aperture ring

An aperture ring is a control found on some camera lenses that allows you to manually adjust the size of the lens opening, called the aperture. The aperture controls how much light enters the camera and reaches the sensor or film. By rotating the ring, you select different f-stop settings, which impact the exposure and depth of field—how much of the image is in sharp focus. Smaller openings (larger f-stop numbers) let in less light and create a deeper focus, while larger openings (smaller f-stop numbers) let in more light and produce a shallower focus.