f 1:1.2. Notice the light fall-off.

Details:

Center Notice the non circular star dots	Edge Typical coma wings

Regarding the non circular dots, they are caused by vignetting. The last lens element of the 1:1.2/50 is larger than 24mm, so the mirror house of the camera, not much larger than 24x36mm, blocks part of the last element at 1:1.2 !

schematic :

    mirror in up position
      |
      v            c
    __________     |
   a               |
 f |               |
 i |               |
 l |               |
 m |               |
   b               |
    ------C\--     |
                   d
          ^         last lens element 1:1.2/50
          |
          |
          `- LX light meter
 

light passing at position 'c' can't reach the film at 'a'
the same for 'd' and 'b'