Straighten Up

Try digital perspective control to take the oddities out of your tilted camera shots

In this photo of a church in Granada, Spain, you can see a few distortion problems. The horizon isn't quite level, although it's close. Also, the left portion of the church has a pronounced lean while the right portion is much less. The overall effect is a photo that isn't bad, but it could used some help.

There are a few technical elements that immediately stick out between amateur and professional photographs. Sharpness and exposure are obvious. Professional photos are always tack-sharp and well exposed. It's not that a professional is always perfect; it's just that they typically would rather get beaten over the head with a cast-iron frying pan than let anyone see one of their images that isn't both in focus and with a spot-on exposure.

Less obvious aspects are in the framing. You rarely, if ever, see a professional photo with distracting clutter in the corners and edges. While amateurs get a kind of tunnel vision as they look in the viewfinder, a pro, by training and experience, tends to take in the whole frame simultaneously and adjusts to keep the corners and edges free of elements that would detract from the photo, as necessary. There are also compositional elements like using the shadow as part of the composition, seeing a shadow as a shape rather than a literal shadow of some other subject in the image, and creating dynamic compositions by using the Rule of Thirds and other techniques (see Guy Tal's article "Creative Visual Tension" in this issue of Outdoor Photographer).

These are the elements that are 80% of the battle of making a professional-level photo. The last 20% is what separates good from special, and the alchemy of that last 20% is almost impossible to quantify. You know it when you see it and perhaps, more importantly, you know it immediately when you don't see it. That's when you can see that something is missing in the photograph, but it's not obvious what it is.

Tilted horizons and vertical lines that converge when they should be parallel fall into the last category. When was the last time you returned from a trip with photos where you had the camera tilted slightly upward, which created an effect of the building you were photographing looking like it was falling over? Now think about how many times you've seen that kind of tilted, askew look in a pro photo. Since the early days of image-processing software, there have been "one-click" solutions for fixing these problems, but those "fixes" could frequently do more harm than good to the photo. Software has progressed, and perspective repairs do much better today with fewer artifacts and silly-looking distortion so that now these one-click fixes are well worth using. As with any digital manipulations, every adjustment should be carefully evaluated to determine whether you've made the photo better or just different. Usually, straightening the converging lines in a building is going to make for a better, more polished photo. On the other hand, the converging forced-perspective look can be better in a lot of nature scenes as it makes for a more dynamic composition.

Before you set about correcting converging lines, consider the cause. You usually see this in photos where the subject plane and the sensor plane aren't parallel. No matter what lens you use—wide-angle, telephoto or anything in between—having the sensor plane tilted up in relation to the subject will result in converging lines and, if you're photographing a building, it will look like it's falling backward. Very wide-angle lenses also will cause this effect, but with the lens, part of the look is created just by the extreme wide-angle focal length and the distortion that goes along with it. Subjects in the distance are less affected, and the closer to the lens an element is, the more pronounced the distortion will be.

Here are some examples where a one-click fix worked and where it didn't. As you look at these images and try perspective repair on your own photographs, compare the "before" and "after" with a critical eye. Did you make it better or just different?

1) Auto Level
Not to be confused with Auto Levels, which corrects for exposure levels in your images, the Level function in Lightroom's Lens Corrections section automatically straightens your image vis-à-vis the horizon. This simple function works well, but the catch is that it needs a decent horizon to work with. If your photo doesn't have some sort of strong horizon, Lightroom is unlikely to be able to make any Level corrections. In this photo of the Granada church, we do have a strong horizon line, thanks to the retaining wall that runs across much of the frame. Lightroom used this line as its horizon and leveled the scene up to it. The change to the photo is minimal, and Level, while it gave us a nice base to work from, didn't do anything to correct the distortions elsewhere in the photo.

2) Auto Correct Vertical Lines
By clicking on the Vertical box, Lightroom has looked at the photo, found the vertical lines of the building and made them perfectly straight. This was quick and simple, but again, it wasn't perfect. The usual keystoning has occurred, which you can see at the bottom left and right edges. Also, we've eliminated the original image's distortion, but we've created new distortion—the leading edge of the church now looks oversized compared to the rest of the structure.

3) Lens Corrections
We're using the Adobe Lightroom 5 Beta to make adjustments to the image because improving perspective corrections was a big part of the new version of Lightroom. In the Develop module, there are new features under Lens Corrections > Basic. Notice the Enable Profile Corrections and Remove Chromatic Aberration boxes. Adobe suggests checking these boxes to give Lightroom the best ability to analyze and fix the image.

4) Constrain Crop
We could go ahead and use the vertical lines-corrected image and apply the Constrained Crop at this point. Constrained Crop would get rid of the gaps that were created at the bottom left and right. It's a great improvement to the original, but Lightroom gives us some other new controls to try.

5) Full Auto Correct
In Lens Corrections, you'll see that there's an Auto button. By clicking on it, we're giving Lightroom more license to work with the image. In the past, this sort of auto tool usually would be the most crude of instruments, prompting most of us to go to manual so we could fine-tune the adjustments. In Lightroom 5, that's pretty much just the opposite. By selecting the Auto button, we're actually telling Lightroom to consider all of the level and vertical line issues in this image and make the best compromise. In the Auto Corrected image, the lines aren't perfectly vertical, and the upper portion of the building isn't nearly as distorted as it was after applying the Vertical correction. There's still some cropping to the overall image due to keystoning, but it's much less than in the Constrain Crop image. Yet, the photo is much improved over the original. It's the ability of software to find reasonable compromises that makes "one-click" perspective corrections so powerful today. This photo has been transformed from a pretty good shot of an old building in Spain to a much more polished and professional-looking image. It maintains some distortion, but it's not nearly as distracting as it was in the original.

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