Normally, a long focal length of 800 mm also has an overall length of nearly 80 cm to the sensor plane. To achieve a handy, versatile, and compact solution, this lens employs a clever trick. The light path is simply folded using two high-precision ground mirrors. This results in a compact design of only 131 mm in length compared to the nearly 80 cm mentioned. The minimum focusing distance is also reduced to 3.5 meters instead of at least 10 m with a lens-based system. Focusing is done manually. Depending on the camera, the lens can be used with automatic exposure or manual exposure settings. In the folded light path, it is technically not possible to incorporate an iris diaphragm. If light reduction is necessary, this is simply achieved through 2x or 4x neutral density filters, which are screwed in front of the rear lens. There is a thread M30x0.5 available for this purpose. Practically, the lens does not have a fixed defined infinity stop. Fine focusing is performed by swinging, allowing the focus point to be confidently found from out of focus to sharp and back to out of focus at any distance.