The Leica Correction Lenses offer the most favorable eye to camera matching that even photographers having slight eyesight deficiencies can focus accurately. These Diopter Correction Lenses enables you to comfortably compose images in the viewfinder. It offers better and comfortable focusing than when done with the eyeglasses.The Leica Correction Lens is obtainable in plus/minus 0.5, 1, 1.5, 2 and 3 grade dioptersThe viewfinder of Leica M comes can be preset by default to -0.5 diopters that if you wear 1 diopter strength glasses, you would need a +1.5 diopter Leica Correction Lens