A popular lens in the user market, many photogs consider the DR their sharpest lens. A 50 DR had the honor of having the highest resolution ever tested by the now sorely missed American photography magazine, Modern Photography, at over 100 lines per mm. Using it in the close up range can be confusing, and so the detailed explanation below. The eyes must be removed before mounting or dismounting the lens. The eyes will not mount in normal focusing range because the interlocking dovetail mount ball bearing can only be depressed in the close focusing range.
Right pic shows close-up of the eyes dovetail mount with the ball bearing.
The pics don't adequately show the magnificent fit and finish of the Dual Range. Until you hold them side by side in your hands, you won't fully appreciate the construction differences of the classic 50's and 60's lenses compared to modern lenses. For Visoflex fans, the focusing head of the DR will unscrew for bellows close up work. While the DR will mount on the Leica CL, Minolta CLE, the closeup attachment will not line up properly to these camera's viewfinders in the close focusing range. I have not tried the DR on a Konica RF, but suspect it would work fine, even in the close focusing range.