Unfortunately, it is one area we can’t always get around. This forces us to solve these issues later on in post-production.
For all types of aberrations you will experience with photography, read below.
What Are Aberrations in Photography?
An aberration is an imperfection in the way a lens focuses the light it captures. There are a few different types. These affect things like sharpness, focus, magnification, distortion, and color in your images.
When designers create new lenses, this is the biggest challenge to overcome. The presence of aberrations limits the lense’s performance in reproducing an image accurately.
In an ideal world, a lens designer would like a white ray of light to be realistically represented. This is regardless of its position.
No matter how hard they try, it doesn’t always turn out like that. This is especially true for fast wide-angle lenses.
Prominent aberrations distort the shape of stars. This is especially true towards the edges of the frame.
CAs are imperfections in the way a lens disperses different colors of light. This is similar in how a prism separates light into a rainbow.
Many lenses are pretty well corrected for chromatic aberrations, yet they still occur. This is especially true for faster lenses and capturing high contrast areas.
Chromatic aberration needs a little more information. You can find it here in our What Is Chromatic Aberration and How To Correct It article.
Monochromatic aberrations happen when lenses focus on a single color of light.
Spherical aberrations happen when using spherical glass elements in the lens. These shaped elements cause light to converge at different places on the sensor.
Lens design and the quality of glass material used in the lens cause this aberration. Even the placement of elements within the lens housing doesn’t help. This reduces the focal strength and affects the image’s resolution and clarity.
Again, this area is a little more complicated. You can get more information from our What Is Spherical Aberration? article.
Comatic or Coma aberrations get their name from their comet-like shape. This is when they represent point light sources in an image.
This aberration occurs when a single point of light enters a lens at its edge, rather than the center.
They are also more obvious at the edges of frames in images captures with wide apertures. Thus, raising your f/stop can help to combat this problem.
Many photographers assume a coma aberration with distorted light sources. It can be far more complex than this simple aberration issue.
External coma aberrations occur when the tails point away from the center of the image. The opposite are internal coma aberrations.
Lenses can often decide that speed is more important than aberration corrections. The Voigtländer 50mm f/1.1 Nokton is a good example of this.
Tangential and Sagittal Astigmatism
You may have heard of astigmatism when it comes to problems with the human eye. This aberration causes light sources at the edges of the frame to stretch in a line shape.
Tangential Astigmatism is when the lines run from the top-right to bottom-left. Or vice versa. Sagittal Astigmatism shows the line shapes running from top-left to bottom-right.
These are some of the most difficult aberrations for lens designers to correct. Within astrophotography, these aberrations are some of the most common. Even when using expensive lenses.
Raising your f/stop will help to minimalize these imperfections.
Field curvature aberrations occur when the lens doesn’t focus the light onto a flat plane. Instead, it focuses on one that is an imaginary curved surface.
The sensor of most cameras is flat unless you are using a large format camera. What you will see are imperfections in the focus across an entire image.
Images that suffer from this aberration seem as if the center is in focus, while the edges aren’t. This can also happen in the reverse.
Older lenses suffer from this aberration more than more modern lenses.
Floating Elements and Effective Focal Length Change
Floating elements are part of the inner lens. They adjust their position when focusing on subjects close to the lens. These help correct aberrations, especially found in the higher-end lenses.
There is an alternative to this group system. The lens design may allow for other elements within the lens to move. This is when focusing on closer objects.
The problem is that the effective focal length reduces when using a small focal distance.
An example of this is the 70-200 mm f/2.8 zoom lens. The effective focal length dropped to 145 mm when focusing on a close object. It was a method that allowed sharp focusing on those closer subjects.
Distortion is another very common aberration found in photography. This aberration occurs when the lens projects a wider scene across a sensor or film plane.
The distortion can happen vertically or horizontally. Barrel distortion is when the captured scene looks smaller at the edges of the frame than in the center.
Distortion aberration is more noticeable when capturing straight lines. In images with distortion aberrations, the lines bend and curve. This creates an unrealistic scene.
Some lenses even show signs of both types of distortion aberration. This distortion type is a mustache distortion. The name comes from its wavy nature of line representation.
Distortion doesn’t tend to present a huge problem as we expect it a lot more. We trade off a wide field of view for a change in represented objects. If the distortion is over-the-top, it can be distracting and painful to look at.
You can find more information and examples in our What Is Lens Distortion? article.