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Double CA correction?
  
 
Parariss
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p.3 #1 · p.3 #1 · Double CA correction?


Poking around on the Adobe website, it looks like the suggested workflow is as described in this thread: if (and only if) the standard lens profile (assuming one exists) is considered inadequate, you can check the CA box.

From there, it looks like the intent of that checkbox is for LaCA to be corrected fully automatically by Lightroom. Then, the user manages LoCA correction using the manual sliders (Develop Module > Lens Corrections section > Manual tab), optionally using the eyedropper tool to pick out the exact shades of undesirable purple and green.

So, if you don't like the way Lightroom handles LoCA, you can either adjust it or effectively turn off LoCA correction entirely by turning down the purple/green Amount sliders on the Manual tab to zero. So, in a way, you can in fact separate LaCA correction from LoCA correction.

Hope this makes sense and helps.



Sep 25, 2017 at 12:52 AM
DavidBM
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p.3 #2 · p.3 #2 · Double CA correction?


Parariss wrote:
Poking around on the Adobe website, it looks like the suggested workflow is as described in this thread: if (and only if) the standard lens profile (assuming one exists) is considered inadequate, you can check the CA box.

From there, it looks like the intent of that checkbox is for LaCA to be corrected fully automatically by Lightroom. Then, the user manages LoCA correction using the manual sliders (Develop Module > Lens Corrections section > Manual tab).

So, if you don't like the way Lightroom handles LoCA, you can either adjust it or effectively turn off LoCA correction entirely by turning
...Show more

Maybe that's what they say, and maybe that's partly right for native lenses, but unfortunately that's not what seems to happen for non-Native lenses.

If you use the checkbox to correct LaCA it also makes an automatic attempt at LoCA and other axial colour fringing. This produces some side effects. But the purple/green sliders ARE at zero by default, even when the box is ticked and some automatic LoCA correction is happening. So the auto LoCA can't be turned off or reduced while LaCA correction is handled, on non-native lenses.

Of course you can untick the box, and do your own LoCA corrections with the sliders. But then (in non-native lenses) LaCA is not corrected.



Sep 25, 2017 at 12:59 AM
Fred Miranda
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p.3 #3 · p.3 #3 · Double CA correction?


DavidBM wrote:
Maybe that's what they say, and maybe that's partly right for native lenses, but unfortunately that's not what seems to happen for non-Native lenses.

If you use the checkbox to correct LaCA it also makes an automatic attempt at LoCA and other axial colour fringing. This produces some side effects. But the purple/green sliders ARE at zero by default, even when the box is ticked and some automatic LoCA correction is happening. So the auto LoCA can't be turned off or reduced while LaCA correction is handled, on non-native lenses.

Of course you can untick the box, and do your own LoCA
...Show more

Adobe should have an auto-fix for LoCA as well. (and leave the LaCA correction alone)
Of course it would not be perfect but it would not be too hard to develop an algorithm that scans an image for the correct 'magenta/green' tone around OOF high contrast areas and reduce it.



Sep 29, 2017 at 04:34 PM
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