ABSTRACT
The photographic exposure refers to the quantity of light received in a unit area of photographic film or paper, calculated by multiplying the illuminance of the light falling on a small area of the film or paper by the exposure time. The factor that determines photographic exposure in addition to image illuminance is exposure time. With exposure time, view camera lenses is controlled by a shutter located within or close to the lens, identified as a between-the-lens shutter or lens shutter—as distinct from focal planeshutters, which are located in front of and close to the film. In a typical picture-taking situation, the film receives many different photographic exposures in different areas corresponding to variations in lightness of different parts of the scene being photographed. Opening the diaphragm by one stop doubles all the different illuminances that constitute the light image on the film. The problem of variations in the transmittance of lenses increases with the number of elements.
