a camera in
which the
image appears on a ground-glass viewer
(focusing screen) after being reflected by a mirror or after passing through a prism or semitransparent glass; in one type
(single-lens reflex camera), light passes through the same lens to both the ground glass and the film, while in another type
(twin-lens reflex camera), light passes through one lens
(viewing lens) to the ground glass and through a second lens
(taking lens) to the film, the lenses being mechanically coupled for focusing.
