White halo after chromatic aberration removal

joshnl

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Hi all,

I've been having a problem related to chromatic aberration lately with my photo processing. The latest versions of ACR are great for removing the colour fringing associated with CA. However, I've noticed a problem with backlit scenes. Let's say you have a dark rock with a relatively bright (but still darkish) sky behind it, and there is colour fringing around the rock. Once the actual colour component of the fringing has been removed, a white ring/halo remains around the rock (i.e. the luminosity component of the fringing still remains).

Does anyone know how to remove this? I imagine it would involve lowering the luminosity of the fringe, but I can't figure out a way to achieve this. Would really appreciate any suggestions. Thanks!

Josh
 

TCampbell

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You can imagine CA as separating the light into color channels where each channel's image size is slightly different than the next. The red image would be the largest (long waves bend the least) and the blue image would be the smallest (blue -- actually violet but normally we don't think of a "violet" color channel -- is the shortest wavelength so it bends the most.)

Usually a CA tool simply resizes the channels.

If you want, post the image and we'll take a look. You've flagged your profile with "My Photos are NOT OK to Edit", so we wont adjust/edit them. If you'd like us to take a crack at adjusting them with our tools (I use Aperture for this), let us know specifically that you're asking for this, because we normally would never do this based on your profile preference.
 
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joshnl

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You can imagine CA as separating the light into color channels where each channel's image size is slightly different than the next. The red image would be the largest (long waves bend the least) and the blue image would be the smallest (blue -- actually violet but normally we don't think of a "violet" color channel -- is the shortest wavelength so it bends the most.)

Usually a CA tool simply resizes the channels.

If you want, post the image and we'll take a look. You've flagged your profile with "My Photos are NOT OK to Edit", so we wont adjust/edit them. If you'd like us to take a crack at adjusting them with our tools (I use Aperture for this), let us know specifically that you're asking for this, because we normally would never do this based on your profile preference.

Thanks very much, Tim, for your response and your offer to give me a hand with this.

When I made that indication in my profile, I suppose I didn't understand why it was asking if my pictures could be edited by other members (I'm brand new to this forum), so I erred on the side of caution. I'm happy to have you fiddle with this particular picture - if you don't mind - to see if you can help me out with this issue.

Do I simply upload the picture in this thread, or do I send it directly to you?
 

TCampbell

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joshnl

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You can either upload it to the forum (here) (there's a post on how to do this here: http://www.thephotoforum.com/forum/...forum-functions-pictoral-guide-using-tpf.html ) or you can upload it to any website and provide a link.

No need to send it directly to me. There are MANY members who are quite skilled at editing. You may be surprised at the results.

Thanks again, Tim.

I'm uploading the picture here. I've gone to town on processing it already (it's a composite of two exposures, one for the sky, one for everything else), but the halo effect I mentioned is still there, and quite obvious, at least to my eye.

Any suggestions you or anyone else could provide would be much appreciated.

EDIT: I should mention that, although it is a composite of two images, the halo effect is not due to the blending of the images. It was present in the original 'sky' RAW file as well.

$_MG_3934-Edit (1920out)-FB.jpg
 

Gavjenks

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I have no idea how to address your problem. But awesome shot there.
 
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joshnl

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Can people at least let me know if they've had similar problems? I wonder if this is a common issue, and people just deal with it; or if maybe my lens (the Canon 10-22mm f3.5-4.5) is a particularly bad performer when it comes to chromatic aberration.

Thanks.
 

Buckster

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I recorded a video to show one possible way in Photoshop CS6 to deal with it. As with most things Photoshop, there are no doubt dozens of ways to deal with this situation. Anyway, here's one I use on occasion:


If you've got the bandwidth for it, I suggest viewing it at YouTube rather than here, and at 720p HD quality and full screen.
 
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joshnl

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I recorded a video to show one possible way in Photoshop CS6 to deal with it. As with most things Photoshop, there are no doubt dozens of ways to deal with this situation. Anyway, here's one I use on occasion:


If you've got the bandwidth for it, I suggest viewing it at YouTube rather than here, and at 720p HD quality and full screen.

Buckster, you're an absolute star. Extremely smart way to tackle this problem - I would've never thought of that in a million years. Thank you so, so much. REALLY appreciate it.
 
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