You've heard that a portrait lens is the one with a focal length of 50mm or above and that wide angle lenses create a distorted image when used for portraits. This article will try to help you understand and overcome that prejudice.
What Is a Portrait?
Portraits of people can be all kinds of images, from the paintings of the masters of old to the masters of photography today. It's an image of a person fit in a frame of a certain geometry. The portrait is not just the head of the person. There's a special term in photography for that: a headshot. A portrait can be a full-body image too.
'Wide Angle Lenses Distort the Face,' They Say
This is where the misconception comes. In theory, a wide angle lens should capture more of the view in front of the camera than a longer lens, which means it will change to a certain extent the viewing perspective from what we see with our own eyes. Objects that are close to each other will look farther apart with a wide angle lens. It will also have different depth-of-field properties per aperture: wide angle lenses have a deeper depth of field than longer focal lengths at the same aperture. For this reason, the blur of the background and the foreground (assuming the subject is in the mid-ground) is more prominent with longer lenses.
"OK, but wide lenses distort the image. This is why they are not liked for portraits; it's not the depth of field or what they see." This is the common complaint.
Why Is There Distortion With Wide Angle Lenses?
If you have shot with a wide angle cinema lens, it will change your mind about what you call "distortion." The optical defect that makes most photographers avoid using wide angle lenses is a radial-looking distortion that is different from the perspective distortion of the lens. The radial distortion is making the image look as if areas closer to the periphery of the lens are bent inwards or outwards.
To illustrate that in a different way, let's suppose we have a wall, which we look at from the side with a 50mm lens on a full-frame sensor (a) and with a wide angle lens on the same sensor. A wide angle lens without radial distortion (b) will change the perspective, as you see in the middle, while a radial distortion defect (c) will bend the lines that are closer to the periphery of the frame, and thus, you will no longer have straight lines in these areas.
There's a radial distortion with longer lenses too, but few people complain about it. That defect is not supposed to be there. As making a lens without or with a minimal radial distortion is an expensive process, most manufacturers decide to leave it, and today it's used for artistic purposes. If you purchase a quality wide angle cinema lens, the radial distortion there is very small if not almost eliminated. If you take the radial distortion seriously and correct it with any lens, you use your will start loving the different perspective of the wide angle view without the lines bending and will start to incorporate that look more and more in your images.
In the following video, you will find tests with different 14 mm cinema lenses and the radial distortion (called simply "distortion" in the video) will be close to none. You may be surprised how a wide angle view should normally look compared to what most still lenses do today.
How to Deal With Wide Angle Lenses' Radial Distortion?
The obvious remedy is to buy lenses with almost-eliminated radial distortion, but if you can't afford them, learn how much your lens is distorting the image, as it's different from lens to lens. There are two methods, which work best if they are both applied: compose accordingly and fix the rest in post.
Important Things Should Be Away From the Edges
In most cases, wide angle lenses tend to deform the areas close to the borders of the frame. If you have objects there, whether these are human faces, limbs, or rear parts of the body, they will look bigger than normal. To avoid that, keep important objects away from the edges of the frame, also because you may need to crop these areas out in post.
Fix It in Post
You can either crop out the border regions or try to correct some of the distortion to an extent that it's bearable, which will inevitably make you crop some of the pixels out.
Use a Camera With More Resolution
If the image is heavily distorted, you can crop out some of it and leave the normal-looking part without losing much of the resolution that is usually used today.
Avoiding wide angle lenses is avoiding the defects they are built with. Knowing how to use them will help you take advantage of the environment you see with your own eyes. Including more of the environment tells a different story and lets the viewer's eyes wander around, enjoying the details, especially if they are masterfully presented.