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Tuesday, May 21, 2013

Straighten Up


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

This Article Features Photo Zoom
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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