sentence: Some cameras have an 'aperture ring'.
sentences_after: The aperture ring is behind the lens, but in front of the shutter. The purpose of the aperture ring is to control how much light enters the camera box. The aperture ring is a flat circle with a small hole in the centre. The small hole is called the 'aperture'. The size of the aperture can be changed.
concept_name: camera
headings: Photography Camera