Chromatic Aberration, what the heck is it?
Well a quick google search will give you the result below and tell you about "wavelengths of electromagnetic radiation". Right... But the second half of that definition is a little closer to the answer we're looking for - "it causes colored fringes in the image..."
And the colored fringes are what I attempted to demonstrate in a recent video tutorial but I thought that a still image demonstration might work better. For the record there are better resources out there for describing the technical aspects to chromatic aberration and exactly what it is and exactly what causes it. But we know we don't like it and we know we want to get rid of it.
In the upper left image above you can see that on the right edge of the trees is a slight green cast and on the left edge is a slight red cast. That is chromatic aberration. Depending on your lens, camera and the lighting you're under it could be more or less noticeable than in this image. It does tend to be more prevalent when using lower quality lenses. But no matter the cause we need to get rid of it! And luckily Lightroom makes it very easy. In the right panel of the Develop Module you will see a panel labeled 'Lens Corrections' and there you will find the "Remove Chromatic Aberration" checkbox. Upon checking that box you will (likely and hopefully) see that fringing disappear. In the upper right image above you can see the zoomed area of the image after that button has been checked and see that the color fringing is gone. So that is how you can quickly and easily get rid of chromatic aberration.
So removing chromatic aberration will get rid of green and magenta color fringing but there can also be purple color fringing in an image as well. Many times it is less noticeable but nonetheless it should be remedied. And Lightroom makes that fairly easy as well. In the image above I found some purple color fringing in the tree line. To fix this issue I stayed in the "Lens Correction" panel but moved from 'Profile' to 'Manual'. I then simply clicked to "grab" the eyedropper tool and then hovered over the purple fringing area (as seen in the upper left of the image above) and clicked with that eyedropper. Lightroom then sampled where I clicked and corrected to remove the purple color fringing (as seen in the lower left of the image above). You can see that there are options for changing the "amount" and the "hue" and I suggest simply leaving them at there default settings - Lightroom does a pretty good job!
So there you have it! That's how to go about fixing color fringing in your images. And I do suggest doing these steps first as further developing and color adjustments can make fixing color fringing more challenging later in the develop process.