Using Universal Iris Clamps

[Steven Tribe]

I didn't buy one - but it came on a camera!

Having played with it for some time have have some questions for others with much more experience than I have, I hope.

The edges of the leaves do not seem to fit in the "valleys" of the threads as I imagined.
It is slightly better with some of the "pipe thread" early threads.
Objectives don't actually fall out but they are never held very securely - they rock.
The only way I can see it would work is if it (the lens thread) was covered with some kind of tape that the iris could press into. Thinking about it in terms of mechanics and leverage, I would think that a dual clamping iris would be necessary to give stability.

The solution I have is to screw the retaining ring/flange right up to the blades from the back of the lens board. This was the method used on the camera when I bought it.

So the universal iris clamp seems to me to give a saving on lens boards, but not a solution for missing mounting flanges!

The one I have is without distorted leaves, as yet, and the locking mechanism works OK.

[eddie]

which kind do you have? the common german made ones?

i have not had this problem about not seating in the threads. what lenses are you using them on.

no, they are not as secure as one may think. i am careful not to move my cameras with a lens attached to the clamp. i also use a "safety" box for any expensive lens or any i worry about.

[Lachlan 717]

I have a large 240mm Petzval that I use by clamping it with an Iris. No flange, no tape.

It works fine. I just make sure that it is butted up against the blades.

Try a couple of test shots and see if you have any light leak.

[Steven Tribe]

I think it is standard German type with two identical rounded wing nuts. I discovered that flush idea was better but it was not secure enough to risk "front heavy" lenses. Petzvals, with their balance and protruding back seem better suited. I could live with light leaks, but not a fall from 4 feet. It certainly doesn't catch the threads in my small compound shutters.

[Lachlan 717]

Steve,

As I use this with a Sinar Shutter, I cannot pull the barrel back into the bellows area. Thus, the weight is all out the front. I haven't even had the slightest issue with securing the lens. I do, however, make sure that I lock the iris well once set (with the second nut).

I do understand your concerns; I've just never had the issue.

[eddie]

when in doubt go with the "chin strap" to help with the weight....

http://www.largeformatphotography.in...ght=chin+strap

[Robert Hughes]

Chin straps? Iris clamps? This is starting to sound like a BDSM site. What's next - shutter whips?

[goamules]

When I use a heavy, expensive petzval in my iris clamp I tie a string around the focus knob, and up around the top of the front standard. That way, if the iris lets the lens loose, it's only going to lean out a little, not fall to the ground. Just a safety strap....

[Steven Tribe]

I have done a refurbishment of my universal iris clamp (thanks to spare parts bought here) and must report that it now functions a lot better. It is still not really satisfactory with threads that approach the maximum aperture - up to about 3/4 open work well, though. This is logical, as the end thickness of the iris leaves "double up" when fully open.

[Raidahl]

Hi, I have one more question about these iris clamps, what is biggest iris clamp (max opening) that you have seen. I have one Meyer Görlitz Epidon 420/3.6 which do not have any flange to attach to eg. Sinar board and this kind of iris clamp could be solution. Or that day when I build my wet-plate camera, it would be nice to get that on front of it