Chromatic aberration (CA) or “color fringing” is a color shift or distortion usually along high contrast edges in a photo. The wider the lens, the more likely it is that you’ll find color fringing in the picture. Old or inadequate lenses can also contribute to color aberration, so does shooting at a wide aperture.
Adobe Lightroom has several tools to remove chromatic aberration. The easiest to use is the “Remove Chromatic Aberrations” checkbox in the Lens Corrections panel. However, I found that it often doesn’t do a good enough job, especially when using wide angle lenses and/or wider apertures.
You can further tweak your photo using the “Defringing” tool on the “Manual” tab of the Lens Corrections panel (for Lightroom Classic / LrC). You’ll find a color picker and sliders for adjustments. This effectively removes most or all color fringing in the photo. BUT the defringing tool often produces very nasty color shifts in places other than where the color fringing occurred. Check for areas with metallic objects and blue sky in the background. This tool works globally, that is on the entire photo. It would be great to limit the effect exactly where needed.
Lightroom has several masking tools, including graduated and radial filters, as well as the brush tool. For chromatic aberration removal I prefer using a brush for more precise application of the Defringe or Moire tool.
Using a Brush to Defringe or remove Moire
Let’s get right to it. Open your photo containing chromatic aberrations in Lightroom and select the Masking tool. Select the brush and make sure that Auto Mask is disabled! This is very important as the Moire tool won’t work well or at all if you have the Auto Mask enabled.
Zoom in at 100% and move around using the navigator panel on the top left of Lightroom.
Select either Defringe or Moire to remove the color fringing. I’m using the Moire tool as it solves several issues at once with my main camera (the D850 can show some moire, although rarely). I suggest that you experiment with both the Defringe and the Moire tool to see what works best for you!
If you selected the Moire tool, select a value of +25 to start with. In my case (for the D850) that was enough, but you may need to make adjustments. Paint over the areas showing color fringing. It doesn’t have to be precise, but I wouldn’t want to generally apply that to the entire photo. At the same time you can remove moire that may have been introduced to the photo.
Try the Defringe tool for comparison. Which works better for you? I believe that either tool should give satisfactory results. Definitely better than the global Chromatic Aberration removal and/or Defringe tools.
Why Does the Moire Tool Remove CA?
Although a guess, I somehow figured that the Moire tool would be good to remove CA (short for Chromatic Aberration). Why is that so?
We need to look at what moire is. Moire can occur when repetitive patterns in a photograph exceed the camera’s resolution. A good explanation can be found in “What is Moiré and How it Can Ruin Your Photos“. Since almost all cameras require the Bayer filter to be applied to produce a color image, this filter in combination with repetitive patterns at around the sensor resolution can introduce strange patterns as well as color shifts. The Moire tool in Lightroom essentially removes the patterns AND the color shifts.
Most cameras use a low-pass or "blur" filter to blur the image and thus remove or minimize moire. My Nikon D850 doesn't have a "blur" filter, thus increasing pixel level sharpness. The downside is the higher potential for moire. In reality moire doesn't present itself often. The Moire tool in Lightroom definitely fixes the issue.
So the Moire tool doesn’t only tackle the moire issue, but also takes care of color shifts. In fact, it does a great job at that, as far as I can see. Please post a comment with your findings.
The takeaway for me is that chromatic aberration should be removed using a mask, not globally. You still want to tick the “Remove Chromatic Aberrations” checkbox. But any additional removal should be done with the brush tool.
Hope this helps. Leave a comment on what you think.