The Leica Correction Lens provides perfect eye-to-camera matching and enables accurate focusing to photographers. The Leica M Diopter +0.5 lens with the combined rangefinder/viewfinder options allows even photographers with minor eye deficiencies to focus perfectly.You can compose images in the viewfinder easily with this diopter correction lensThe Leica Correction Lens is available in varied grades of plus/minus 0.5, 1, 1.5, 2, and 3 dioptersThe viewfinder of the Leica M is preset to -0.5 diopter by defaultIf you wear glasses of 1 diopter strength, then you will need a +1.5 Leica diopter correction lens