Have you ever heard the expression ‘the devil is in the details?’ In photography, the devil is Chromatic Aberration (CA).
In this article, you will learn what Chromatic Aberrations are. Also how to minimalize it and hen how to correct it.
What is Chromatic Aberration?
Chromatic Aberration usually manifests itself in the form of purple fringing. Red, blue, cyan, and green fringes can also be present.
These color shifts appear alongside high contrast edges. This is where very light or bright areas mix with very dark areas.
For example, a shaded building in the same image as an overcast sky.
What Causes Chromatic Aberration?
Firstly, let’s look at the general idea behind light and color. This might come as a surprise to you, but white light does not exist. And white is not a color.
It’s how we perceive a combination of different colors. These are in the visible part of the electromagnetic spectrum.
Every color behaves in its own particular way when passing through a material. A prism “disperses” them, and they form a familiar rainbow.
The refractive index causes dispersion. This is the index of the material white light is passing through.
Refraction is stronger for the light of short wavelengths (blue). It’s less intense for the light of long wavelengths (red).
And finally, different kinds of glasses cause refraction or dispersion of various intensities.
The Different Types of Chromatic Aberration
There are two types of Chromatic Aberration: Longitudinal and Lateral Chromatic Aberration.
Longitudinal Chromatic Aberration
What Is Longitudinal Chromatic Aberration?
Longitudinal Chromatic Aberration (LoCA) is also known as ‘axial’ aberration.
It appears when the lens cannot focus on all the different colors on its focal plane (the sensor).
One or more colors are then focused either in front or behind the focal plane.
What Does Longitudinal Chromatic Aberration Look Like?
LoCA appears in high contrast areas and is visible either at the edges or the center of the frame.
It presents itself as green or purple fringing. It’s either in front or behind the object in focus.
The image below shows a fair amount of longitudinal chromatic aberration. You’ll find it along every contrasted edge, regardless of their position in the frame.
LoCA is easy to identify. It changes color when you focus in front of or behind the object. Luckily, it disappears when a narrow aperture is used.
Take a look at the image below, captured at f/1.4. You’ll find the purple fringing in front of the window edge.
Transverse/Lateral Chromatic Aberration
What Is Transverse Chromatic Aberration?
Transverse Chromatic Aberration, TCA, is also known as ‘lateral’ aberration.
It happens when the colors are present on the focal plane, but not all in the same point.
This type of aberration is more present toward the edges of the frame. This is something you wouldn’t find in the central part of the frame.
What Does Transverse Chromatic Aberration Look Like?
Transverse/Lateral Chromatic Aberration appears as sharp color fringing. It is found alongside high contrast edges of dark or bright areas.
The color fringes are complementary colors along opposite edges. Left side green, right side red, and so on.
Stepping down your lens corrects longitudinal aberrations, but it does not correct TCA.
How To Reduce Chromatic Aberration on Your Camera
The lens industry puts great effort into minimizing chromatic aberration in their lenses. They do this with low dispersion optical glass and optical elements.
You will find that more expensive lenses suffer less from these aberrations. This is down to better material used, and more money spent on research and development
Some less common lenses are better than others. Apochromatic lenses, for example, correct chromatic aberration.
But a certain amount of both LoCA and TCA is unavoidable. This is where post-production helps to eliminate the problems.
High-quality lenses exhibit much less chromatic aberration than:
- cheap lenses
- fast lenses when used wide open
- old legacy lenses
- cheap teleconverters and wide angle converters
Here are some tricks to reduce chromatic aberration in-camera:
- avoid high contrast scenes
- accurate focus to reduce the LoCA blur, making it look smaller
- stepping down your lens by 1 stop or 2, i.e., by using smaller apertures, to remove LoCA
- placing your subject in the middle of the frame to make it TCA free and crop later to regain a better composition
- exposing for the highlights and avoiding blowing them up
- avoiding to use the shortest and longest focal length on zoom lenses
- experimenting on different distances between you and the subject
- change your images to black and white
How to Correct Chromatic Aberrations in Adobe Lightroom
TCA is usually easier to correct in post-processing than LoCA.
In general, Adobe Lightroom lets you remove (or reduce) both with a few clicks.
In Adobe Lightroom, you can find both an automatic and a manual correction for CA. It’s under the Lens Corrections panel of the Develop Module.
Chromatic Aberration Automatic Correction
Nothing could be easier. Tick the box Remove Chromatic Aberration in the Lens Corrections -> Profile panel. Now let Lightroom do its magic.
Chromatic Aberration Manual Correction
Sometimes, the automatic correction does not remove all the Chromatic Aberration in your image. In these cases you can go to the Lens Corrections -> Manual panel.
Use the eye-drop in the Defringe section to sample the affected edges.
While viewing the image at 100% sample different points along the edges showing CA. Like this, you’ll get the best global result.
Repeat the procedure for both the purple fringing or red, blue, and green colors.
There’s also a manual way to correct CA. This consists of manipulating the amount and color hue sliders. You can find these in the defringe section of the Manual panel.
Those sliders control the width, in pixels, of the color fringe to correct and it’s color hue. They are available for both green and purple fringing.
You can also manipulate the sliders to further reduce, or completely remove, CA. In case the automatic and/or eye drop methods did not correct it.
When you use the manual method, do not only focus on the edges you are sampling. Check the rest of the image as well.
Finally, don’t push the correction too far. This could damage affect some other parts of your image.
How to Test Your Lenses for CA
Right click on the image below to download the chart I use to test my gear against CA. Print it or display it full screen on your monitor set to its max brightness.
Now you can start testing your lenses against Chromatic Aberration. This is the start of minimizing it in-camera. Take a shot of it and then preview it.
Below is the result I obtained with my Sony Rx100 Mk2, and the chart displayed on my computer.
The Sony RX100 Mk2 has TCA (corrected by the software). And by LoCA (corrected with the eye-drop method).
I have worked to maximize the amount of Chromatic Aberration in the image.
But the complete removal of CA in Lightroom was still two clicks away (see image below).
If Chromatic Aberration shows up in your photos, don’t panic! From reading this article, you now know several tips and tricks to get rid of CA.
You can minimize Chromatic Aberration on your camera. And you can correct it in post-production. Your photos will turn out the way you want them to.