I feel a bit silly asking this but I'm modeling a generic lens in a 3D modeling program simply to explain what an iris is. I'm just wondering where the iris is in the assembly of the lens? Right at the back? Or on the barrel where the actual adjustment is made?

Cal, it's near the back and in a fully manual iris, that's where you'll find the iris control ring because they are mechanically coupled.

Hope this helps.

-gb-

Thanks Greg, that was exactly the kind of answer I was looking for.