Penta Prisms
¨Neither inverting nor reverse imaging 
¨Constant 90°deviation

The penta Prism is a five-sided prism, featuring two important properties. First, the image is neither inverted nor reversed while it is deviated by 90°. Secondly, it is a constant deflection device,i.e. all the transmitted rays are deviated by the same exact 90 degrees. Slight movement of the prisms does not affect the true right angle. This feature makes the prism useful in range-finders. It is also used in viewfinders of single reflex cameras. The reflecting surfaces are enhanced aluminum coated with black paint overcoat for protection.