Correcting Converging Verticals and Lens Distortion in Photoshop and Lightroom
If you’re into architectural photography of any kind (interior or exterior), you’ve undoubtedly run up against the limits of your lens and/or the laws of physics.
Sometimes, you simply can’t keep your camera sensor parallel to your subject as it will either kill your composition or you can’t physically center yourself relative to the subject. Even when you think you’ve nailed it, you might find out in post-production that your shot lacks perfect symmetry. What can you do!?
You can either fork out $2000 for a wonderful tilt-shit / perspective-control lens and re-shoot, or learn a few tricks in Adobe Lightroom and Photoshop that permit for extensive lens corrections — fixes that only take a few seconds to apply.
Automatic Lens Correction
In Adobe Lightroom 3, there’s a great feature that allows you to correct for known issues with lenses of all brands. Every lens on the market has certain weaknesses when it comes to its faithful reproduction of a scene. Some are more prone to distortion and others to vignetting. A database of these issues permits “counter adjustments” to be made in post such as brightening the corners to remove vignettes or bulging a pin-cushion distortion inherent in a lens.
I find the removal of known distortions to be the most useful feature I find it really unbends a photo. The distortion is often unnoticeable in portraits but once you do correct for it, it becomes obvious. If you turn it off, it’s as if the photo is on curled paper.
When you shoot architectural shots like the one I posted above, you start to see how much distortion can exist, especially with wide angle lenses. Straight lines start to bend and bow and vignettes really start to darken the outline. Some of the issues in my photo arise from the camera position but others are simply the wide angle lens I have. This photo was taken at 15mm using the Canon EF-S 15-18mm lens. It’s a modern high-quality lens but it still suffers some distortion at 15mm.
In the Lightroom Develop module, I simply scroll all the way to the bottom of the settings panel to find “Lens Correction”. I start by just checking off, “Enable Lens Corrections”.
In a single click, a whole host of changes can be spotted. Can you see them in the comparison below? Look how much brighter the outer rim of the photo has become and how much straighter the top horizontal lines are now.
Photoshop has a similar tool but its automatic correction is not as dramatic given the profile I found and used. I can’t tell you which is more accurate.
Manual Lens Correction
Both Lightroom and Photoshop offer the ability to manually override the lens correction. Normally, I would only play with this to remove any remaining chromatic aberration (i.e. colourful fringing in bright highlights) as I don’t want to skew my photo unnaturally. However, if I know I had to tilt my camera upwards and want to fix converging verticals, I don’t hesitate.
In the case of my sample photo, the ceiling has converging vertical lines but they get smaller as they go down. I really wanted to make the ceiling area square so I used Photoshop’s “Custom” tab in the Lens Correction filter to make necessary changes. The dialog below doesn’t show the changes I made as it doesn’t save them. More on that later.
There’s just as much control in Lightroom but in a more compact interface. The benefit of doing these changes in Lightroom is that it’s all non-destructive “metadata” applied to your RAW file. Lightroom never copies you RAW file so you can always undo your changes and it won’t cost you any additional storage space. You can revisit your settings ant any time, make virtual copies to radically different treatments or save various inside a single photo by creating “Snapshots” in the Develop module. So go ahead, experiment a bit more.
If, however, you did a round-trip through Photoshop each time, you’d create a massive TIFF or PSD file and some filters like Lens Correction are not modifiable after they’re applied. If you have to edit your work in Photoshop anyway, this may not matter to you.
Here’s are the same custom lens correction controls in Lightroom:
Creating Custom Lens Profiles
It’s worth mentioning that Adobe offers a free software tool for Mac and Windows to create your own camera and lens profiles. These can then be shared and made available for others to use. You’ll notice in the Photoshop Lens Correction dialog that there’s effectively an online search engine to locate profiles for your camera and lens. If you can’t find your camera, you can select one that’s similar.
I won’t get into how to create a custom profile but at least you know now that it exists. I thnk the process consists of printing off a grid and photographing it several ways and then letting the software review those to create a new profile. Overall, it’s not for the faint of heart.
If you’re daring, give it a try by downloading the Adobe Lens Profile Creator.
Plan Ahead and Allow for Cropping!
The lesson I’ve learned with these tools is that I must plan ahead to ensure my composition can accomodate these adjustments. Most of these tweaks pull part of the photo away from its edge and thus requires a crop to remove blank spaces. If you move any of the sliders radically, expect a severe crop.
To illustrate this point, I’ve taken a photo where I intentionally used converging verticals to illustrate height. I then try to correct for the converging verticals in Lightroom to show how far you can push. This photo so is quite extreme so I moved the “Vertical” slider in Lightroom to -100 and still didn’t get perfectly vertical lines. Notice how much of the photo is lost both from the top and bottom.
If you’re only adjusting for converging verticals and you feel you need more control, there’s two other options found under the Edit > Transform menu in Photoshop. You can select “Perspective” or “Distort“. Perspective helps you keep your adjustment symmetrical while Distort lets you pull the four corners any which way you like. With some trial and error, you’ll probably find the right tool for the job.
Coming back to the before-and-after lead photo at the start, I used only the Custom Lens Correction feature in Photoshop to fix the non-square angles and odd bulges. Those controls were able to solve most of the issues while those that remain are due to me being slightly off centre when I took the shot.
Look again at the comparison image to see how much had to be cropped along the bottom. This was the “cost” of not getting right in camera. The photo still looks good without such a dramatic fix but this “correction” gave me the right-angles I had wanted in the first place.