What is Chromatic Aberration?

Chromatic aberration is a type of distortion where the lens fails to focus different colors of light at the same point. In photography, chromatic aberration is also known as “fringing” or “color fringing”.

Why it happens

Different colors of light travel at different speeds (wavelengths) and when they pass through the lens they can get refracted at slightly different angles. When this happens, high contrasting objects can have a blurry colored edge around them. This “fringing” can be red, green, blue, purple, or magenta in color.

In reality, there are no “perfect” lenses. If there were a perfect lens, it would focus all of the different wavelengths of light into a single focal point. Below is an example of a perfect lens with no chromatic aberration.

A perfect lens with no chromatic aberration

A perfect lens with no chromatic aberration

The red, green, and blue light are all refracted at the same angle and meet at the same focal point.

Types of chromatic aberration

In real lenses, light is not refracted perfectly. Depending on the design of a particular lens, it can display one or both types of chromatic aberration.

Longitudinal chromatic aberration

Longitudinal aberration (a.k.a. “axial color” or “bokeh fringing”) occurs when a lens cannot focus different colors of light at the same point on the optical axis. These aberrations show up as fringing around objects and can appear anywhere in the image.

Longitudinal chromatic aberration

Longitudinal chromatic aberration

In the image above, the green wavelengths are in sharp focus where the focal plane and optical axis meet. The blue and red wavelengths are both focused at different points along the optical axis creating the aberration.

These aberrations are the most often present in prime lenses with fast apertures. The effects are hard to fix in post processing, but can be greatly reduced by stopping the lens down.

Lateral chromatic aberration

Lateral (a.k.a. transverse) chromatic aberration occurs when a lens focus different wavelengths of light at different points along the focal plane. Lateral chromatic aberrations are only visible in the corners of an image where there is high contrast. Unlike longitudinal aberrations, it can’t be corrected by stopping a lens down. Most often, you’ll see lateral aberrations in wide-angle and fisheye lenses.

Lateral chromatic aberration

Lateral chromatic aberration

In the image above, the wavelengths are all out of focus. Instead of being spread across the optical axis, they are all focused along the focal plane.

Correcting chromatic aberration

If you still have lateral chromatic aberration after reducing the longitudinal chromatic aberrations by stopping the lens down, they can be easily corrected using software. Lightroom and Adobe Camera Raw both have simple lens correction tools. In most situations, chromatic aberration can be eliminated with a single click.

In Lightroom’s develop module, the lens corrections panel is on the right side of the window. Open the panel and check the box to Remove chromatic aberration.

Lightroom 5 - Lens correction panel

Lightroom 5 – Lens correction panel

The process is basically identical in Adobe Camera Raw. The sixth tab in Camera Raw is the Lens Corrections tab. The image below has the tab highlighted. Inside the corrections tab, check the box to remove chromatic aberration.

Adobe Camera Raw - Lens corrections tab

Adobe Camera Raw – Lens corrections tab

Lens design

In order to reduce the effect of chromatic aberration as much as possible, manufacturers are constantly attempting to make better lenses. Some lenses use special systems called achromatic or apochromatic lenses to reduce the effects of chromatic aberration.

In this type of setup, two or three glass elements with different amounts of dispersion are mounted together. The elements work together to bring all the wavelengths of light to a single focal point. Even the best apochromatic lenses can’t completely eliminate chromatic aberration, but they do greatly reduce its visible effects.

Achromatic doublet compound lens

Achromatic doublet compound lens

If you want a more in-depth look at chromatic aberration, I found a fantastic article. Click here to read it.

If you enjoyed the article, leave a comment or suggestion below. Thanks!

To continue reading on the same topic, here’s the next article on spherical aberration.