Unjamming an RR/symmetrical f8 lens...

While rummaging around at the back of a cupboard at home I came across a 'Beck Symmetrical f8' lens - from what I have read it is an RR type design. Anyway, the aperture appears to be jammed at nearly wide open. I can easily unscrew the front group of elements and the aperture seems to have become eccentric in its shape - how do you correct this? Also the lens seems to be attached to a short, threaded bakelite(?) mount - any ideas as to what this lens could have been used for? My Grandad has no idea where the lens came from despite it being among his cameras. Focal length is at this stage unknown but the optics could also do with a good clean despite the brass being in good condition.

All help much appreciated,

Lachlan

Lachlan,

What you describe means that one or more of the blades have jumped out of position, possibly broken off their end pins. It would take a complete dismantle to clean and examine the parts. There are just too many styles of putting an aperture assembly into a barrel to give any worthwhile advice except to take it to a camera tech and have it checked.

Good luck with it.