Diaphragm

        A diaphragm is a thin opaque structure with an opening or aperture at its center. The role of the diaphragm is to stop the the passage of light, except for the light passing through the aperture. This is why it is also referred to as a stop (an aperture stop) because it limits the brightness of light that reaches the focal plane. The diaphragm is placed in the light path of a lens or objective and the size of the aperture regulates the amount of light that passes through the lens. Most modern cameras use a type of diaphragm called an iris diaphragm. In a film camera the aperture is the whole in the lens that opens or closes to let more or less light into the camera to expose the film. The aperture settings work with shutter speed to determine length of film exposure. The aperture settings of a film camera (no matter the format), are known as f-stops. The lower the f-stop number, the larger the hole in the lens becomes allowing more light in. Also the higher the f-stop number, the smaller the hole in the lens becomes allowing less light in.

By: erinn