How is aperture defined?

Aperture is defined as a hole or opening through which light travels. In the context of photography, the aperture refers specifically to the adjustable opening within a camera lens that controls the amount of light entering the camera. By varying the size of this opening, photographers can manipulate exposure and depth of field, affecting how the image appears in terms of brightness and detail sharpness in the foreground and background.

Understanding aperture is essential for achieving the desired artistic effect in photographs, as it not only influences exposure but also plays a crucial role in determining the visual characteristics of the images taken. Other options provided do not accurately define aperture; for instance, while a type of lens, distance to the subject, and sensitivity to light are all relevant concepts in photography, they each refer to different elements that interact with aperture rather than defining it.