Leica/Leitz Imarect 35-135 Finder

All early Leica screw-mount view finder was calbrated for 50mm standard lens, therefore, if you use a wide angle or telephoto lens, you would need a Imarect or Vidom finders that shows the field of view from 35mm to 135mm!  Note.  The above Leica IIIf with self-timer is mounted with a 90/f4.0 Elmar lens and the Imarect!