Hunter-Ch05.qxd
11-01-2007
02:28 PM
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REVEALING SHAPE AND CONTOUR
Do Lenses Affect Perspective Distortion? When most photographers first use a wide-angle lens, they decide that the lens introduces a great deal of distortion. This is not quite accurate. Camera position determines perspective distortion, not the lens. To prove this, we made every picture of the chessboard with the same wideangle lens. This means that we had to enlarge the image made at an intermediate distance somewhat, and we had to greatly enlarge the image made at a greater distance. Those enlargements produced images whose sizes match the one made with the camera closer. Had we used longer focal length lenses, we would not have had to enlarge those two images, but the shape of the chessboard would have been the same as the shapes in the three pictures we show. Choosing a lens of the appropriate focal length does allow us to control image size to make it fit the sensor size. Assuming we want the usable image to exactly fill the sensor, a short focal-length lens allows us a viewpoint that produces perspective distortion. A longer lens allows us to get far enough from the subject to minimize perspective distortion without having to greatly enlarge the image later. In each case, the viewpoint determines the distortion, not the lens. Extremely wide-angle lenses and inferior lenses may produce their own other types of distortion but not perspective distortion.
can greatly influence the other. A large light, for example, illuminates the subject from many different “positions� at the same time. In the rest of this chapter we will see how these two variables relate. THE SIZE OF THE LIGHT Selecting the size of the light is one of the most important steps in studio lighting. Time of day and weather determine the size of the light outdoors. The previous chapter discussed how adjusting the size of the light makes the edges of the shadows harder or softer. If two shadows record as the same gray, a hard shadow will be more visible than a soft one. For this reason, a hard shadow often increases the illusion of depth more than a soft one. When we understand this we have another way to manipulate the tonal values, and thus control the sense of depth, in our pictures. This seems to say that hard lights are better lights, but depth alone does not make a good picture. A shadow that is too hard can be so visible that it competes with the primary subject. Because we cannot offer firm rules about what size light is always best, we will explore the general principles in more detail.
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