Perspective Control

Most of the pictures we take, whether consciously or unconsciously, are taken head-on. In that mode, the back of the camera is parallel to the plane of our subject, so all elements of the subject, top to bottom, and side to side, are roughly the same distance from the film or digital sensor. Your problems begin when you tilt the camera up or down to photograph, say, a tree, tall building, or monument. The most obvious solution, stepping backwards far enough to take the picture with a longer lens or zoom setting while keeping the camera level, isn't always available. You may find yourself with your back up against an adjacent building, or standing on the edge of a cliff.

Indeed, it's often necessary to use a wide-angle setting and still tilt the camera upwards to avoid chopping off the top of your subject. Figure 2.1 shows the relationship between the back of the camera and a monument when the camera is held perpendicular to the group. Notice that both the top and bottom of the subject are cut off.

Figure 2.1. When the back of the camera is parallel to the plane of the subject, it's sometimes impossible to include the entire subject in the photo.

Figure 2.1. When the back of the camera is parallel to the plane of the subject, it's sometimes impossible to include the entire subject in the photo.

Switch to wide-angle mode and tilt the camera to include the entire subject, and you get the distorted photo shown in Figure 2.2. The monument appears to be falling back, and the base appears proportionately larger than the top, because it's somewhat closer to the camera.

Figure 2.2. In wide-angle mode, tilting the camera makes the monument look like it's falling backwards.

The traditional workaround to this dilemma is one that's generally available only to those who do a great deal of architectural photography. The solution for 35mm photographers is to use something called a perspective control lens, an expensive accessory which lets you raise and lower the view of the lens (or move it from side to side; perspective control can involve wide subjects as well as tall) while keeping the camera back in the same plane as your subject. A more sophisticated (and more expensive) solution requires a professional camera called a view camera, a device that usually uses 4 x 5-inch (or sometimes larger or smaller) film, and has lens and film holders that can be adjusted to any desired combination of angles. Some perspective control can be applied in the darkroom by tilting the paper easel to compensate for image tilt (although the need to use very, very small f-stops to achieve the necessary depth-of-focus limits this technique). Those who can't afford such gadgets, or who own digital cameras without interchangeable lenses, appear to be left out in the cold.

That's where Photoshop comes in. You can make some reasonable adjustments to the perspective of an image within your image editor. Often, the manipulations are enough to fully or partially correct for perspective distortion. There are four methods you can use in Photoshop CS2, and we'll look at all of them.

No-Brainer Correction with the Grid

This section explains a basic perspective correction method you can use to fix a selection in your photo, using Photoshop's Grid as an aid. The procedure assumes that your image is oriented correctly (that is, it doesn't need to be rotated). Just follow these steps using the original image medinaceli.jpg from the Course website (www.courseptr.com/downloads), or use an image of your own.

1. Open the file medinaceli.jpg in Photoshop. The image will look like the one shown in Figure 2.3.

Photoshop CS Mastery

Photoshop CS Mastery

Artists, photographers, graphic artists and designers. In fact anyone needing a top-notch solution for picture management and editing. Set Your Photographic Creativity Free. Master Adobe Photoshop Once and For All - Create Flawless, Dramatic Images Using The Tools The Professionals Choose. Get My Video Tutorials and Retain More Information About Adobe Photoshop.

Get My Free Videos


Post a comment