CA occurs when the different color wavelengths of light (red, green, and blue) are focused onto slightly different spots on your camera’s sensor. This causes slight overlap on hard edges of objects in a shot, which is seen as color fringing. CA is a product of a lenses’ optical design. Higher quality, more complex lenses tend to produce little to no CA, while simpler, less complicated lenses suffer from it more.
If you are looking to remove some CA in Photoshop there are many ways that you can go about it, ranging from easy built-in sliders to more advanced processes utilizing custom layers and brushes. Photographer Jimmy McIntyre recently posted on YouTube an overview presenting five ways to correct chromatic aberration using Photoshop.
In addition to the easy sliders that come with Photoshop’s Camera RAW plug-in, one method that McIntyre mentions is the Gaussian blur method. This involves creating a duplicate layer of your image, applying a Gaussian Blur until the color fringing is gone, and then using a mask to paint in the effect where needed. It’s a bit more work than the easy sliders, but in situations like the one demonstrated in the video where the easy sliders don’t cut it, it can be a life saver.
Another more advanced method that McIntyre explains is the clone stamp method, which can take a lot of time. But in those situations where nothing else is working, and you want your image to look its absolute best, it can be worth it. Creating art is not easy, and these are some of the little things that one can do as a photographer to really improve an image.