Beginner's Question about LF Shutters

Prospero · Jan 1, 2007

Hi all. I recently managed to get hold of a Rodenstock Sironar-N 180mm lens at what I thought was a pretty good price. The lens is in good condition but it came mounted in a "Polaroid Prontor" self-cocking shutter which is rather odd - it has one cable connection for B (which you also use to lock it open for composing) and another for the timed shutter speeds. Also, the shutter is quite sticky on the slower speeds and although flushing it with lighter fluid helped a bit, it is still not quite right.

So I am thinking about getting hold of a Copal 1 shutter to mount it in. But I've never done this and realise that I don't know the answer to a couple of fundamental questions:

1. Is the spacing standard - can I just screw the front and back bits in to the new shutter? If not, how does one establish the correct spacing?

2. I've never thought about this before, but clearly the maximum aperture is a function of the lens, not the shutter. And since I vaguely recall that apertures are actually expressed as a ratio of the focal length, then the physical aperture size for -say - f22 must be different for a 180mm lens than for a 90mm lens. But you don't see shutters advertised as being "for" specific aperture ranges, or "for" specific focal lengths. All this is making my brain hurt - would appreciate any advice.

thanks

Stewart

David H. Bebbington · Jan 1, 2007

1) Short answer yes - if your lens was fitted to the old shutter without shims, it should fit the new one too. Conversely, if any shims or spacers are present, don't lose them!

2) Shutter/iris assemblies of course accept all lenses of the appropriate size, without regard to focal length and aperture. They are then fitted with an appropriate aperture scale. If your lens is an f5.6, you might well find a shutter with a scale for this aperture already on it, otherwise you will need to get a suitable scale engraved (or make allowance in your head, or make your own scale from a sticky label!).

Regards,

David

Roger Hicks · Jan 1, 2007

Stewart Skelt said:
Hi all. I recently managed to get hold of a Rodenstock Sironar-N 180mm lens at what I thought was a pretty good price. The lens is in good condition but it came mounted in a "Polaroid Prontor" self-cocking shutter which is rather odd - it has one cable connection for B (which you also use to lock it open for composing) and another for the timed shutter speeds. Also, the shutter is quite sticky on the slower speeds and although flushing it with lighter fluid helped a bit, it is still not quite right.

So I am thinking about getting hold of a Copal 1 shutter to mount it in. But I've never done this and realise that I don't know the answer to a couple of fundamental questions:

1. Is the spacing standard - can I just screw the front and back bits in to the new shutter? If not, how does one establish the correct spacing?

2. I've never thought about this before, but clearly the maximum aperture is a function of the lens, not the shutter. And since I vaguely recall that apertures are actually expressed as a ratio of the focal length, then the physical aperture size for -say - f22 must be different for a 180mm lens than for a 90mm lens. But you don't see shutters advertised as being "for" specific aperture ranges, or "for" specific focal lengths. All this is making my brain hurt - would appreciate any advice.

thanks

Stewart

Dear Stewart,

There is a free module about exactly this in www.rogerandfrances.com. Go to The Photo School > How Do I...? > Re-shutter a lens. This should answer most or all of your questions.

Cheers,

Roger

Prospero · Jan 1, 2007

Thank you, David and Roger. I guess the simplest way of calibrating the apertures on the new shutter will be to compare it with the old one.

By the way Roger - all this is your fault. I bought "Medium and Large Format Photography" by you and Ms Schultz a few years ago. At that stage I was just getting into MF, but here I am now with a Horseman 45. It's a slippery slope.

Dave Miller · Jan 1, 2007

Stewart Skelt said:
Thank you, David and Roger. I guess the simplest way of calibrating the apertures on the new shutter will be to compare it with the old one.

By the way Roger - all this is your fault. I bought "Medium and Large Format Photography" by you and Ms Schultz a few years ago. At that stage I was just getting into MF, but here I am now with a Horseman 45. It's a slippery slope.

It's a 10x8 for Christmas then?

Roger Hicks · Jan 1, 2007

Dave Miller said:
It's a 10x8 for Christmas then?

Nah -- not worth pissing around with small formats. 11x14 is where LF starts!

Actually I prefer 5x7/13x18/half plate. At a 2x enlargement I defy anyone to tell the enlargement from a contact print. I also like 56x72mm, 3-up, which is within 3mm of whole-plate...

Cheers,

R.

Roger Hicks · Jan 1, 2007

Stewart Skelt said:
Thank you, David and Roger. I guess the simplest way of calibrating the apertures on the new shutter will be to compare it with the old one.

By the way Roger - all this is your fault. I bought "Medium and Large Format Photography" by you and Ms Schultz a few years ago. At that stage I was just getting into MF, but here I am now with a Horseman 45. It's a slippery slope.

Dear Stewart,

Oh, dear. Sorry...

Incidentally, Frances and I will have been married for 25 years this June. We'd both been married before (once each) but she was quite emphatic aboit keeping her maiden name, having changed it (to Thresher) the first time she was married. I completely agree with her: it's a bizarre tribal custom.

Seriously, though, do consider 5x7. As you may have discovered by now, there's another free module in the Photo School, called 'The Large Formats'.

And with your existing shutter, I'd try a more aggressive solvent plus some watch oil. That really is the route I'd take, but then, I am very fond of press (self-cocking) shutters.

Cheers,

R.

raucousimages · Jan 1, 2007

You can order F stop scales for Copal shutters. You need to know the shutter size (copal 0,1,3) and the length of the lens. I found some for a Copal 3, 250mm that needed new ones but I don't rember who had them. Try S.K. Grimes.

Prospero · Jan 2, 2007

raucousimages said:
You can order F stop scales for Copal shutters. You need to know the shutter size (copal 0,1,3) and the length of the lens. I found some for a Copal 3, 250mm that needed new ones but I don't rember who had them. Try S.K. Grimes.

Thank you!!

Prospero · Jan 6, 2007

One more question: if one buys a new Copal shutter from - eg - B&H, what aperture scale does it come with?

Roger - I had another go at the Prontor with solvent. It is now stuck open. I can only assume that I managed to redistribute the gunk through the innards. I think I can see how to get the front off so I will probably try opening it up. Nothing to lose.

Roger Hicks · Jan 6, 2007

Stewart Skelt said:
One more question: if one buys a new Copal shutter from - eg - B&H, what aperture scale does it come with?

Roger - I had another go at the Prontor with solvent. It is now stuck open. I can only assume that I managed to redistribute the gunk through the innards. I think I can see how to get the front off so I will probably try opening it up. Nothing to lose.

There's a notched ring around the hole for the lens. One of the notches has a stop-screw in it. On the Copal-Press illustrated in the 'How Do I...' in the Photo School at www.rogerandfrances.com you can see all this. Measure the front-to-back thickness of the shutter before you take it apart, and mark the position of the stop-screw on the ring. Undo the stop screw; unscrew the centre ring; remove (carefully). Everything should be obvious after this.

If these shutters work at all, i.e. don't have any broken bits inside, then sluicing out with trike or something similar should solve the problems -- especially with the front off.

Good luck.

Cheers,

R.

Beginner's Question about LF Shutters

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