Single-lens reflex framing cameras are also known as SLR cameras. It is a camera that USES a single lens and reflects the view through this lens. A "single lens" means that the photographic exposure path and the framing path share a single lens, unlike a side-axis or dual-lens camera, which has a separate lens for framing. "Reflection" means that a flat reflector in the camera separates the two light paths: when the reflector falls, the lens light is reflected to the pentaprism, and then to the viewfinder window; When shooting, the mirror is raised rapidly and light can hit the sensor, CMOS or CCD.