The photographer views the subject through the camera lens rather than through a separate viewing lens. A mirror between the lens and the film reflects the image to the viewfinder. When the shutter release button is pressed to take a picture, the mirror lifts out of the way to allow the light to expose the film. Thus, the photographer sees almost the exact image that is recorded on the film. The photographer can adjust the focus, select the shutter speed, and control the opening of the diaphragm.
Many new models can also adjust the focus and control the light exposure automatically.
These lenses include wide-angle lenses, telephoto lenses, and zoom lenses. A wide-angle lens provides a wider view of a scene than a standard lens does. A telephoto lens makes objects appear closer. A zoom lens combines features of standard, wide-angle, and telephoto lenses. The image in the viewfinder appears on a flat screen built into the top of the camera.