What is chromatic aberration? Why does chromatic aberration matter? And most importantly, how can you remove chromatic aberrations in your image?
As an amateur photographer with five years of experience, I often get asked this from new photographers.
Chromatic aberration is a significant image-quality problem for every lens. If you are aware of what it is and truly understand it, the loss of image quality can be reduced entirely.
In this post, I will explain what chromatic aberration is, how to identify them, and the best ways of removing chromatic aberration them in digital photography.
Chromatic Aberration (via wikimedia.org)
What is Chromatic Aberration?
Chromatic aberration, also known as “CA” “color fringing,” is a color distortion in lenses that creates noticeable unwanted color fringing, like red, green, blue, yellow, purple, magenta, along the edges of objects in an image, especially when there’s a high contrast between light and dark objects.
Why Chromatic Aberration Occurs
Chromatic aberration is a common problem that every lens can have. It occurs when colors are refracted (bent) wrongly by the lens – depending on the lens glass that it is passing through, either all wavelengths of color don’t arrive at the same focal plane, or all wavelengths of color arrive at different points in the same focal plane.
Theoretically speaking, all the wavelengths of colors should be able to converge at the same focal point in the same focal plane after passing through a perfect lens, called the “circle of least confusion.”
In reality, the refractive index for each wavelength is different in lenses. Some wavelengths of colors converge at different/ unwanted focal points after passing through a lens, which leads to chromatic aberration to some degree in a lens.
The Two Types of Chromatic Aberration
There are two types of chromatic aberration:
- longitudinal chromatic aberration
- lateral chromatic aberration
Longitudinal Chromatic Aberration
It’s known as “LCA,” occurs when different wavelengths converge at various points along the horizontal optical axis after passing through a camera lens. Red, green, blue, purple, or a combination of these colors can show up around objects or in the center of the image. Longitudinal aberration often occurs at long focal lengths.
Lateral Chromatic Aberration
It’s known as “TCA” “transverse aberration,” occurs when different wavelengths converge to varying positions along the same focal plane after passing through a lens. Unlike LCA, TCA only shows up at the image’s corners with a high contrast area, not in the center, such as trees. The illustration below shows how transverse aberration occurs.
How to Identify Chromatic Aberration
Identifying chromatic aberration is easy. You can quickly recognize it as narrow, colorful lines, like blue, green, red, or purple lines along the high-contrast edges of the image or in the middle of the image.
You can also notice visible chromatic aberration as blurred colors in front of and behind the focus area of an image. And it disappears at a small aperture when you’re shooting.
10 Best Ways to Remove Chromatic Aberration
Chromatic aberration is a frequent problem, especially on very wide angle lenses and cheap lenses. But there are many ways to remove chromatic aberration so color fringing disappears while color and details are preserved.
1. Avoid Shooting High-Contrast Scenes
High contrast scenes, like around midday, are one of the leading causes of chromatic aberration. It is particularly problematic when shooting against the sun or having the darker subject against the too-bright sky.
An excellent strategy to avoid high contrast scenes is to change the background to something with less contrast or simply wait for the right time to shoot. Moving a subject from direct sunlight to shade, like under a tree, will help you reduce its effect when shooting outdoor portraits.
Less Contrast = Less Aberrations
For some shots, you often have to work in high-contrast situations. Still, the following methods will help you take control of high contrast scenes:
Fill Flash
Fill flash works well for close subjects in high contrast scenes. With flash lighting up shadow areas, you will have a more natural-looking image with minor post-processing. Flash can also highlight more details than the flat light but might create unwanted dark shadows in some areas of the picture.
Use GND Filters (Graduated Neutral Density Filters)
GND filters significantly reduce the exposure difference, especially when shooting landscapes. GND filters are pieces of high-quality glass that are half completely transparent and half darker.
By putting the darker section of the filter over a bright sky, you will decrease the difference in brightness between the sky and the subject for a well-exposed landscape picture.
2. Shoot RAW
Shooting RAW will allow you to quickly remove color fringing from your images in Lightroom, Photoshop, etc.
