Exposure Control
An appropriate exposure for a photograph is determined by the sensitivity of the medium used. For photographic film, sensitivity is referred to as film speed and is measured on a scale published by the International Organization for Standardization (ISO). Faster film, that is, film with a higher ISO rating, requires less exposure to make a good image. Digital cameras usually have variable ISO settings that provide additional flexibility. Exposure is a combination of the length of time and the illuminance at the photosensitive material. Exposure time is controlled in a camera by shutter speed and the illuminance by the lens aperture and the scene luminance. Slower shutter speeds (exposing the medium for a longer period of time), and greater lens apertures (admitting more light), and higher-luminance scenes produce greater exposures.
An approximately correct exposure will be obtained on a sunny day using ISO 100 film, an aperture of f/16 and a shutter speed of 1/100 of a second. This is called the sunny 16 rule: at an aperture of f/16 on a sunny day, a suitable shutter speed will be one over the film speed (or closest equivalent).
A scene can be exposed in many ways, depending on the desired effect a photographer wishes to convey.
Read more about this topic: Exposure (photography)
Famous quotes containing the word control:
“Why wont they let a year die without bringing in a new one on the instant, cant they use birth control on time? I want an interregnum. The stupid years patter on with unrelenting feet, never stopping—rising to little monotonous peaks in our imaginations at festivals like New Year’s and Easter and Christmas—But, goodness, why need they do it?”
—John Dos Passos (1896–1970)