 04:33:54 +0000, RichA said:

I'm wondering how it works, exactly. Does it just remove chromatic fringes
from light-dark edges, or does it really remove it completely? Reason is,
we don't see chromatic aberration with our eyes except on light-dark edges
, but CA is actually suffused across the entire image, resulting in lowered
contrast. So, I was wondering if the software actually removed the defocu
sed blue and red across the image, or just on the edges?

Both LR5 and ACR do a pretty good job of correcting CA.

Here is an example, before and after showing some purple fringing,
corrected in LR5.
https://dl.dropbox.com/u/1295663/Fil...enshot_612.jpg

Do not mistake chroma noise for CA, that is also correctable provided
you correct luminance noise first.

Then color casts are something else altogether, and are also fixable.
--
Regards,

Savageduck

On 10/03/2014 05:01, Savageduck wrote:
On 2014-03-10 04:33:54 +0000, RichA said:

I'm wondering how it works, exactly. Does it just remove chromatic
fringes
from light-dark edges, or does it really remove it completely?
Reason is,
we don't see chromatic aberration with our eyes except on light-dark
edges
, but CA is actually suffused across the entire image, resulting in
lowered
contrast. So, I was wondering if the software actually removed the
defocu
sed blue and red across the image, or just on the edges?

It is doing neither.

The chromatic aberration compensation is to separate the image into red,
green and blue and then correct the slightly different effective
magnifications of the red and blue images using the green as a
reference. It is a correction of lateral chromatic aberration which gets
worse the closer to the edge of field that you go.

This is different from the hardline diffraction limited optics case in
astronomical telescopes where the red and blue images are noticeably out
of focus relative to the green image. Residual transverse chromatic
aberration being the hardest thing to remove. See:

http://en.wikipedia.org/wiki/Chromatic_aberration

Both LR5 and ACR do a pretty good job of correcting CA.

Here is an example, before and after showing some purple fringing,
corrected in LR5.
https://dl.dropbox.com/u/1295663/Fil...enshot_612.jpg

Do not mistake chroma noise for CA, that is also correctable provided
you correct luminance noise first.

Then color casts are something else altogether, and are also fixable.



--
Regards,
Martin Brown