location of aperture in different shutters

[darinwc]

I have an odd lens that I am moving into a shutter.
It fits a copal 0 size thread.

one problem:
the rear element sinks so deeply into the shutter that is catches the aperture blades. It is a copal-press no. 0

Do any other shutters have a different placement of the aperture blades?
Prontor? Seiko? Compur?

Thanks

 

[Dave Parker]

I had the same problem with an Ilex No 4 shutter, the guy sold it to me because it would not stop down, I removed the cells and it worked fine, so I fashioned a very thin shim to go under the rear cell and it has worked great every since, no problems at all with the aperture blades hanging up.

R.

 

[Donald Qualls]

Beware of changing the original element spacing -- you'll introduce (at a minimum) spheric aberration (whether you notice or not depends on the lens). However, Darwin, that goes the other way, too -- the #0 shutter you're moving the lens into may be thinner than the shutter or barrel original to the lens; if so, a shim (effectively a very thin washer) under the shoulder of the rear element, sized to match the spacing of the original mount, would be the recommended correction. Otherwise, if you shim the rear, you really should take off the same amount from the front (though altering the shutter like that pretty much dedicates it to that one lens, which may not be desirable from a resale standpoint).

 

[dmax]

Do any other shutters have a different placement of the aperture blades?
Prontor? Seiko? Compur?
[/QUOTE]

I routinely transplant lens cells from different sources into shutters. As far as my experience goes, Compurs and Copal 0 (regular, not the Press type)shutters are equivalent when it comes to placement of aperture blades. In other words, lens cells from a Compur can go directly into a Copal 0 with no problems at all. Cell-to-cell spacing would be identical.

Seikosha shutters are a different matter altogether. Although Seikosha shutters will accept lens cells originally from a Compur or Copal 0, the placement of the diaphragm blades is different in the Seikosha. The rear lens cell from Seikosha, when transferred into a Copal 0, will jam against the aperture blades of the Copal 0 shutter. I ran into this problem when I was trying to transplant Mamiya lens cells (which come in Seikosha shutters) into Copal 0 or Synchro-Compur shutters.

I have not worked with Prontor (zero-sized) shutters, so I can't give you information on it. I have done quite a bit of work with older Prontor shutters(S and SVS) in zero-zero size, as well as similarly sized Compurs and Synchro-Compurs. Most are equivalents, but some are not!

 

[darinwc]

Thank Dmax. I have a seiko shutter that my SA is in right now. I can test it out and see if it works.

Otherwise, I think a shim might be in store for the lens.

 

[Harrigan]

Like Donald says just make sure you dont change the inner air space or the spacing distance btwn the front and real lens groups which is critical to the design of the lens. You must maintain the spacing withing a pretty tight tolerance or the lens performance will suffer. The degredation of the lens performace is dependent on the lens design and how much you actually modify the spacing. Some lenses degrade very badly with tiny changes while others may tolerate a bit more.

 

[darinwc]

UPDATE: I tried the cells in a newer Seiko shutter and they fit perfectly!
No problems with the apeture blades at all.

Now I will have to look for a dedicated replacement shutter.
Thanks for the help!