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in your perspective, the parallel top and bottom lines of the front and the side appear to be diagonal lines. At the point where the horizontal lines appear diagonal in the field of view, you can easily create depth in a two- dimensional picture. This is called keystoning: fram- ing an image, such as a building, so that the parallel top and bottom lines become diagonal, converging to- ward a vanishing point and creating depth.

Besides creating volume, these converging lines can take the viewer’s eye to a subject or important el- ement of the picture. Our eyes naturally follow these

leading lines, extending them even if they don’t con- tinue on their own. By creating a focal point, you can lead the viewer to the main element of the shot. (See Figure 4-12.)

Use of Selective Focus Another way to create a sense

of volume within the frame is to have well-defined areas of focus. This technique is particularly useful when working with longer focal lengths that tend to

flatten a shot by compressing perspective. A shot of a subject walking down a crowded street, as seen through a telephoto lens, would not highlight the subject if all the faces in the shot were equally in fo- cus. By finding ways to decrease depth of field (shooting with a lower f-stop, perhaps, or standing back and zooming in), you can bring the subject into sharp focus and have both the background and the foreground drop out of focus. This shallow depth of field creates the look of depth and better expresses

the distances between elements in the frame. Even without a foreground, this technique can greatly en- hance the three-dimensional qualities of any picture. (See Figure 4-13.)

Effects of Focal Length

As focal length changes—the lens is zoomed in or out—many things change in the resulting picture. The most basic change is the size of the subject: it gets

Figure 4-11 Even though this railroad track is the same width all the way to the horizon, it appears to narrow as it re- cedes into the background, thus creating a vanishing point.

Figure 4-12 The angle here causes the train to be key- stoned and the other parallel lines to converge on the vanish- ing point and lead the eye to the central element of the im- age—the exit to the outside world.

Figure 4-13 By defocusing the foreground and back- ground, the subject in the midground—the artistic writ- ing—easily dominates the picture.

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larger as the focal length increases (zooming in). This magnification of the subject also has other effects in the overall picture. As the field of view narrows (the fo- cal length increases), the quantity of background de- creases as its size increases. Because the field of view is in the shape of a cone, as you zoom in, the rate of size increase for the background is much faster than either the foreground or midground of the picture. This vi- sual effect is known as compression. Objects at differ- ent distances from the camera and in line with each other appear to become closer to one another as the field of view narrows (the background seems to be moving forward), even though their sizes relative to each other never change.

This phenomenon can be used to great advantage by the photographer. For example, in a movie where the hero is running down the street toward the camera while being chased by a truck, a telephoto lens (long focal length) makes not only the hero appear large but the truck as well. The compression of perspective in the shot can make it look as though the truck is only inches from the hero when in reality the truck could be 100 feet away. The same shot done with a wide field of view would show the truck’s position more clearly and not have the same dramatic effect. The drawback to the zoomed-in shot, however, is the perceived speed at which the truck is closing in on our hero. Because of the compression, even if the truck is rapidly gaining on him, the truck’s size barely changes. Image size doubles in reverse proportion to the distance change. For the truck to double in size, it would have to come half again as close to the camera as it is. For a telephoto shot, that could be quite a distance.

In contrast, at a very wide field of view just the op- posite effect of compression occurs. In wide-angle shots, things in line with the camera tend to appear much farther apart than they really are. If the object of our truck chase is to see the speed at which the truck is closing in on our hero, the wide shot would do it. With both elements close to the camera (our hero is still the same size in the frame), the oncoming truck could easily double in size within a second or two (halving the already short distance to double in size), thus exaggerating the speed. These effects can be used to bring even static objects closer together or farther apart in a picture. (See Figure 4-14.)

Distance

In place of focal length change, you can substitute camera distance to change the size of the subject. By simply moving the camera closer to the subject, you increase its size in the frame. In the early days of pho- tojournalism, when each lens had one fixed focal length, the shooter had to walk to or from the subject to change the size of the image. Many people still refer

Figure 4-14 For both pictures, the girl in the foreground is framed in a medium shot and the boy in the background is the same distance from her. Only the photographer’s dis- tance and focal length changed. For A, the shooter stood close and used a wide angle to exaggerate distance. For B, the shooter stood farther away and used a telephoto angle to compress distance.

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