This lens with magnifier spectacles, that enlarge the finder view by 1.4 and allows the 90mm frame to be used for the 135mm perspective, indicates the limits of the rangefinder accuracy and also the efforts Leitz was willing to take to expand the possibilities of the M-system. It is true that the rangfinder mechnism in itself has the required precision (especially when using the vernier acuity method: the aligment of vertical lines at the vertical edge of the rangefinder spot). But the sensitivity of the eye may not be good enough in some instances. To add a safety margin, this magnifier arrangement works, but the whole assembly is quite cumbersome. The weight is such that tripod mounted operation would be required in many situation.