So, you’re on vacation in a city with great architecture, you snap a photo of grand design and glance at your camera’s screen without paying too much attention. After uploading the photos to the computer you decide to review your images. You notice that every building is starting to resemble the leaning tower of Pisa. The vertical and horizontal lines are curved, buildings appear to be falling away from you. These are optical distortions or aberrations (remember that word, you’re gonna see it a lot), and today I am going to address the barrel kind.
The ground is level; but the Washington Monument is leaning inward
Now, barrel distortion is easy to understand, just take any photograph and imagine it wrapping around a ball. Whether this effect is good or bad I won’t say, it’s subjective. People drop a lot of cash for ultra wide-angle lenses or fisheye lenses to get an extreme barrel look. Nonetheless, barrel distortion is a failure in the lens to reproduce straight lines as they appear to our eyes. Barrel mostly occurs in wide angle lenses or zoom lenses set on the widest end. It can also happen with standard lenses (50mm) when the focal distance (camera to subject distance) is very short.
So I should just buy the expensive professional lenses to escape this problem?
Unfortunately no, even the big boys suffer the same fate. Distortions still exist, though they are usually minimal compared to the lesser expensive lenses. When shopping for a lenses, read multiple reviews, talk to your local camera shop guys (not the big box places), and rent the lenses. ”Perfect” lenses are rare gems and when you find one you will never let it go.
Barrel Distortion
What do I do with my current lenses?
When using my standard zoom lens (24mm-70mm), I usually refrain from using the widest focal length at 24mm cause I know I’ll get some barrel. I tolerate this because I love this lens, it produces super sharp images and I use it for almost everything. I simply just zoom in a bit (around 35mm) and take a few steps back to snap that photo. I recommend you take a couple test shots of any object with intersecting lines (preferably straight) to find that sweet spot on your lens.
Is their any kind software that can correct the distortion?
Yes, Photoshop CS2 and newer, Photoshop Elements 5.o and newer have lens correction filters where you can manually adjust the distortion. Just google “lens distortion (you photo-editing software)” for a how-to demo. There are free options like gimp that have distortion correction ability. You can also find automated corrective software like PTiens or DxO Labs.
That’s it for today, please post any comments or questions and join me every Techie Tuesday.
Peter Pechacek is a photographer and filmmaker in Orlando, Florida. He is new to the blog and will be contributing weekly on Techie Tuesday