Unlike a JPEG file, RAW images are not compressed and contain a larger amount of image data and, as a result, are far easier to edit with post-processing software.
Moreover, RAW gives you much more creative freedom when shooting out since you don’t have to compromise your settings and framing.
3. Position Your Subject in the Center of the Frame
Chromatic aberration is generally more noticeable on the margins of the image frame, not in the center due to the curvature of the lens elements. By placing your main subject in the center of the frame, you’ll often have little-to-no chromatic aberration on your subject.
However, sometimes centering the subject is not the best composition idea, but you do have the option to crop your image to your favored composition in post-processing. This is so much better than struggling with chromatic aberration.
4. Choose the Right Focal Length
At its focal length extremes, zoom lenses usually cause more color fringing issues than a prime lens.
For example, if you’re shooting at 8mm, you’re way more likely to encounter chromatic aberration. A 24 – 200mm zoom lens usually has more prominent color fringing issues at 24mm and 200mm and less in the middle range.
Avoid shooting at the shortest and longest focal lengths of a zoom lens. Instead, shooting at a medium focal length, for example, around 30mm for an 18 – 55mm lens, should reduce the unwanted chromatic aberration.
For wide-angle shots, use a prime lens that usually brings less risk of aberration.
5. Change Your Color Image to Black and White
Chromatic aberration is essentially unnoticeable in B&W simply because there’s no color to distract you.
If the color doesn’t play a significant role in your picture, convert your photo into black and white, which will reduce or eliminate chromatic aberration.
Black & white is the cornerstone of photography. The small changes in tones make B&W very compelling. If you haven’t played with black and white, I encourage you to do so.
6. Stop Down Your Lens Aperture
Stopping down your aperture is one of the best ways to reduce chromatic aberration. Instead of working with an f/2.8 lens, try a small aperture like f/4 or f/5.6. Slow your shutter speed or raise the ISO to achieve correct exposure. By doing so, lots of chromatic aberration fringing will disappear.
7. Use an Achromatic Lens
An achromatic lens also referred to as an achromat, brings color into focus at the same points to avoid chromatic aberration. Achromatic lenses typically feature two optical components cemented together, producing a clearer image than ordinary lenses.
8. Removing Chromatic Aberration in Lightroom
Using Adobe Lightroom is a good way to correct lateral chromatic aberration. Lightroom features two options – automatic correction and manual correction to correct CA.
Automatic correction means letting the software do the work for you. This option is quite simple. Start in the “Develop“ section of Lightroom, open the “Lens Corrections“ window, click the “Remove Chromatic Aberration“ box, then the software will automatically correct CA for you.
If the software auto-correction can’t completely remove CA, use manual correction to eliminate CA on your own.
Just begin with the ‘Develop’ section of Lightroom, then the “Lens Correction” window as you did for the auto-correction; next, click the “Manual” button, find the “Fringe Color Selector,” and select the affected areas you want to make the change. The software will do the rest for you.
9. Use High-Quality Lenses
High-quality lenses usually have less chromatic aberration than cheap lenses. Avoid old legacy lenses or cheap teleconverters and wide-angle converters that will logically maximize chromatic aberration than high-quality lenses.
10. Use Cameras That Have In-Camera Solutions
Some cameras, such as Sony interchangeable lens cameras (SLT, NEX, ILCE), can minimize chromatic aberration on supported Sony system lenses automatically to a certain extent.
For example, Sony mirrorless cameras have an in-camera optical correction feature called “Lens Compensation,” which has three options:
- Shading
- Chromatic aberration
- and Distortion
Make sure that the option “Lens Compensation” – “Chromatic Aberration” is set to AUTO in the camera’s setup menu; the camera will automatically eliminate the color deviation at the corners of the screen.
Conclusion
Now you should better understand chromatic aberration, from what it is to how to get rid of it.
Although chromatic aberration can be a nerve-wracking problem for beginner photographers, you will never struggle with it once you know how to fix it in camera or Lightroom. You can even take great pictures with cheap lenses.
