Large (and maybe medium) format shutter threading

fdonadio

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Hello, everybody!


I have a Copal and a Seiko shutter, both in size #0 and, to a certain point, several lenses can be used interchangeably in both, since their length is the same (at least according to specs). I can find the overall length of the lens and use washers to make it the same on every shutter, measuring with a calliper.

But then I had an Ilex Super Paragon modified to fit the Seiko, which I'm now trying to use on a Copal and something came up: there are small differences! Look at the photos below:


(Seiko on the Ieft, Copal on the right.)

In the back of the Seiko, the thread goes pretty much to the edge, while on the Copal, there's a gap with no threads, around 1.5 mm long. Since the Super Paragon's back cell has an element that protrudes into the shutter, I can't fit it in the Copal without it touching the iris (aperture) blades. The "extra" threading on the Seiko allows for 3 turns of the back cell, which is good enough to keep it firmly in place. Both shutters have a gap on the front thread, but then again the Seiko has a smaller one, although this is not a problem with this particular lens.

Now I need to replace this shutter, since it's not working very well and can't be serviced here in Brazil due to lack of parts. But I need to know: are these gaps standard on every Copal shutter? What about Prontor, Compur and other brands?

Yes, I know this problem can be avoided by by replacing it with an identical Seiko shutter, but these are not very easy to find (even on evilBay). Copals are everywhere, often cheaper and easier to service.

Could anyone here have good news for me?


Regards,
Flavio
 

Dan Fromm

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Flavio, is your Copal a cock-and-shoot or a press (self-cocking) shutter?

I ask because although both types have the same tube length press shutters have slightly shorter rear and slightly longer front tubes than cock-and-shoots. The shorter rear tube can allow the inner (diaphragm-facing) element of rear cells that go deep into the shutter to contact the diaphragm.

You need more than cells that are firmly in place. You need cells that are the right distance apart. So measure rear of rear tube-to-diaphragm distances for both of your shutters.
 
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fdonadio

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Dan Fromm said:
Flavio, is your Copal a cock-and-shoot or a press (self-cocking) shutter?
Click to expand...

Thanks for the input, Dan!

It’s not a press one. It’s a cock-and-shoot. Tube is 20mm long, not 16mm, as with the press ones.

I measured the distance from the back of the tube to the iris mechanism and there’s a ~0.3mm difference between the Seiko and the Copal. The Seiko is “shallower”.

I know how to set the cells to the correct distance by using “washers” and spacers. I have the original barrel that the lens came in, so I can measure the length of the whole assembly and use that measurement to mount the cells on the shutter.
 

Dan Fromm

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Flavio, all #0 and #1 shutters, press and cock-and-shoot, have 20 mm tube length. That's the standard. #00 shutters have 16 mm tubes. Believe me, I have #0 and #1 press and cock-and-shoot shutters, also #00s.

Anyway, good luck.

#00 shutter story to amuse you. Years ago I bought a 47/8 mystery lens in a tiny Ilex electronic shutter. The shutter's tubes were threaded like #00 but the shutter (Ilex, remember, shutter makers in Rochester didn't follow the Compur standard) had a shorter tube than a Compur #00. So the lens' cells didn't go deep enough into a Compur #00 to give good image quality. I sent the lens in its Ilex shutter and a Compur #00 to Steve Grimes. He muttered "the shoulder problem" and machined the #00 lightly so that the cells would go deep enough in it.
 
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fdonadio

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Dan Fromm said:
Flavio, all #0 and #1 shutters, press and cock-and-shoot, have 20 mm tube length. That's the standard. #00 shutters have 16 mm tubes.
Click to expand...

Yes, you’re right. My bad.

I’ve searched Google like crazy the last two days, have read a lot of documents on shutter specs. Not a single word about the thread gap I asked on this thread.

Maybe the only way is using Seiko shutters for this lens.

I even thought about further modifying this lens to fit a smaller shutter, since it’s a 38 mm f/4.5. The maximum aperture size will be around 9.44 mm. Even a #000 would do, but these are even harder to find. And smaller shutters will get the protruding element issue even worse!
 

