People nowadays are very familiar with SLR cameras. SLR cameras are single-lens reflex viewfinder digital cameras. The principle of SLR cameras is to use a single lens to view the view, and the light shines on the mirror through the lens. Why do SLR cameras use a penta prism?
The imaging principle of the SLR camera is the small hole imaging. We know that the small hole is imaged upside down. Therefore, the SLR camera is because the scene passes through the lens and the image formed on the photosensitive element is upside down, so a penta prism is used to process the image formed through the lens, the human eye can finally observe the subject in the camera's viewfinder. This viewfinder method is called an optical viewfinder, and a single-lens reflex camera is an optical viewfinder camera.
The internal structure of the SLR has a mirror and a penta prism for various reflections of light. These mirrors and penta prisms used to physically reflect external light to the viewfinder become the main components of the SLR camera's viewfinder. It is also the most special place for SLR cameras. The pentaprism is a reflection device for the viewfinder of a single-lens reflex camera. Its function is to correct the upside-down image on the focusing screen, so that the image seen in the viewfinder is completely consistent with the orientation of the scenery directly seen, so that the operator can correctly view and focus. When the shutter is open, the reflector flips upward to give way to the light path, and no light is transmitted through the penta prism.