How hard/easy to mount lens in a 'new' Copal shutter

[pchaplo]

If I have a used lens such as a Schneider Symmar-S in a malfunctioning shutter, and I have a working Copal 0 (same size), is it feasible for me to DIY swap the shutter? How complicated (or simple) is it?

[Bob Salomon]

Very simple, unscrew the front and back cells from the old shutter, be sure to keep any shims.
Screw the cells into the new shutter replacing any shims from the old shutter.
If the aperture scales are different on the shutters unscrew the scale from the old shutter and install it on the new one.

[Mark Sampson]

Then send the broken one out for repair- they aren't making any new ones.

[pchaplo]

Thanks Bob. I never thought about the aperture scale and shims. Are the shims circular flat rings?


Very simple, unscrew the front and back cells from the old shutter, be sure to keep any shims.
Screw the cells into the new shutter replacing any shims from the old shutter.
If the aperture scales are different on the shutters unscrew the scale from the old shutter and install it on the new one.

[pchaplo]

Good idea. Who do you use?


Then send the broken one out for repair- they aren't making any new ones.

[Bob Salomon]

Thanks Bob. I never thought about the aperture scale and shims. Are the shims circular flat rings?
Yes

[Bob Salomon]

Good idea. Who do you use?

Any camera repair place can service a leaf shutter. That is camera repair 101! However, parts are no longer made, so if yours needs parts that aren’t available then you would have to find a repair shop that either still has new ones or salvaged ones or can make them.

Tempe Camera in Phoenix and
Precision in Austin are two you can try.

[Leigh]

One critical point is that shims are NOT all the same thickness.

Their purpose is to take up the error in the shutter thickness (manufacturing tolerance). One shim or set of shims from one shutter will NOT work with another shutter, even if the same brand. Nor will they work with the same shutter when mounting a different set of lens elements.

- Leigh

[LabRat]

I'll add to get precision calipers and measure the cells back to front in the old shutter, and try the cells again in the new shutter to see if the measurement matches... If the calipers reach, measure front to back on each of the shutters (without cells) to see if they match...

This is a test...

Steve K

[Pfsor]

One critical point is that shims are NOT all the same thickness.

Their purpose is to take up the error in the shutter thickness (manufacturing tolerance). One shim or set of shims from one shutter will NOT work with another shutter, even if the same brand. Nor will they work with the same shutter when mounting a different set of lens elements.

- Leigh

Because you suppose the shims are made for a specific shutter? I suppose they are rather made for a nominal shutter and for a specific pair of lens cells - much more economical that measuring each shutter individually. Because we don't live (and produce lenses) in an ideal world but in a world of economic constraints.

[Pere Casals]

Because you suppose the shims are made for a specific shutter? I suppose they are rather made for a nominal shutter and for a specific pair of lens cells - much more economical that measuring each shutter individually. Because we don't live (and produce lenses) in an ideal world but in a world of economic constraints.

Shims are not added because shutter dimensions variability. For each cells pair Inter-cell spacing can be adjusted to get better performance for center or for corner, for distant or near objects, or to get good average in different situations.

Some lens designs are specially suitable to allow a lens being optimized by adjusting inter-cell spacing. For example convertible lenses normally can be less optimized than others, in the convertible case front and rear cells are individually corrected, in other designs the rear cell corrects the aberrations generated by front cell in the counter sense, and by adjusting the inter cell-distance it is also adjusted how big are the front cell generated aberrations, so the total amount can be adjusted to a minimum for a particular job or for good overall performance.

It is common that samples having very good center performance also have poorer than normal corners, sometimes this can be balanced with more or less shims.

I can be wrong, but this is what I was told by an optician.

[Pfsor]

Shims are not added because shutter dimensions variability. For each cells pair Inter-cell spacing can be adjusted to get better performance for center or for corner, for distant or near objects, or to get good average in different situations.
...
I can be wrong, but this is what I was told by an optician.

That's my understanding too. Otherwise new shutters (when they were still made) would be sold with their shims and not lenses with their shims.

[Pere Casals]

That's my understanding too. Otherwise new shutters (when they were still made) would be sold with their shims and not lenses with their shims.

... then, I'd ask, shutters sold alone without the lens, had all the same shims for the same model ?

IMHO a shutter it is easy to be manufactured with tight tolerances regarding inter-cell spacing... do perhaps incorporate shims to allow to decrease the inter-cell spacing from nominal ?

Were there lenses (of different eras, perhaps, or mm vs inches norms) with different nominal spacing ?

...I guess this would also be useful to tune a common pictorial lens for close-ups, by reducing spacing... just asking...

[Bob Salomon]

... then, I'd ask, shutters sold alone without the lens, had all the same shims for the same model ?

