ISO on a camera stands for International Standards Organization, which is the governing body that sets sensitivity standards for sensors in digital cameras. ISO settings determine how sensitive the camera’s sensor is to light, while taking various types of photos.
ISO is roughly analogous to ASA film speed, in which the kind of film used had to have the right kind of light sensitivity in order to take good photos. The lower an ISO setting, the longer the exposure to gather enough light to capture an image. The higher the ISO, the more light the camera’s sensor gathers quickly, as in sports action shots and some types of news photos.
Each time a photographer doubles an ISO setting, the camera needs half as much light to capture the same exposure. Nikon lists the normal range for ISO settings in digital photography as 200 to 1600 ISO. Just as high-speed film caused grain in images, using higher ISO settings increase the amount of noise in digital images. Accordingly, the photographer’s job is to find the best compromise between ISO and shutter speed for a shot. As with film photography, digital photography combines ISO with shutter speed and lens f-stop to produce high-quality photographs.