All You Need to Know About Lens Aberrations in Photography
An Aberration occurs due to the way the Lens focuses light. They happen because the rays of light passing through the lens fail to converge at a different point.
Despite all the advances in technology, there has yet to be a lens made that will not produce Aberrations at some point. But if you are familiar with the different types of aberrations that are out there, you may be able to avoid them. This article will review the aberrations you may encounter so you know what to look out for.
What are the Types of Aberrations?
The two main types of aberrations are chromatic and monochromatic. Here’s a bit about each.
Chromatic
Chromatic aberrations are also known as color fringing. They occur when the lens cannot focus various wavelengths of color at the same point. It disperses the colors in a prism-like effect.
While designers have made updates to reduce the occurrence of chromatic aberrations, they still occur in faster lenses and in high contract areas. The produce a color fringe at the edge of the image.
Chromatic aberrations can further be broken down as follows:
Longitudinal Chromatic Aberration: This is a type of bokeh fringing that happens when wavelengths of color don’t converge at the same point when passing through the lens leading to color fringing around the subject. They are more likely to occur with fast lenses and wide aperture settings.
Lateral Chromatic Aberration: Also called transverse chromatic aberration, this occurs when the light enters the lens at an angle that causes different wavelengths of color to focus on the same plane in different positions. They are visible on the edges of the frame and can only be fixed in post-production.
Monochromatic Aberration
Monochromatic aberration results when a lens can’t focus a single color of light. It is due to imperfections in the camera’s optical system.
There are five different types of monochromatic aberrations as follows:
Spherical Aberration: These occur when spherical glass elements in the lens cause the light to converge at different places. The lens will refract more light that enters near the edge as opposed to the light that enters near the center. In addition to being caused by an error in the optical system, this can also be due to the lens design and the materials it made of. The risk of aberration can be reduced by stopping down the aperture. It’s also less likely to occur in wider focal and telephoto lenses.
Comatic Aberration: This occurs when a single point of light enters the lens at its edge rather than its center. This causes the lens to be unable to focus light rays at the same point causing them to flare out and produce a look that resembles comas at the edge of the frame. It can be avoided by raising the f/stop.
Tangential and Sagittal Astigmatism: These result when rays of light enter the lens at the sagittal plane, so they are focused on at different points along the tangential plane. This causes a distortion at the edge and corners of the image. They are more likely to occur in lenses with an optical design and you can reduce the risk by raising the f/stop.
Field Curvature: Field curvature happens when the lens focuses light onto an imaginary curved surface instead of a flat plane. It causes focus issues across the images. It is more likely to occur in older lenses. Stopping down a lens can reduce the effect.
Distortion: Distortion occurs when the lens projects a wider scene across a sensor or film plane. It can occur vertically or horizontally, and it will be most noticeable when you are trying to capture straight lines. Depending on the type of distortion you get, the lines may appear bowed at the center, at the edges or wavy throughout. It is more likely to happen in zoom lenses and the risk may be reduced by changing the position of the lens when zooming or focusing.
Aberration can be a desired effect, but in most cases, you are better off without it. Now that you know the various types and why they can occur, you can reduce the risk of them appearing in your photos. Here’s to a future of great photography!
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