The Single Lens Reflex Camera is called a SLR Camera. It refers to a camera that USES a single lens and USES it to reflect light.The so-called "single lens" means that the photographic exposure path and the viewfinder path share the same lens, and there is no independent lens in the viewfinder path. "Reflection" refers to a planar mirror in the camera to separate the two light paths. When shooting, the mirror is quickly lifted and the light can be shone on the film or sensor CMOS or CCD.In this system, the unique design of the mirror and prism enables the photographer to directly observe the image through the lens from the viewfinder.