Quote Originally Posted by Jim Graves View Post
Kevin ... if you're asking about the 14" CE in the Ilex No. 5 Universal ... my aperture measures at 52mm when set @ f-6.3 ... as does OP's ... but it opens to 57mm when moved beyond the f-6.3 setting to the end of it's range.

Interesting thing is ... if you divide 14" by 57mm you get 6.3 ?!?!?! But, of course, optics are not that simple ... with nodal points, etc., etc., etc. More thinking than I want to do ... I just put the pointer on 6.3, set the meter for 6.3, and forget about the caliper measurements. I'm just going to assume they knew what they were doing when they made the lens. As for OP's friend and his barrel lens ... I have no idea what happened.
Try this, measure with your calipers the iris opening with the glass on, then off. You will have different measurements.