Copal 3 equivalent with round diaphragm

[Larry Gebhardt]

I've got a 210mm Macro Sironar N which is in a Copal 3 shutter. Given that it's a macro lens I frequently have significant areas of the photo out of focus. If there are highlights in the out of focus area they are rendered in the shape of the aperture, which I find unappealing. I'm wondering if there's an easy shutter replacement that would have a round diaphragm. Ideally it will be a shutter, but I guess a barrel would also be a workable solution in many of my shots.

[Oren Grad]

One of my lenses is in a very early Copal 3 with a non-linear aperture scale and a ten-bladed iris instead of the seven-bladed iris that you see in later Copal 3's. Still a polygon, but subjectively a lot closer to round through much of its adjustment range. Perhaps it would be a direct swap, too.

[Richard Johnson]

Otherwise I doubt there is a solution other than using the lens wide open or making and rigging custom Waterhouse-style stops. Or using an old Acme or Ilex.

[Phil Hudson]

You might get a rounder aperture from a Compur 3.....

[Larry Gebhardt]

Looking at some pictures of the older Copal 3 the diaphragm does look closer to round. Probably would be close enough for my taste. The only Compur 3 shutter I see on ebay looks like what I had in mind. I'll keep an eye out for a bargain on one.

[domaz]

You could have the lens remounted into a Compound, but that would be very expensive.

[EdSawyer]

Compound or compur 3 both have more blades. Compound > compur > copal > Prontor (5! and straight!)

[Larry Gebhardt]

The compound looks perfect. I never knew these existed until now.

[koh303]

I had and sold a telexenar in a compound size 3, with a zillion blades, and a near circular opening.
Was a pretty thing. Those lenses are not expensive if you can find them, and the shutters are not that bad (though not great either).

[domaz]

I had and sold a telexenar in a compound size 3, with a zillion blades, and a near circular opening.
Was a pretty thing. Those lenses are not expensive if you can find them, and the shutters are not that bad (though not great either).

Compounds are reliable although I have my doubts that their air cylinder mechanism will be accurate when I'm high up in the mountains. Maybe not a good shutter for people living in Denver.