The eyepiece on a camera that allows the photographer to compose and determine the focus of the image received through the lens. An optical viewfinder, used in single-lens reflex (SLR) cameras, contains a mirror and a pentaprism, which together reflect the light entering the camera as an optically accurate image. Digital mirrorless cameras feature electronic viewfinders which do not optically reflect the image; instead, they are tiny screens that show the image as recorded by the camera’s sensor, with settings such as white balance and colour adjustment already in effect.