Transformations: Correcting perspective

Because most of us photograph from ground level (and therefore point the camera upward at tall structures), our pictures often suffer from increased optical distortion. By packing more information into a small frame, the optical system cannot help but distort some of the vertical and horizontal lines. The best way to avoid such distorted perspective would be to shoot horizontally, from an upper floor, opposite a tall building, which means that you're less likely to suffer from optical distortion because there's less reason to tilt the camera. But we are rarely in a position where we can do that, so it's back to street level and optical distortion.

In the days before software applications like Photoshop Elements, photographers had to spend upward of $3,000 to buy a perspective correction lens (also called a tilt-shift lens). These lenses come in 24mm or 35mm focal lengths, and allow the user to slide the front element...