Lens distortion is a potential problem for any photographer without access to a tilt shift lens, and not all of us have the ability or desire to dump a couple grand on one. There’s a lot of things that two grand could go towards besides a niche lens like a tilt shift. If you’re an architectural photographer, that is certainly a different story, but most people aren’t.
There are quite a few types of lens distortion, but this article is going to focus on perspective distortion. I’ve found, for photographers, lens distortion only becomes a problem once you discover what it is, and if you haven’t discovered it yet then I apologize in advance because now it will drive you nuts when you don’t want it! When I first started out, I had no idea that my lens distorted reality and therefore I never noticed it in my images. I remember when I first started posting photos to flickr when I was brand new photographer, I put up an image I took at a really old Methodist church. I took the shot from the second floor balcony, which unknowingly to me at the time was probably the best place to shoot when trying to get straight lines all throughout your image. Unfortunately for me, I tilted the camera down a bit, which caused the vertical lines in the scene to lean in towards the center of the image.
When somebody tried to point this out to me, I was befuddled. I looked and looked at the image, but I couldn’t see what he was talking about. He just told me that the lines weren’t straight! I wasn’t looking at the lines in the scene in comparison to the edges of the frame, I was just looking at the lines themselves. They looked pretty dang straight to me, and I was getting pretty ticked off at this guy! Eventually, he told me to compare the lines in the scene to the outer edges of the framing itself and that’s when I had that first “aha” moment with lens distortion.
It’s important to note that lens distortion isn’t good or bad in and of itself. Like most things, it just depends on how and when you use it, and whether or not you meant to use it!
If you are unfamiliar with what I’m talking about, here are a few examples of intentional lens distortion…
via Correcting Perspective Lens Distortion In Photoshop.