Ever have a copal shutter problem like this?

[James Phillips]

I perhaps should say that this is not a problem with all Copal shutters to my knowledge but I was able to reproduce this problem on three of mine. It happened this way. I was out shooting about a week ago and had a light reading that required a shutter speed of ¼ second for my desired effect.

I was shooting an outdoor scene with my prime subject being a female friend. In all of the settings to consider such as light direction, background, posing and everything else I guess made me a bit casual about setting the shutter speed indicator. This is the first time this has happened to me and I was quite surprised to discover that this is normal.

What happened is that I had the indicator slightly off the click setting for ¼ and was exercising the shutter a few times while talking with my female model and attempting to put her at ease. When everything seemed good I began shooting Tri-X and everything seemed to have gone off without a hitch.

The next day in the darkroom I discovered that most of negatives were considerably under exposed to the point of being almost useless. I thought about the problem for a few minutes and concluded that the shutter was the culprit. I thought this strange as I use my Nikkor 300M often as I do with my Nikkor-W 210. The problem turned out to be that if the shutter is not set exactly at the indentation for ¼ then the shutter behaves more like 1/125 which obviously greatly under exposes the film. I proved this at home while playing with three of my Copal shutters. Just thought I might pass this along before somebody else as green as me gets bit by this.

Kind Regards,

[Jorge Gasteazoro]

You made me curious and I went and tried it. Darn it if you are not right! I did this with most of my copal shutters and they all exhibited this pecularity. What is even funnier is that it happens only at 1/4 of a sec. I tried the setting half way in the 1/2 and the 1/8 and above speeds and they all seemed to pick the next higher speed, but at 1/4 you are correct it went all the way to the top speed....strange!

[Alan Davenport]

At least some shutters use two different timing mechanisms. At the higher speeds, the timing mechanism connects directly through a gear train; as you vary the selected speed, the distance the release lever has to move is changed. At slow speeds, there is also added a delay (in the Alphax #4 it is a "fan" that uses air resistance to slow the gears.) At a guess, the "just off" setting you found is a point where the "delay" mechanism is not engaged... Now, that Alphax is the only LF shutter I've had apart, but I expect the mechanisms in others are probably similar.

[Doug Colton]

James: Strange but true, both my Copal shutters behave in exactly the same way. I have not been caught with underexposure because of the problem so far, and I appreciate your warning.

[Bob Salomon]

Why be surprised? Copal shutters do not have intermediate settings for shutter speed. And trying to use them could create problems with the shutter. If you have to vary exposure use either the aperture settings or a ND filter.

If you must have intermediate settings for shutter speeds then investigate the Rollei Linear Motor Shutter Syytem in 0 and 1 sizes.

[Bob Salomon]

New Copal shutters are supplied complete with an instruction book, at least the ones we supply on Rodenstock lenses do. In the instruction manual is an explicit warning to only use marked shutter speeds as the shutter may malfunction. Something you have proved correct.

[D. Kevin Gibson]

"Why be surprised? Copal shutters do not have intermediate settings for shutter speed. And trying to use them could create problems with the shutter."

If you read the post I don't think James was trying use an intermediate setting - it was accidental.

It's also very interesting to know that between 1/2 and 1/4 of a second your exposure will not be marginally off - as may occur between other setting, but seriously off. That is, there is not likely to be any way to rescue the image from this particlauar mistake.

"If you must have intermediate settings for shutter speeds then investigate the Rollei Linear Motor Shutter Syytem in 0 and 1 sizes."

I think I'm gobsmacked - am I right in thinking that particualrly tasty piece of hardware is sold by someone other than HP....! :-0

[Bob Salomon]

"am I right in thinking that particualrly tasty piece of hardware is sold by someone other than HP"

It is sold by several companies. The major one being Rollei.

[Jon_2416]

Typical Saloman. Misunderstands the post, then offers a "solution" that his company is involved with--without identifying his company.

[Bob Salomon]

Sorry Jon, I did not misunderstand the post and I was pointing out that the shutter could actually be damaged by using intermediate speeds. It is not recommended or useful to do so with a Copal shutter.

As for my company we have no connection with Rollei and every lens company sells Copal and Rollei shutters as do most large format camera manufacturers as well as some digital back companies.

So what is your problem? Your response added nothing useful or meaningful to the discussion.