What is the adjustable opening in a camera that controls the amount of light?

The adjustable opening in a camera that controls the amount of light is known as the aperture. The aperture is a crucial part of a camera's lens system that can be opened or closed to allow varying amounts of light to reach the camera's sensor or film. By adjusting the aperture, photographers can control not only the exposure of the image but also the depth of field, which influences how much of the scene appears in focus.

Aperture is measured in f-stops (like f/2.8, f/4, f/5.6, etc.), where a lower f-stop allows more light to enter (wider opening) and a higher f-stop allows less light (narrower opening). This adjustment is essential for achieving the desired artistic effect and exposure, making it a fundamental concept in photography.