Compose your picture and set the film speed lens aperture and shutter speed

Looking through the viewfinder on the top and back of the camera, you can compose your subject the way you like it. But you also must make sure that the film is receiving the right amount of light (exposure) to record the subject. The first step for correct exposure is to set your ISO number, or film speed, on the camera so the built-in light meter knows how much light your film needs. Most modern cameras set the film speed automatically by reading a bar code on the film cassette. On older or fully manual models, you must set the film speed yourself, often using a dial located on the top of the camera body.

Once the film speed is fixed, the light meter can measure light in the scene to determine how to set the camera for correct exposure. There are two settings to control light. One is the lens aperture, an adjustable opening inside the lens, measured in f-stops. A low f-stop number, such as f/2, indicates a wide lens opening that lets in a lot of light, whereas a high number, such as f/16, indicates a small opening that lets in much less light.

The other light-controlling setting is shutter speed, a measurement of how long the shutter (a curtain or set of blades located between the lens and the

Lens aperture, f-stop: pages 35, 38-41

Shutter, shutter speed: pages 57-60

Exposure modes: pages 81-85

Autofocus: pages 35-37

film) opens up to allow film to be exposed. The most commonly used shutter speeds are indicated as fractions of a second; a "slow" shutter speed (1/30) lets in light for a much longer period of time than a "fast" speed (1/1000).

The job of the light meter is to provide the right combination of f-stop and shutter speed to achieve correct exposure. In fully automatic cameras, or cameras in a program autoexposure mode (P), the camera sets the f-stop and shutter speed for you, often displaying the chosen settings in its viewfinder or LCD panel. In nonautomatic cameras, or cameras set in manual mode (M), you'll have to set f-stop and shutter speed yourself with guidance from the meter. Many cameras offer various other semiautomatic exposure modes, described later.

There's a lot to know about getting the right film exposure. But to begin with you may want to shoot a few rolls in automatic or program mode to become familiar with the mechanics of picture taking. Good exposure technique is covered in great detail in later chapters.

Focus and take your pictures. Once you've composed your picture and established the correct exposure, make your subject sharp by setting the focus, either automatically (autofocus) or manually; most cameras offering autofocus have a switch that allows you to choose either manual or autofocus. In most cameras, to use autofocus you push the shutter button halfway down; there is often an

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