Removing fringing (or is it CA? What's the difference again?)

Three sample shots (first shot with canon 85/1.8@1.8, second two with siggy 50/1.4@1.4)

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Are you shooting RAW or jpeg?

Raw. Those files are at home and I am not though.

Yeah, it's lateral chromatic aberration. (also known as transverse chromatic aberration)

It's common when you shoot high contrast wide open. Stop down a bit and it will get better.

John the Geek wrote in post #10959150
Yeah, it's lateral chromatic aberration. (also known as transverse chromatic aberration)

It's common when you shoot high contrast wide open. Stop down a bit and it will get better.

No actually most of what he is showing is purple fringing and longitudinal aberrations (The fortune ticket shows both lateral and longitudinal and a little bit on the watch as well). OP, things in front of your focus point that are OOF will have purple fringes on high contrast edges and behind the point of focus will be green. Only way to get rid of these is to desaturate them. Or you can just accept that they occur and stop viewing your images at 100%

It's not just a 100% viewing problem in every case though. And I know they occur, but I've heard people say that fringing is not so terrible to fix so I'm wondering exactly what this not so terrible process is. I could see selective desaturation being a fix but it could get cumbersome and in cases like the camera manual where it's not so easy to select for the fringing and not for the color around it.

FatCat0 wrote in post #10962813
It's not just a 100% viewing problem in every case though. And I know they occur, but I've heard people say that fringing is not so terrible to fix so I'm wondering exactly what this not so terrible process is. I could see selective desaturation being a fix but it could get cumbersome and in cases like the camera manual where it's not so easy to select for the fringing and not for the color around it.

Lateral CA's are easy to fix in RAW software. Its literally just checking a box or moving a slider.

Longitudinal CA's and purple fringing are not as easy to fix and will require a number of methods most involving desaturating the colors involved.

This short description may be helpful:

http://www.dxo.com …ry_corrections/​aberration

For me, it's irrelavent whether is lateral or longitudinal, purple, red, or cyan. It's all junk and needs be ignored or removed. And if removed, with the simplest and quickest method possible.

Removal tools fall into 3 categories:

1. Raw converters, like ACR, provide some CA sliders. My experience is only with ACR, and I think it does a poor job. When it removes the CA in one area it often adds CA in another area. Getting it all out often requires multiple conversions and tedious masking. Maybe other converters like Dx0 do a better job.

2. Third party noise reduction software. Noiseware, Noise Ninja, etc. While these do a good job at removing normal noise, I find they do a poor job removing CA. Farily worthless, in fact.

3. Photoshop PP, which has a few methods.

3A. Targeting the CA "color" and desaturating. Most often this turns a color fringe into a white or gray fringe. Still a fringe. And it requires tedious masking because the desat will impact other areas of the image.

3B. Targeting the CA and using Match Color or Replace Color. Works a little better than desat, but requires very precise masking and multiple steps for multiple colors.

3C. Going to LAB mode and bluring the A channel, or B channel, or both. Usually only the A channel needs blurred. Works amazingly well, but often leaves a little halo. Also requires some masking to protect other areas, but easy and quick masking. Just black mask it and paint over the CA with white.

3D. Finally, the old Photoshop noise reduction tool. I mention this one last, because I think it works best. Filter/Noise/Reduce Noise. Set the Strength and Sharpen Details to 0 and just work the Reduce Color Noise slider. It also creates a halo sometimes. But that halo is far less bothersome than the fringe. The halo can be removed with masking, but that takes some fine control.

The noise reduction tool works pretty well, though it eats some detail. At the very least it makes it easy to make a masking layer for problem spots thanks!

DXO does a nice job at addressing all of these issues during conversion of the RAW data, provided you shoot with a supported camera-lens combination.

Kirk

Here is a DXO example - this is an image that was shot RAW with a Powershot s90. All I did was uncheck the CA corrections box to let the CA artifact appear. To get rid of it, check the CA box, with defaults. DXO has a s90 corrections module, so it is all automatic based on DXO's characterization of the s90 CA artifacting.

The crunchiness in the image is from the default "Lens Softness" correction that is too strong for this image, at 400% zoom.

Kirk

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And, now that Lightroom has the s90 lens correction profile, Lightroom handles this CA for this image from the s90 as well. although, there appears to be some slight residual fringe compared to the DXO correction.

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And, of course, CA handling in DPP.

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kirkt wrote in post #10987332
And, of course, CA handling in DPP.

Maybe it's because it's zoomed out a bit more than the others, but the DPP image looks infinitely better all around.

=)