This Mamiya Focusing Screen Type "C" Microprism Spot is optimized for critical manual focusing. It has a central microprism focusing collar which will help those who have difficulty focusing with a plain matte screen. This screen is still calibrated for the camera's metering system.
Mamiya offers three interchangeable screens for the 645AFD camera
Checker SD 402 - Same as Matte, but with perpendicular grid. The grid pattern is ideal as a compositional aid. Grid intersections also useful as reference points for multiple exposures
Matte SA402 - All matte with Fresnel lens, suited for general-purpose photography
Microprism Type C - for Non-AF 645 Lenses - Same as Matte, but with central microprism spot added. Provides an alternative Rangefinder Spot screen for enhanced focusing precision with the manual focus lenses. When using the manual focus lenses in the stop down metering mode, this screen must be used