Accurate exposure is important in producing a high-quality photograph, and it is critical when you use a slide film. Exposure is the amount of light reaching the film. Each film requires a specific amount of light to produce a picture of the proper brightness. How much light a film requires depends on its speed. The versatility of your camera enables you to shoot pictures at sunrise, during a blizzard or rainstorm, in your family room, or at a night baseball game.

For such unusual lighting situations, a light meter is a must. Most 35 mm cameras have built-in meters. The built-in meters of SLR cameras indicate the shutter speed and aperture required for correct exposure. Those cameras that set the aperture and shutter speed are automatic-exposure cameras. Those that leave it up to you to set the shutter speed and aperture are manual exposure cameras. Many cameras offer both automatic and manual exposure.