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Tuesday, May 21, 2013

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.

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