There are two important properties in penta-prisms. The first one is that the image is neither inverted nor reversed as it is deviated by 90 degrees. Secondly, the penta-prism is a constant deviation prism, meaning that the same exact 90-degree deviation applies to all rays transmitted by the useful aperture,regardless of the angles between these rays and the optical axis. They are often used in range finding, surveying, alignment and cinephotography.