Rollei RPX-D is a developer for all b&w film, but has been optimized for use with Rollei RPX 400 to achieve full film speed. Rollei RPX-D offers high quality results when pushing (underexposing), expanding the effective speed from 400 up to 3,200 ASA. Even in the range from 800 up to 1600 ASA there are no changes of the tonal value visible. From 3,200 ASA and more, the grain increases but the tonal value does not decrease visibly. For a high-speed film, Rollei RPX-D offers an exceptional degree of edge sharpness.