DIY iris fix for using Canon FD lenses on 35mm adapters:
 

Not sure if someone has already come up with this, but I thought I'd share:

I discovered that most Canon FD type lenses will not let you adjust the iris when mounted to a LetusXL or presumably any other 35mm adapter with a Canon FD mount. So after studying the issue for a bit, I came up with a way that solves the problem.

I devised a sort of simple shim using a trimmed down Q-Tip shaft and placed that between a hard point on the back of the lens and the iris actuator. To hold the shim in place, I placed a small amount of hot glue to one side. I chose hot glue over super glue or Elmer's glue because it won't seep into the lens, is somewhat malleable, and is not a permanent adhesive, meaning I can take the shim fix off the lens without damaging it or leaving any residue.

I have included a couple pics to show the shim fix on a Canon FD 50mm F1.4 lens. The first is the lens alone with the shim fix at wide open and the second pic is the lens with the LetusXL Canon FD adapter attached and stopped down to about F16. All in all, a pretty easy and cheap DIY fix.