Which component is defined as the element that controls the amount of light that reaches the film emulsion?

• A. Shutter
• B. Diaphragm
• C. Filter
• D. Viewfinder

Answer: (B)

Controlling the amount of light reaching the film emulsion is done by the diaphragm, the adjustable opening inside the lens (the aperture). When the diaphragm opens wider, more light passes through, brightening the exposure; when it closes down, less light gets through, darkening the exposure. The size of this opening is described by f-stops—lower f-numbers mean a larger opening and more light, higher f-numbers mean a smaller opening and less light. This component directly modulates light at the moment of exposure, whereas the shutter controls how long that light is allowed to hit the film (duration). A filter can reduce light as an accessory, but it’s not the primary exposure control, and the viewfinder is just for framing the shot.