A Problem of Perspective
A Problem of Perspective. Notice that the posts nearest the left and right edges of the image do not appear vertical.

In my previous article on tilt-shift lenses I talked about tilt and how that affects the plane of focus.  It is a pretty great feature, and it is (I believe) behind the increased energy we’re seeing in the press and from camera manufacturers about these lenses. But it’s far from the only trick these little wonders can perform, today we’ll talk about the most basic use of  shift (including what the large format guys would call rise and fall), to correct perspective in a photograph.

Perspective control using shift has been a staple of architectural photography for decades. When photographing a building from ground level, perspective causes the top of the building (which is farther from the camera) to show smaller in the image than the bottom. In seeing the real world around us this effect appears quite natural, but in a photograph the effect often makes the building appear as if it were falling over backwards. What we need for the image to “appear” more natural is a way to reduce the perspective-induced distortion of the shape of the building.

Same scene before correction
Same scene after correction. The result isn't perfect (these examples are handheld), but you can see a significant improvement in how parallel the posts appear.

This problem isn’t limited to architectural photographers. Nature photographers like myself sometimes run into perspective issues as well. While   the lack of straight lines in the natural landscape often obscure the distorting effects of perspective, when I photograph in redwood forests the problem is often inescapable.

With a tilt-shift lens, the solution to “the building problem” is simply to displace (that is, shift) the front element upward relative to the back of the lens, and then recompose the image. (In the example image, perspective is leaving the posts bent in the other direction, so I lower, rather than raise, the front element to compensate.) In the examples, I shifted the lens about four degrees. While far from perfect, the corrected image looks more rectangular, the vertical posts appear vertical in the image.

It should be noted that this sort of perspective correction can be achieved in the digital darkroom as well, using Adobe Photoshop, DXO Optics, or PTLens. In Photoshop the “Lens Distort” filter can be used to correct for this as well as many other types of distortion at the same time, including chromatic aberration, pincushion and barrel distortion. Photoshop’s crop tool also provides perspective correction by use of the perspective checkbox, but I find the filter easier to control. (Unfortunately, Apple Aperture and Adobe Photoshop Lightroom do not yet provide tools for perspective correction.)

There are places for both tools. Digital correction offers a lot of after-the-fact flexibility, and in some cases, particularly with older tilt-shift designs, may produce sharper results. On the other hand, optical correction gives you the ability to “see what you’re shooting” at the time, and with modern optics such as the ::amazon(“B00009XVCD”,”Canon 24/3.5L TS-E II”)::  or new Nikon equivalents may produce superior results.

There are far more uses for tilt-shift optics than I’ll be covering here, as well as other challenges and limitations in using them. But, it’s my hope that these introductory articles begin to give you a sense of what all the fuss is about, what abilities tilt-shift lenses bring to the world of 35mm digital SLRs, and whether those abilities are something you can make use of in your own work.

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This Post Has 3 Comments

  1. Joe – great article.

    I would love to see some examples of photographs that include tall buildings and tilt-shifts that bring them back into correct perspective … what are the limits on that kind of thing?

    Also, I’ve seen really cool tilt-shift work from people like Vincent Laforet – which gives objects in the picture a toy-like, or miniature, appearance. Can you explain how this is done?

  2. Bill: I’ll put up more samples in a coming post. There are limits–just of the optics, usually, you get more distortion as you shift the lens further, you also get light falloff. (That tends to work out fine for buildings, where it often darkens the sky). But the sort of perspective changes in the dining room shot, in terms of visual angle, are perhaps half of the usable range of the old Canon 24mm TS-E.

    The miniature photos are pretty neat, and yeah, those deserve a separate post. I suspect that really getting a good “miniature effect” also requires a little bit of color/tonal secret sauce, but I really need to try it out, I just haven’t.

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