IMHO a shutter it is easy to be manufactured with tight tolerances regarding inter-cell spacing... do perhaps incorporate shims to allow to decrease the inter-cell spacing from nominal ?
New shutters do not come with shims. Lenses are supplied with shims.
Were there lenses (of different eras, perhaps, or mm vs inches norms) with different nominal spacing ?

...I guess this would also be useful to tune a common pictorial lens for close-ups, by reducing spacing... just asking...

[Leigh]

Shims are not added because shutter dimensions variability.
So you expect shutters to be manufactured with zero tolerance, yes?

You realize that would increase the price by a factor of 10 to 100.

Your optician is obviously unfamiliar with manufacturing techniques.

- Leigh

[Pere Casals]

So you expect shutters to be manufactured with zero tolerance, yes?

You realize that would increase the price by a factor of 10 to 100.

Your optician is obviously unfamiliar with manufacturing techniques.

- Leigh

Leigh, making optical flanges with perfect dimensions is something very easy to achieve, this has even been true even for cheap mass produced cameras. For the LF shutters case it is even easier, we only need a mechanical element ensuring the shutter thickness precision, this is way easier than later measuring the spacing and and placing a matching shim, beyond cost this looks a botched job.

If all shims in spare shutters are of same thickness then this would be to acomodate lenses with different inter-cell specs or to have room to lower inter-cell spacing. If shims (in new spare shutters) are different, then you are right, they use shims to overcome a weird manufacturing variability.

Note that some Rodenstock lenses (for example) incorporate different thickness shims to adjust for optimal inter-cell spacing for a particular couple of cells, but not to overcome shutter manufacturing variables...

[Leigh]

they use shims to overcome a weird manufacturing variability.
Pere,

It's a pity you don't understand the concept of "tolerance" in a manufacturing environment.

- Leigh

[Pere Casals]

Pere,

It's a pity you don't understand the concept of "tolerance" in a manufacturing environment.

- Leigh

Leight, I understand it perhaps too much, in fact I'm (sadly) all day long programming machine vision cameras for computer vision based metrology in manufacturing lines... quite boring, really :)...

[Pere Casals]

I'm a Master Tool and Die Maker with several decades of experience.



Do you think making LF shutter flanges with within 0.05mm tolerance is it dificult ?

Copal made clockworks with dozens of 0.001 precision components, but were they unable to make precision optical flanges ? having to add 0.5mm shims for brand's shame?

[BrianShaw]

I really don’t want to join this sh!tstorm but this has fascinated me for years...

I’ve never seen a table of shutters by lenses that indicates the required shim dimension. Why not? If I simply never found one online or in manuals, would somebody please point me to one.

If shimming is so standardized I would expect such data to be readily known and available.

My only experience with a shutter/lens shim was in 1 out of 6 Kodak Retina III’s I’ve overhauled.

[Leigh]

I’ve never seen a table of shutters by lenses that indicates the required shim dimension.
Why not? If I simply never found one online or in manuals, would somebody please point me to one.
That's because tolerance errors are individual, to a specific lens or shutter, not general to a group thereof.

- Leigh

[Leigh]

Do you think making LF shutter flanges with within 0.05mm tolerance is it dificult ?
It's not difficult.

It's expensive.

That's the point you fail to understand.

- Leigh

[BrianShaw]

That's because tolerance errors are individual, to a specific lens or shutter, not general to a group thereof.

- Leigh

Well that's your position, Leigh, which I tend to share. I welcome an answer from those who think otherwise. :)

EDIT: Interestingly, the one time I saw a shim it was paper and I lost it. The camera performed quite admirably without the shim so when I found it I didn't bother installing.

[Leigh]

Leigh, I understand it perhaps too much, in fact I'm (sadly) all day long programming machine vision cameras for computer vision based metrology in manufacturing lines... quite boring, really :)...
That explains much of the misunderstanding.

These shutters were made by people operating machines, not by computers.

Parts produced manually have a much wider range of errors.
Making parts to a tight tolerance manually requires significantly more time ($$$) on the machine.

Now, we have the luxury of measuring individual surfaces while still in the fixture. That was not possible in a manual system. In fact, most parts weren't measured until they got to QC.

- Leigh

[Jim Jones]

Do you think making LF shutter flanges with within 0.05mm tolerance is it dificult ?

Copal made clockworks with dozens of 0.001 precision components, but were they unable to make precision optical flanges ? having to add 0.5mm shims for brand's shame?

A between-the-lens shutter is much more than a simple tube. Between the lens cells are several components that affect their seperation. Any cumulative error in these components could be compensated for with easy-to-lose shims. Better yet, the lens cell mating surface could be machined down after shutter assembly to the desired overall length. The lens elements and their mounts have even more potential for errors. Shims provide the logical say to compensate for this on an individual basis by the lens maker.

[Pere Casals]

It's not difficult.

It's expensive.

That's the point you fail to understand.

- Leigh

In series production making 2 metal flanges of that size matching a distance within 0.05mm is under $0.3.

