Canon S 50/1.2 LTM

Lightshow · Joined: 04 Nov 2011 Posts: 3669 Location: Calgary

An issue I've had with my Canon RF 50/1.2 lens is that the aperture ring didn't move the full range 1.2-22, it went from 22 to 2, but seemed to not want to move any further.

Fast forward to today, I opened it up to see what's causing it, nothing obvious...

The aperture is made up of a backing disk with holes that the blades sit into, and a drum with angled slots that the aperture ring turns to move the blades in a synchronous fashion.

I unscrewed the grub/set screw that locks the aperture backing disk in place, it is used to set the aperture to a calibrated position, I assumed that this was set wrong, with it loose, turning the aperture ring to both ends causes the aperture to open and close, but at the ends, it moves the backing disk the last bit...
So it seems like the drum was designed for a shorter range of movement.... which puzzles me.

Edit: Turns out that the last person to service the aperture blade, backing disk, and drum, assembled it wrong, the drum was clocked wrong.

Now all I have to do is get it back together with all 11 blades in the right spot....

Edit again: All back together, and works as it should. Smile

tomasg · Expire: 2014-04-28

Congrats, it s one of the most difficult things to fix a lens after it was messed up by someone else!