Figure 1-33 Comparison of Angle of View on Camera Lenses

by and large, they are the cameras most used. For these reasons we shall limit our discussion of using different lenses to 35mm SLR cameras. Keep in mind, however, that the concepts discussed apply equally well to all cameras and lenses no matter what their size of focal length may be. Lens interchangeability is one of the great features of SLR cameras. SLR cameras have focal-plane shutters directly in front of the film so the lens can be removed and replaced at any time without fogging the film. Most makes of lenses and cameras are designed with their own exclusive method of lens attachment. Some use screw-in lenses; others use bayonet mounts. And each lens is either incompatible with or requires special adapters to fit other brands. Lenses for 35mm cameras are generally divided into two groups. The first group is a basic set of three. These are moderately wide angle, normal, and moderately long focal length. The second group is a variety of special lenses. This group of special lenses includes ultra-wide angle, extreme telephoto, shift lenses, variable focal length (ZOOM), and macro lenses. Most experienced Navy photographers who use a 35mm camera agree that a basic set of lenses is well worth having. Their choice of actual focal-length lenses is a far more personal decision. One may prefer a 35mm wide angle and a 200mm long focal length. Another photographer may prefer a 28mm wide angle and a 135mm long-focal-length lens. There are two occasions for changing lenses. The first is when your viewpoint or camera position cannot be changed. Imagine that you are aboard a ship and taking pictures of the coastline. To get a broader view of the coastline, you cannot move your camera position because the ship is on course. The solution is to change to a wide-angle lens. To get a closeup shot of an important section of the coastline, you obviously cannot move closer to the shore. You must change to a long-focal-length lens to bring the important section of coastline closer to you. The second time you would change lenses is when a different focal-length lens enhances your subject (remember the cow having lunch). This depends on your ability to change camera viewpoint, forward and backward, so you can fill the picture area with the subject. Using a long-focal-length lens reduces depth of field, makes the apparent effect of linear perspective less dramatic, and decreases the apparent distance between different subject planes. The use of a wide-angle lens has the opposite effect. It increases depth of field, exaggerates apparent linear Figure 1-33.–Comparison of angle of view on camera lenses. perspective, increases the apparent distance between subject planes, and may introduce image distortion. As the focal length increases, the image gets bigger and the angle of view becomes smaller. You cannot change the picture area produced on film by a 35mm SLR camera. The picture area is always 24mm by 36mm. Lenses for 35mm SLRs (except some ultra-wide lenses) all produce an image that completely fills the picture area. Along lens magnifies the subject image and not as much of it fits into the film frame area (fig. 1-33). Thus long-focal-length lenses cut down the area you see around the subject, and they, therefore, have a small angle of view. Short-focal-length lenses produce much smaller images from the same camera position than long lenses. The small image of a subject looks farther away and much more area surrounding it can be included in the picture area. A short-focal-length lens gives a wide- angle view. This is why short-focal-length lenses are called wide-angle lenses. 1-31