Stop the Chromatic Aberrations - Learn To Avoid This Issue

I’m sure you’ve seen the ghostly appearance around objects or people in a picture. This colored halo is chromatic aberration or color fringing. It usually appears as a purple, green or red outline or figure. This article addresses the causes of chromatic aberration and how to avoid it while shooting and in post-production.

What is Chromatic Aberration?

When the camera lens can’t focus the light wavelengths on the image sensor, a halo or fringe appears around objects. This optical illusion is chromatic aberration and it usually occurs in high contrast settings or when using a wide aperture.

While color fringes can be caused by lens flare or the sensitivity of the camera to the different wavelengths of light, chromatic aberration is the most common reason for its occurrence.

It’s Just Physics

If we think of a DSLR lens as a piece of glass it is easier to understand. The refraction, or bending, of light when it strikes the lens disperses the different wavelengths which form colors. But this causes the sensor to misread colors in different places and thus form chromatic aberrations.

Chromatic Aberrations and Camera Lenses

This problem can be lessened by minimizing the divergence of light waves. The common 18-55mm kit lenses, known as an achromatic lens design, are the least expensive way to resolve this issue. By using a second lens with a different dispersion than the main lens the light rays are converged to correct both the spherical and chromatic aberrations that happens when it goes through the first lens. However, this process is not perfect. An apochromatic lens design is used in higher end lenses where a third element, correcting even further aberrations, is added.

Other lenses like the Canon EF 70-200mm F2.8L or the Nikon 70-200mm f2.8 ED contain glass which doesn't disperse the different wavelengths as much so the problem is minimized. However, low dispersion materials like fluorite are expensive driving the lens cost up, and therefore driving up the cost of the camera itself.

Out in the Field

If you avoid high contrast situations it lessens the imperfections of optic design. If you get some fringing close the aperture at least one stop. Visible aberrations will be lessened.

Don’t use the extremes of your zoom lens. A zoom lens functions better at the middle focus lengths, such as when using a 70-200mm zoom, shoot at 135mm to get better results than at 200mm.

Avoid super zoom lenses if at all possible. On the wide end you will get awful chromatic aberrations. Instead buy some prime lenses--they are optimized to reduce chromatic aberrations and are a lot less expensive and heavy than a super zoom lens.