Exposure

Exposure is the amount of light that passes through the lens and onto the CCD sensor. It is affected by aperture, shutter speed, Film/ISO speed, focal length of the lens and metering or how your camera measures light. Aperture and shutter speed are the two main ways that exposure is controlled. Aperture tells your camera how much light to let in and shutter speed tells your camera how long the lens should be open. The higher the aperture setting the more light that is let in and the slower the shutter speed the more light that is let in. By selecting certain modes for your camera, it can help you predict the amount of exposure needed for a particular shot. Camera's can also pick up on certain colors, such as white, which help it decide how much exposure is needed.

On my Canon PowerShot SX100, I have various modes to choose from which allows my camera to be helpful in many different ways. I can select aperture priorty or shutter speed priorty which which allow me to manually control each of this settings. There is also a manual mode which allows me to control both the aperture and shutter speed at the same time. If I feel lazy I can always choose one of the preset modes and hope that it decides to give me the correct exposure!