Dan Fromm

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Oh. That Super Paragon. It is a Biogon, as was fitted to Hasselblad Super Wide and successors.

I vaguely recall that we discussed this lens. I think. Did you buy it from Westlicht?

Your best bet may be to have threaded bushings that will let you mount it in a #1.
 
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fdonadio

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I don’t remember who I talked to about it. Somebody here on Photrio recommended me this lens and I bought it for my “Poor Man’s SWC” project, which I still have to finish... Yes, it’s a Biogon!

I got it from a Fairchild aerial camera I bought from Leica Store Vienna for not much, back in January 2019.

The idea of getting it into a larger shutter is not a bad one. It would be an easier adaptation. But since I had the cells machined for a #0 shutter, it makes sense to keep it that way.

Let’s check shutterfinger’s Prontor S...
 
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fdonadio

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shutterfinger said:
I have a good working #0 Prontor S for the price of a US CLA.
Click to expand...

Thanks for the offer. From what I gather, the Prontor S was used in folders and had those older speeds (1, 2, 5, 10, 20, 50, 100 and 250)... I would prefer a more modern set of speeds and the 500 would also be very desirable.
 

Dan Fromm

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You discussed it with me. Leica Store Vienna is Westlicht on eBay. The camera and lens you bought used to belong to my neighbor Charlie Barringer.

Please post a side view of the rear cell. I ask because I've looked into the rears of two Copal #0s -- cock-and-shoot and press -- and one Seiko #0. Your shutters are perfectly normal. I also measured the Seiko's and Copal cock-and-shoot's rear tube lengths. The Seiko's is 0.3 mm longer. Please measure both of your shutters to confirm this.

If I got it right, using threaded bushings to put the cells in a Copal #1 won't work. But and however I'm not a skilled machinist, so take both shutters and the cells to the machinist who did the cells for you and ask him what he can do, making it very clear that cell spacing (= lens' total length) is critical.

If he can't make things right, look for a bad Fujinon lens in a good #0 Seiko. They're fairly common on ebay.com, more common on yahoo.jp. I go to yahoo.jp via buyee.jp, which uses google translate.
 
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fdonadio

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Dan Fromm said:
You discussed it with me. Leica Store Vienna is Westlicht on eBay. The camera and lens you bought used to belong to my neighbor Charlie Barringer.
Click to expand...

Yes, I searched my personal messages and saw that we talked on the beginning of 2019, right after I got back from Italy. Wow, what a coincidence this lens belonged to your neighbour! That's nice to hear...

Please post a side view of the rear cell.
Click to expand...

Here it is:


You can see the machinist has cut a thread (the "silver" one) to fit it into the shutter's tube. The same was made with the front cell. Not a "beautiful" job when you compare the quality of the threads to the original ones, but this machinist does a lot of lens conversions and adaptations for cinema photographers here in Brazil and must know what he's doing. Since the cells screw easily and firmly into the shutter, it's OK with me.

The Seiko's is 0.3 mm longer. Please measure both of your shutters to confirm this.
Click to expand...

Again, you're right. I should have said "the Seiko is deeper". The Seiko's back tube is 8.65mm long and the Copal is 8.30mm long. A 0.35 mm difference. The 0.05 is debatable, though, as the quality of my calliper and my measurement skills may not be very good.

If I got it right, using threaded bushings to put the cells in a Copal #1 won't work. (...) If he (the machinist) can't make things right, look for a bad Fujinon lens in a good #0 Seiko.
Click to expand...

I think it's better to avoid having these cells machined again and the safest way is using another Seiko just like it. Or make sure the replacement shutter's back tube is deep enough and the threads go to the the edge of it. @shutterfinger's Prontor is a good candidate.

Thanks for all the help, Dan.
 
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fdonadio

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shutterfinger said:
The Prontor is 6.89mm to the surface of the aperture blades. The rear threads are 5.9mm deep from the edge of the tube.
Click to expand...

Thank you very much, shutterfinger! This measurement confirms that press shutters have the iris and shutter mechanisms further to the back, compared to non-press shutters, making the back tube shorter.

From the pictures I have seen on Google, the Seiko seems to be the only shutter with threads like I need. Crazy, eh?
 
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