Of course making a unique custom part has higher costs, because and employee can spend a full morning with it, but with repetitive works an automated lathe makes precision parts at very low cost. If you go to a hardware shop you may find thousands of parts with within 0.05mm precision for lens than 10 cents each.

[Pere Casals]

A between-the-lens shutter is much more than a simple tube. Between the lens cells are several components that affect their seperation. Any cumulative error in these components could be compensated for with easy-to-lose shims. Better yet, the lens cell mating surface could be machined down after shutter assembly to the desired overall length. The lens elements and their mounts have even more potential for errors. Shims provide the logical say to compensate for this on an individual basis by the lens maker.

If the mechanical designer was not absolutely incompetent, it was pretty easy to ensure flange distance, if you disassemble any modern shutter you will always find some simple parts across the shutter body made with precision that are intended to ensure a consistent inter-flange distance.

[Leigh]

but with repetitive works an automated lathe makes precision parts at very low cost.
That's certainly true.

And that's also certainly NOT the point of this discussion.

When these shutters were made, they were done by hand, not on an automated lathe.
In that environment, precision definitely does add to the cost.

- Leigh

[Sal Santamaura]

Very simple, unscrew the front and back cells from the old shutter, be sure to keep any shims.
Screw the cells into the new shutter replacing any shims from the old shutter.
If the aperture scales are different on the shutters unscrew the scale from the old shutter and install it on the new one.

Bob provided a complete answer in his post (#2). Everything after that has served only to confuse the matter.

First, although supplies are dwindling, new Copal shutters are still available. Second, shims are used to fine tune cell spacing so that optical variations can be compensated, not because of shutter manufacturing tolerances. Those optical variations are more than an order of magnitude greater than Copal's thickness tolerance.

Using Rodenstock as an example, shims ranged from 0.5 to 1.5mm. Copal shutters carry a thickness tolerance of ±0.025mm.

[Pere Casals]

That's certainly true.

And that's also certainly NOT the point of this discussion.

When these shutters were made, they were done by hand, not on an automated lathe.
In that environment, precision definitely does add to the cost.

- Leigh

The assembly was made by hand, but the component parts ensuring tolerance were made by automated manufacturing.

Just previous post repeats it: Copal shutters carry a thickness tolerance of ±0.025mm, this ends the debate, IMHO.

[BrianShaw]

Bob provided a complete answer in his post (#2). Everything after that has served only to confuse the matter.

First, although supplies are dwindling, new Copal shutters are still available. Second, shims are used to fine tune cell spacing so that optical variations can be compensated, not because of shutter manufacturing tolerances. Those optical variations are more than an order of magnitude greater than Copal's thickness tolerance.

Using Rodenstock as an example, shims ranged from 0.5 to 1.5mm. Copal shutters carry a thickness tolerance of ±0.025mm.

So who does this fine tuning, Sal... the yenta that’s mating a lens to a shutter? Based on some optical measurements?

[Pere Casals]

that’s mating a lens to a shutter? Based on some optical measurements?

The lens is not mated to a shutter, all modern shutters are equal, what is mated is a front cell to a rear cell, for each pair of cells there is an optimal lens spacing, not because the threads of the cells are not done equal, but because glasses are not all equal, refraction index of a batch may vary slightly (say an 1 per 1000), thermal issues during manufacturing, etc who knows... but optical design may allow a better compensation of aberrations (front+rear) by shimming.

So if replacing a shutter we can use a caliper to check that the new one is same thickness, but the important thing it will be reusing the shimming that mates the front cell to the rear one for best performance.

[Dan Fromm]

Papi, Boyer recomputed lenses for each batch of glass. My friend Eric Beltrando sometimes did that work for his friend M. Kiritsis, Boyer's last owner.

[Pere Casals]

Papi, Boyer recomputed lenses for each batch of glass. My friend Eric Beltrando sometimes did that work for his friend M. Kiritsis, Boyer's last owner.

Just an speculation... if a design may make spherical and chromatic aberrations more or less proportional in the front cell depending on glass, and the same in the rear cell but with aberrations compensating in the other sense... then inter-cell spacing would adjust how big the aberrations are when rays arriving to the rear cell, in order to get an optimal cancellation.

What I say is that if a design is sound enough perhaps shimming could compensate glass variability without recomputing the lens and messing in serial production. Perhaps in most modern computerized designs a priority was alowing a clean compensation of glass variability by a simple shimming... I repeat , just speculating... just realizing the value of that possibility...

[Sal Santamaura]

So who does this fine tuning...As Bob has posted endlessly over the years, the factory does it using elaborate optical measuring equipment. That's why it's important to transfer the original shims when moving cells into a replacement shutter. An independent optical facility could perform similar optimization if 'loose' cells need placement in a shutter or if re-shuttering cells where it's not known whether original shims existed or have been changed.