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Chromatic aberration in LR4.1 - not getting good results

Apr 12, 2012 9:56 AM

Tags: #chromatic #chromatic_aberration #lr4.1rc

l'm not getting good results with Canon EF 50 f1.4 lens + Canon 7D. More or less, I see no improvement in CA. LR4.1 does very little to actually remove major CA's.

In fact, I discovered that in this particular situation, it looks to me even better with CA turned off.

 

Does this vary from lens to lens? Can this be further tweaked and fully removed by software? I currently use brushes in PS to manually paint and remove CA's.

 

Here's a 100% crop. Notice the white arrow that I made. CA OFF looks better.

http://ivframes.com/ca-ex.jpg

 
Replies
  • Currently Being Moderated
    Apr 12, 2012 10:00 AM   in reply to ivframes

    The new one-click CA adjustment has pleased a lot of people.  But there are some who have found its limitations.  Someone who knows more than I about the development cycle in Lightroom has suggested that there "could" be some additional adjustments provided in the near future.  For now, I suppose the best advice is just to be patient.

     
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    Apr 12, 2012 10:03 AM   in reply to JimHess

    Still, this particular example screams axial CA.

     
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    Apr 12, 2012 11:01 AM   in reply to ivframes

    I have the same problem with this lens and have not been able to reduce. Not only do I get purple magenta fringing in the highlights I get a sickening green in the shadows, especially when shooting metalic objects. The auto correction does not make a visible difference

     

    I can reduce this by shooting at a smaller aperature, but sort of defeats the look I am trying to get.

     

    More than pleased to share a sample

     

    MK

     
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  • Currently Being Moderated
    Apr 12, 2012 12:51 PM   in reply to MikeKPhoto

    There are two types of CA.

     

    Transverse (Lateral) CA : Color shifts perpendicular to the optical axis, in the plane of the sensor or film.

    Increases with distance from image center.

    Use LR's Chromatic Aberration tool(s).

     

    Axial (Longitudinal) CA: Color shifts in the direction of the optical axis

    Uniform across image, but most noticeable in bright highlight areas.

    Use LR's Defringe tool.

     

    What you are describing is axial CA. LR's CA tool is designed to correct lateral aberrations. Axial chromatic aberration (purple fringing) is usually uniform in size across the image, but most noticeable along dark edges in bright highlight areas (or vice-versa). You may be able to correct axial CA in a specific area of an image using LR3's manual CA tools, but then it will introduce longitudinal CA in other areas of the image. There was recent post where it was shown that LR3's manual CA controls do a better job than LR4's 'automatic' CA correction for images with pronounced lateral CA:

     

    http://forums.adobe.com/message/4311373#4311373

     

    Axial CA behaves in a non-linear manner compared to Lateral CA, so it's difficult to design a tool for completely correcting it. Images on different sides of the focal plane (i.e. out of focus areas) take on different colored CA as you described, and as demonstrated in the picture at this link under heading 'Longitudinal/Axial Chromatic Aberration:'

     

    http://mansurovs.com/what-is-chromatic-aberration

     

    Currently the only tool in LR that may help partially correct Axial CA is the 'Defringe' tool under Lens Corrections Manual tab. It's also a good idea to view your final results in LR at a view magnification that is closer to the final image print or onscreen view size. On my 25" 1920 x 1080 monitor the 1:1 (100%) view size is equivalent to a 42" x 64" print size with 5D MKII 21Mp images (~89 pixels/inch). You will probably find the axial CA much less objectionable at your final output size.

     
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    Apr 12, 2012 1:44 PM   in reply to MikeKPhoto

    MikeMikePhoto wrote:

     

    I can reduce this by shooting at a smaller aperature, but sort of defeats the look I am trying to get.

     

    If you can reduce/eliminate the CA by stopping down, then that CA is longitudinal CA. The amount and severity of this type of CA is impacted by F stop. Laterial CA is not changed by stopping down. What the current CA tool is designed to do is address laterial CA. Hopefully Adobe is working on addressing longitudinal CA as well. But it's a different (and more difficult) solution.

     
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    Apr 12, 2012 4:47 PM   in reply to ivframes

    Try using the moire brush ...

     
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