Are Compur 3 and Copal 3 interchangeable?

[Amfooty]

Sorry if this is a stupid question--I have searched around but haven't been able to find a straight answer. I have a 240mm Symmar in a Compur Electro #3 that decided it is too good to change shutter speeds. It looks like there are some old version copal 3's available in the form of Fuji SF lenses. Would the lens spacing be the same between Compur and Copal?

[Dan Fromm]

The question is whether the tube lengths are the same. Measure your Compur, then compare with http://www.skgrimes.com/products/new-copal-shutters/standardcopals for overall thickness. Or visit http://www.suaudeau.eu/memo/pratique/Les_obturateurs_centraux.html

I think you'll find that your shutter (measure it!) matches a Copal #3s but I could be mistaken.

[Tin Can]

How close does that measurement need to be?

To what level of precision, as it may be difficult to obtain accuracy with a dial caliper, using it as depth gauge.

[Dan Fromm]

Randy, shame on you. If you'd followed the suadeau or (you couldn't but now it is right) skgrimes links you'd have learned that the 3 is ~ 3 mm longer than the 3s. Low precision should be good enough. My cheap calipers can measure an Ilex 3's thickness to much closer than 3 mm, ought to be able to do the same for a Copal 3. Tube length, end-to-end, is what matters.

[Tin Can]

I am shamed.

[Amfooty]

Well good news is that the Compur Electro 3 and Copal 3 match. That should make this whole thing a lot easier on my wallet. Thanks for the links--I really appreciate it.

[Peter Yeti]

You mention that the Compur electronic 3 doesn't want to change shutter speed. Couldn't this simply be a weak or dead battery? Without battery it always releases at full speed.

Peter

[Amfooty]

You mention that the Compur electronic 3 doesn't want to change shutter speed. Couldn't this simply be a weak or dead battery? Without battery it always releases at full speed.

Peter

Even with a fresh battery the shutter speed dial won't turn.

[Peter Yeti]

OK, if the rim dial to set the shutter speed doesn't move, this might be a simple mechanical problem, e.g. dirt or corrosion. If it's only the rim, it might be easy to fix by cleaning. Of course there is a chance that the actual shutter mechanism is affected as well. In any case, it might be worth trying to make it work again before investing big bucks into a replacement shutter.

Peter

[Old-N-Feeble]

Well good news is that the Compur Electro 3 and Copal 3 match. That should make this whole thing a lot easier on my wallet. Thanks for the links--I really appreciate it.

Be aware that some Copal 3S shutters are marked "Copal 3", not always marked "3S".

[Alan Gales]

Be aware that some Copal 3S shutters are marked "Copal 3", not always marked "3S".

Yeah, What's up with that?

[Luis-F-S]

How about between a regular Compur 3 and a Copal 3? I have some 240 Sironar N cells that came off a Compur 3 shutter and was wondering if they'll screw directly into a Copal 3? Anyone have any experience with this? Don't own a dial caliper. L

[Old-N-Feeble]

Yeah, What's up with that?

I can only guess an oversight by Copal.

[Jim Galli]

I can only guess an oversight by Copal.

No oversight. When Copal first got into this business in a big way they were replacing the long time champion at Schneider which was the Compound no. 3. Thus they started with a Copal 3 that had the same 56mm thread and spacing as the venerable compound. Later on things settled out and the 58mm thread became standard as well as the spacing. So for the OP's original intent, a later black copal would work fine. Everything was sort of standardized by then. Make sure you get the correct matching mounting nut as those are all over the place with Copal 3's. That said, I've found the Compur 3 Electronic to be amazingly simple and stable little machines with timing far better than mechanical shutters. Find a watch repairman who can investigate for you. No parts are available though. So if the little fingers that rub the slip ring inside that tells it where the speed selector is set are boogered, it probably is dead.

[domaz]

Even with a fresh battery the shutter speed dial won't turn.

That sounds bad. The shutter speed dial on Compur electronics just basically turn a contact over a series of resistor contacts, no real mechanical interfaces there. If the dial won't turn it's either something simple like the shutter front face retaining ring (visible on the front side of the shutter with the front element removed) is way too tight- or something else like rusted contacts.

[Amfooty]

That sounds bad. The shutter speed dial on Compur electronics just basically turn a contact over a series of resistor contacts, no real mechanical interfaces there. If the dial won't turn it's either something simple like the shutter front face retaining ring (visible on the front side of the shutter with the front element removed) is way too tight- or something else like rusted contacts.

Well I'll be. The retaining ring was too tight. Must have done that by mistake when screwing it on the lens board. How important is that collar? If the front element of the lens is screwed in all the way like my other lf lenses, the dial won't turn. It will only turn when slightly unscrewed.

[carverlux]

Well I'll be. The retaining ring was too tight. Must have done that by mistake when screwing it on the lens board. How important is that collar? If the front element of the lens is screwed in all the way like my other lf lenses, the dial won't turn. It will only turn when slightly unscrewed.

My experience with Copal 3, Coimpur 3 and Compur 3 Electronic is that they are not "plug-compatible". The Copal 3 has more generous (meaning deeper and slightly wider) lens cavities for cells to fit into, and the spacing between the front and back is not the same as the Compur's - which are much closer but there is enough variation between the ones I own that I would not treat them as interchangeable.

This came to light when I was working with SK Grimes to develop a "universal" #3 shutter based on the much more versatile Compur 3 Electronic, the idea being to carry one shutter with many lens cells for a lighter traveling pack. Adam called me after he started and told me that they are pretty different, and that's why they never made generic lens cell adapters, but fit each shutter to a specific lens. I measured a few I had on hand and sure enough, some just downright would not fit. In the end, a "universal" #3 that would take both Compur and Copal was not to be, and I now stick with the shutter the lens was mounted on originally, or use the Sinar Shutter.

Therefore when I read the part in your post where you had "screwed the front element in all the way", I just cringed - you could be grinding that glass against the shutter if it was a Copal cell being screwed into a Compur! My suggestion is bite the bullet and get it done by the pro's. The Compur Electronic shutters remain my favorite.

carver

[Amfooty]

Therefore when I read the part in your post where you had "screwed the front element in all the way", I just cringed - you could be grinding that glass against the shutter if it was a Copal cell being screwed into a Compur! My suggestion is bite the bullet and get it done by the pro's. The Compur Electronic shutters remain my favorite.

carver

Just checked, and both the shutter and the front element are safe. Nearly positive the lens shipped with the Compur Shutter, so there isn't an issue there. I made the simple mistake of not threading in the collar as far as it could go before adding the front element. Everything is good with the lens now. Spent too much time in the darkroom today and wasn't really thinking the collar aspect through.