Reflexspiegel

A reflexspiegel, or reflex mirror, is an optical component used in single-lens reflex cameras. It is a precisely positioned mirror at about a 45-degree angle that sits in the path of light coming through the lens. When viewed through the viewfinder, light is reflected by the reflexspiegel upward into a focusing screen and then through a pentaprism or pentamirror to the photographer’s eye. This arrangement allows the photographer to compose and focus the image using a view that shows exactly what the lens will capture.

During exposure, the reflexspiegel rapidly flips upward and out of the light path, blocking the viewfinder and allowing light to reach the image sensor or film behind the shutter. After the exposure, the mirror returns to its down position, restoring the view through the viewfinder. This mechanism, combined with a focal-plane shutter, is central to how traditional DSLRs and other SLR designs provide through-the-lens composition.

Reflex mirrors introduce mechanical complexity and a small amount of vibration, often referred to as mirror slap, and they cause a brief blackout of the viewfinder during exposure. They also contribute to the weight and size of the camera body. In recent years, many camera systems have moved toward mirrorless designs that omit the reflex mirror entirely, relying on electronic viewfinders or live image previews. Nevertheless, the reflexspiegel remains a defining element of classic SLR operation and image-forming accuracy.