Chromatic Aberration????

[JulieM]

I took this image yesterday at the Canadian War Museum. The subject sculpture was backlit through the window by bright sunshine and beautifully spotlighted from the front. Obviously, I wasn't up to the task of handling this exposure challenge and I will try to go back on a day when the backlighting will not be such an issue. But, while I was pondering whether the image could be saved, I noticed the strong purple and green fringing in the highlights. I figured it would be a good chance to play with the chromatic aberration sliders in LR but they didn't seem to solve the problem.

Question 1 - is this chromatic aberration or not?
Question 2 - Has anyone used this tool successfully and if so can you offer me any tips?
Question 3 - Would there be another non-LR method of dealing with this?

Any help with achieving a good exposure would be welcome too! Many thanks!

[Michel B]

For me, it's not chromatic aberration, which is linked to the lens geometry (especially wide angles). This is a phonomenon, whatever its name, which is linked to the behaviour of the sensor when there is a very high contrast, typically light sky showing through branches.
The built-in tools are good for chromatic aberration, not for this.
There are different ways to correct this. They are based on selecting the purple fringe tint and desaturating it. I'm sure there are tutorials on this subject.

[JulieM]

Merci, Michel! This was taken with a 50mm f/1.4 lens and I've not noticed it before, but perhaps I've avoided the strongly contrasted subjects before.

[Michel B]

I am pretty sure your 50mm lens is not subject to chromatic aberration, like many zooms or wide angles. The reason is the very high contrast. There are actions to correct it, but with some patience you can get the best results by painting on blank layer on color mode, after having sampled nearby colours. Of course you need to paint in a selection (magic wand) or use a mask.

[Edmund]

Julie, I took a PSE-4 course a few years ago at eclectic academy and there was a section on how to remove "Chromatic Aberations AKA "the dreaded purple fringe"".
Didital images can be the victim of CHROMATIC ABERRATIONS. They can be difined as those purple, or blue highlights that sometimes will show up around lights or areas like skylines.
Just a quick rundown but in PSE or CS one would go to ENHANCE>ADJUST COLOR> ADJUST HUE/SATURATION
CHOOSE MAGENTA (OR COLOR MATCHING THE FRINGE COLOR)
SLIDE THE SATURATION SLIDER TO THE LEFT UNTIL THE FRINGE TURNS GREY AND IS NO LONGER OBVIOUS.
I have not played around with that slider in Lightroom but according to Martin Evening in his book "The Adobe Photoshop Lightroom Book" the sensors in our latest Digital camera are so more capable of resolving to a much finer level of detail then was possible with film that as a consequence color fringing sometimes becomes more apparent. Any way I hope this helps out.
Eddie

[Chuck S.]

I don't even see the fringing in the Pixentral image you posted. Either my display or my eyes - or both - just aren't up to the task...

Where is it most pronounced?

[JulieM]

Originally Posted by Edmund

Julie, I took a PSE-4 course a few years ago at eclectic academy and there was a section on how to remove "Chromatic Aberations AKA "the dreaded purple fringe"".
Didital images can be the victim of CHROMATIC ABERRATIONS. They can be difined as those purple, or blue highlights that sometimes will show up around lights or areas like skylines.
Just a quick rundown but in PSE or CS one would go to ENHANCE>ADJUST COLOR> ADJUST HUE/SATURATION
CHOOSE MAGENTA (OR COLOR MATCHING THE FRINGE COLOR)
SLIDE THE SATURATION SLIDER TO THE LEFT UNTIL THE FRINGE TURNS GREY AND IS NO LONGER OBVIOUS.
I have not played around with that slider in Lightroom but according to Martin Evening in his book "The Adobe Photoshop Lightroom Book" the sensors in our latest Digital camera are so more capable of resolving to a much finer level of detail then was possible with film that as a consequence color fringing sometimes becomes more apparent. Any way I hope this helps out.
Eddie

Thank you, Eddie. I appreciate the suggestion. Will try that tomorrrow...

[JulieM]

Originally Posted by Chuck S.

I don't even see the fringing in the Pixentral image you posted. Either my display or my eyes - or both - just aren't up to the task...

Where is it most pronounced?

Chuck, the purple fringing is most evident on the straight edge of the sculpture on the left hand, back side (nearest the windows). In my RAW image when viewed in LR, it extends from top to bottom of that edge. I also see green fringing around the edges of the windows. I suppose that could be something different, but the windows are actually a grey metal. Maybe I should have uploaded the RAW image...

[Edmund]

Boy now I'm really confused. On my display I can see pronounced blue edge fringing on the bottoms and some sides of the windows frames. I'll look again to see if I can pick up the others.
Chuck, you can see the fringing on the botom of all the windows even without blowing up the image in pixentral.
Eddie

[Edmund]

Just a little footnote. I recently took a image of a Grumman A-6E Intruder and the cockpit, wing edges, and any other sharp edge were frindged with a sort of blue color so much so I thought it was about 10 feet out of focus. I deleted that image so can't show you a example.
Eddie