We all want a camera with as many megapixels as possible. But, there is much more to photo quality than resolution. From blurring to poor composition to chromatic aberration, there are many things you need to avoid in order to get great quality photos.
One such problem that you will come across often is lens distortion. If you’re a beginner photographer, chances are you won’t even notice it. But, it’s a good idea to learn what it is and the steps needed to address it.
What is lens distortion?
We say a photo is “distorted” when the lines and shapes look distorted. This happens because of problems with your lens or because of how the lens is designed.
A lens is made up of many optical elements that refract and bend light rays. Sometimes the geometry of a lens can cause distortion in the image. Distortion is common in low-quality lenses, but even expensive lenses can suffer from distortion.
If you’re a fan of wide-angle lenses, you’ll know that distortion is typical of them. This is because the camera sensor’s field of view is usually smaller than that of a wide-angle lens, so the edge of images looks crooked. Regardless, there are several benefits to having a wide angle lens. Fisheye lenses are designed to distort photos on purpose.
Types of lens distortion
Before knowing how to correct lens distortion, you need to know the types of distortion. Different types of distortion will require different correction techniques.
There are two main types of lens distortion.
This type of distortion occurs due to the optics of your lens. A standard lens is supposed to be rectilinear, where straight lines appear as straight lines without any distortion. However, if a lens is curvilinear, straight lines appear curved. A fisheye lens is the perfect example of a curvilinear lens.
Although standard lenses are designed as rectilinear lenses, all lenses suffer from varying degrees of distortion.
Optical distortion can occur in three ways.
In this type of distortion, the straight lines protrude outward, taking the shape of a barrel. Barrel distortion frequently occurs with wide-angle and wide-angle zoom lenses because their field of view is typically larger than the camera’s sensor. So the corners end up squashed into the frame.
When your lens has barrel distortion, images look like they’re stretched in the middle but squeezed in the corners.
Imagine a pincushion – you can see the pin pulling the corners inwards. Similarly, you’ll notice straight lines bending inward in a pincushion distortion. It seems like the exact opposite of barrel distortion. And the culprits that cause it are the opposite of wide-angle lenses: telephoto lenses, especially zoom ones.
A telephoto zoom lens disproportionately magnifies objects in the corners of the image, so you’ll see stretched corners but a pinched center.
This type of distortion is a combination of barrel and pincushion distortion. In mustache distortion, the straight lines at the corners curve inward while those in the center jut outward, resembling a mustache.
It’s a complex distortion that’s quite difficult to correct, but you’re more likely to find it only on older lenses.
This type of distortion has nothing to do with your lens. Instead, it happens due to the position of the camera and the distance of the subject.
Extension distortion (wide angle)
Have you tried using your wide angle lens to take portraits? You probably would have hated the result. A wide-angle lens can make faces appear abnormally large. But this is not the fault of the wide angle lens. The problem is that you are too close to your subject.
Generally, objects that are very close to you will appear larger. This is because you tend to stay too close to your subject with a wide angle lens. When you use a telephoto lens, you are forced to move away from the subject. That is the reason why telephoto lenses are one of the preferred lenses for portrait photography.
In short, stretch distortion widens the distance between the foreground and background.
Also, when you use wide-angle lenses to photograph tall buildings, they tend to appear wide at the bottom and merge at the top. This happens due to the viewing angle, with the part closest to you appearing disproportionately larger.
Compression distortion (telephoto)
In compression distortion, objects farther away appear unusually large. Essentially, it is the opposite of extension distortion and occurs in telephoto zoom lenses.
Compression distortion closes the distance between the foreground and background, making the image appear compressed.
How to correct lens distortion
You can correct common distortions like barrel and pincushion with post-production software. For example, Lightroom has a lens correction option. When you check Enable Profile Corrections, the software can find your lens in the metadata database and automatically apply the correction. Here is a guide on using lens corrections in Lightroom.
Mustache distortion, on the other hand, will require special software to correct.
To correct perspective distortion, your best bet is to check the distance between you and your subject and adjust accordingly. For example, do not get too close to the subject when using a wide-angle lens to avoid spread distortion. And for telephoto lenses, opt for a wide aperture so that background details are out of focus.
If your image is badly distorted, you can use the Transform tool in Lightroom to fix it. It works well for perspective distortion.
Using distortion artistically
You can certainly leave your image distorted and call it artistic freedom. Lenses like fisheye and tilt shift are made for this purpose. It’s good to know the type of distortion you’re dealing with and then decide what to do about it.
In the end, it’s up to you as a photographer to decide how you want your images to look. But know the rules before you break them.
Learn the basics to avoid lens distortion
All lenses have some form of distortion due to their design. It’s not a big deal, but it can be annoying. However, you can easily avoid this by paying attention to the distance and angle from which you are shooting. Also, invest in good quality lenses to reduce distortion in your photos.
If all else fails, you have post-production software to your rescue.