Originally posted by Joseph3795 
The warning is certainly with regard to the 'rear element' which protrudes into the lens mount further then all the other 50mm F1.4 variants i.e. the 7 element versions.
That is the strange part. The warning is for ALL ST 50/1.4 and the reverse aperture direction 55/1.8. I agree that the issue is probably the more limited mirror box dimensions in the ES and ESII (SP F too) along with an aperture actuator that is quite different than on earlier Spotmatic models. Strangely, there is no warning for the SP F.
I have compared the rears of my reverse direction 55/1.8 with my later model and the early version inserts a little deeper and also has the actuator pin located slightly in-board of the later lens. My advice to owners of the 7-element ST 50/1.4 is that they evaluate fit visually from the rear (film door open) and shutter locked open in "B". Slowly rotate the lens into the mount (focus at MFD) taking care of any unusual feel or sound, particularly in the last rotation. Slowly move focus to infinity while monitoring the position of the rear element sheath relative to the bottom of the mirror box and the edge of the mirror (the mirror on all Spotmatics swings in a simple arc). If the actuator flipper stops down the lens, all is probably good, though I would take precaution to always confirm that the meter switch is in the down position (flipper disengaged) before removing the lens.
Steve
Post #9 by stevebrot
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