The diaphragm of a lens is an opening in the lens that allows light to pass through it to expose the film (or other recording medium). This opening can be made larger or smaller to allow more or less light to pass through the lens. When the diaphragm opening is very

Figure 1-22. Angle of view.

large, only the object that the lens is focused on is in sharp focus. As the diaphragm opening is reduced (made smaller), more objects in a scene, both in front and behind the point of focus become sharper. The lens diaphragm is used in conjunction with the shutter of the camera to control the amount of light to expose the film.