What describes the hole in the iris of a lens?

• A. F-stop
• B. Shutter
• C. Aperture
• D. ISO

Answer: (C)

The hole in the iris of a lens is called the aperture. It’s the opening formed by the iris blades inside the lens and can be widened or narrowed to control how much light hits the sensor. The size of that opening is described by f-stops (f-numbers): a lower f-number means a larger opening and more light, which also gives a shallower depth of field; a higher f-number means a smaller opening and less light, with deeper depth of field. The shutter is a separate mechanism that determines how long the sensor is exposed, and ISO is the sensor’s sensitivity to light. So the hole itself is the aperture, the setting that describes its size is the f-stop, while shutter and ISO handle exposure duration and sensor sensitivity.