The Mamiya Variable Diopter Flip-Up Magnifier for Prism Finders assures enhanced precision focusing by magnifying the central portion of the screen 2 times. Note: For 1000S, 645 & 645J, as well as Pro & Super; This magnifier only enhances the central part of the focusing screen; For AE Prism Finder & standard Prism Finder Provides a twice normal (2X) magnification of the central area; Particularly useful for critical focusing with wide angle, telephoto & variable soft focus lenses, as well as for copy work & macro photography It is attached by merely sliding it on to the camera's viewfinder; After focusing, flip it up for normal viewing Diopter adjustment is also possible with a range from -5 to +5 to accommodate near or farsighted vision 5 lens elements in 2 groups it produces an unreversed & laterally correct image