a camera in which
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.