Genuine Leica Correction Lens II +3.0 Diopters for M10 If you are far-sighted and need to change the optics of the M10's 0.73x optical viewfinder, this Correction Lens II from Leica will provide a +3.0-dioptric adjustment. This will help shooters more comfortably use the camera, in some instances permitting use without the need for glasses.