Introduction Exposure is the amount of light required to correctly expose an image. Exposure is a combination of intensity (the quantity of light determined by the size of the aperture) and duration (the quantity of light determined by the length of the shutter speed). Correct exposure is the interpretation of light meter measurements related to the desired effect and the subject being photographed. Too much light will result in overexposure. Too little light will result in underexposure. It makes no difference whether there is a large or a small amount of light, the same amount of light is still required for correct exposure. Exposure has to be adjusted to compensate for these variations. This is achieved by adjusting either the intensity (aperture) or duration of light (time). An increase in the size of the aperture will give more exposure, a decrease will give less exposure. A decrease in the duration of the shutter speed will reduce exposure, an increase will give more exposure.