Which component of a lens determines how much light is allowed to enter?

The component of a lens that determines how much light is allowed to enter is the aperture. The aperture is an opening in the lens that can be adjusted to control the amount of light that passes through and reaches the camera sensor or film. A wider aperture (indicated by a lower f-stop number) allows more light in, while a narrower aperture (higher f-stop number) reduces the light intake. This control over light is crucial for achieving proper exposure in photography and videography, allowing creators to manipulate depth of field as well.

Other components, such as the shutter, are responsible for controlling the duration of time the light hits the sensor, while filters can alter the characteristics of light entering the lens but do not directly control the amount of light. The zoom ring affects the focal length and magnification of the image but also does not influence the light quantity entering the lens.