Shutter Swap for Schneider Symmar

[Fragomeni]

Hi all. I have a Schneider Symmar 210mm convertable lens originally set in a Synchro-Compur shutter. The Synchro-Compur is shot and is probably not repairable. I spoke with S.K. Grimes yesterday and they said that the lens elements fit straight into a Copal 1 shutter. I spoke to them about purchasing a shutter and having them etch a new aperture scale but the time frame is cutting it a little too close for when I'll need to be using the lens. I ended up finding an unused spare Copal 1 shutter in one of my drawers that I'd forgotten about. The elements screw in just as S.K. Grimes said. They did not mention needing shims or anything and said that the elements go right into a Copal 1 which seems to indeed be the case. My last concern is the aperture scale. My question is, can I remove the aperture scale from the original Synchro-Compur shutter and fit it to the new Copal 1? All dimensions and openings appear to match between the two so I would assume that as long as I line up the scale properly in relation to the Copal 1's max opening it should work. Can I do this? Also, I found this post (http://www.largeformatphotography.info/forum/showpost.php?p=77281&postcount=4) describing a fairly simple way of making a new scale if I need to go that route. Any help would be appreciated. I'd like to take care of it here rather then having to send it out because of my schedule. Thanks!

[Kevin Crisp]

You should be able to swap the lens over to the new shutter with no problems at all. You shouldn't need shims.

On your second question, and without the benefit of having a Compur in front of me, don't the aperture numbers on the scale bunch up as the aperture gets smaller? Whereas the Copal is linear and evenly spaced? If so, then using the same scale won't work.

On the other hand, you can set the old shutter at f:16, for example, and mark f:16 on the copal by comparing the two apertures. The relative crudeness of the opening on the Copal will make some estimation necessary, but this can be done. When you have time, Grimes can make you are proper scale for the Copal. Obviously with a meter on the ground glass you could check your estimations if you have any doubt. Good luck. A convertible Symmar can be a terrific lens.

[Fragomeni]

Indeed the numbers do bunch up on the Synchro-Compus. I didn't think about one being linear and the other not. Looks like I'll need to make the scales for the Copal (or eventually have Grimes make some for me). Thank you for your help Kevin!

[Kevin Crisp]

Seriously, you can eye ball them and make a decent temporary scale. Use the white tape from a P-Touch labeler, write on it with a Sharpie, and you're good to go. I've done this several times and many years later I'm still using my temporary scales.

[Fragomeni]

The lable tape is a great idea. I was wondering what I'd use.

[Leigh]

You shouldn't need shims.
This cannot be determined until the cells are mounted on the shutter and the assembly checked on a precision collimator.

All manufactured products have tolerances. If the shutter length is a tad shorter than the cells need, you must add shims.

Granted, that doesn't happen very often.

- Leigh

[Kevin Crisp]

I've done this maybe 6 times or more on convertible symmars, and checked with my caliper that is good to 0.001 inches, which I think is precise enough to measure a tad, and every one has been right on the money.

If you want to pay somebody to check your work, go for it. I think it will be fine without that.

[Leigh]

...and checked with my caliper that is good to 0.001 inches, which I think is precise enough to measure a tad, and every one has been right on the money.
Even if your shutters are all exactly the same dimension, it doesn't tell you what spacing the cells of a particular pair require for optimum focus.

I can measure shutter lengths to ±50 millionths of an inch. That still doesn't tell me what spacing the cells want. :p

It all comes down to what level of precision is required for the application.

- Leigh

[Fragomeni]

Yea, when I spoke with S.K. Grimes I asked if anything needed to be machined. He said no machining was necessary and that they simply screw it into a new Copal 1 and make new aperture scales and thats it. He looked at his spec sheet for the specific lens and clarified this for me so I think I'm safe not worrying about shims.


It all comes down to what level of precision is required for the application.

When it comes down to it that is exactly right.

[Kevin Crisp]

This forum has a great capacity for overcomplicating things. Just do it and go make some photographs.

[Fragomeni]

Hahaha! Agreed, but knowledge (even if its overly complicated) can be a very motivational force in the right hands! Anyway, I'm off to buy some label tape! Thanks again!

[Fragomeni]

Just wanted to follow up here with how I went about doing the shutter swap with the new aperture scales.

I tried the method that I linked to in the original post but I had problems with that method for some reason. I did a little more research and came up with a very similar method that worked wonders. After speaking with S.K. Grimes I confirmed that my Schneider Symmar would indeed fit directly into a modern Copal 1 with absolutely no machining. The front and rear threads and overall important dimensions of the Copal 1 shutter are identical to the dimensions of the original Synchro-Compur shutter that the lens came in. I also found that the max opening of the apertures are the same as well. This important piece of information allowed me to extrapolate all of the other aperture points using the following method:

1) I set up a light box (with perfectly even illumination across it's illuminated area) on a book shelf at about head hight with its illuminated surface facing out toward me.
2) Focused the lens at infinity and then without changing focus I placed it directly in front of the light box at a close distance (maybe 5-7 inches away).
3) I opened the aperture all the way (I've confirmed that this point is f5.6).
* Even though all of the information I found said that the max aperture on the Copal 1 is the same as the Synchro-Compur, I did a visual test to be sure. I compared an image of a grey card photographed by a known lens at f5.6 @ 1/250 (this speed gave me zone V using Fuji FP3000b for a quick visual check) to the Symmar in the Copal 1 at max aperture @1/250 and indeed it was a visual match.
4) After opening the aperture all the way, I set up my spot meter (Pentax V 1 degree) to meter one central spot on the ground glass. I was able to use the bed of the camera to fix the meter in place which made me feel more consistent since the meter not moving through the process insures that the exact same place on the ground glass is being measured throughout all of the stops (no variance in the spot being metered).
5) I took a reading at max aperture and then slowly stopped it down until it was exactly 1 stop less light. I then marked the location of the stop on the aperture scale.
* For the aperture scale, I just unscrewed the scale that was on it and spray painted it white and re-attached it.
6) I repeated step 5 throughout the range of the aperture and with the meter metering the same spot without moving. When finished, I wrote in the numbers for each stop and then tested the lens. This time it was a success! I tested it against a known lens and shot a box of fp3000b in various lighting conditions and everything came out right on point.
The lens is convertible so I'll use the same process to work out the aperture scale for its other focal length as well.

Thanks to all for the help!