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hfsilva
27-Jun-2014, 04:18
Hello all. New member and absolute rookie. Just got my ..y-bought 150 5,6 Apo Sironar S. Mint as advertised, but with the lens cells in reversed positions (front in the back and vice versa). While correcting the situation, two very fine metal washers fell from the lens. Where do these go exactly?
Best regards
hfs

Bob Salomon
27-Jun-2014, 04:24
Ether back to the factory in Germany to be put back on the optical bench or back to the seller for a refund.

Steve Goldstein
27-Jun-2014, 04:43
On any Apo-Sironar-S I've ever seen (135mm, 150mm, 180mm, 210mm) the washers have gone between the front cell and the lens. Same for several different focal lengths of Nikkor-SW. Why not put them there and test the lens to see if it meets your performance expectations?

I suspect the manufacturers would want to avoid washers on the rear cell because removing the cell for lensboard mounting increases chance of loss.

Jim Noel
27-Jun-2014, 08:12
On any Apo-Sironar-S I've ever seen (135mm, 150mm, 180mm, 210mm) the washers have gone between the front cell and the lens. Same for several different focal lengths of Nikkor-SW. Why not put them there and test the lens to see if it meets your performance expectations?

I suspect the manufacturers would want to avoid washers on the rear cell because removing the cell for lensboard mounting increases chance of loss.

Don't you mean between the front cell and the shutter?

karl french
27-Jun-2014, 08:20
That's been my experience as well. I've moved two Sinaron (aka Sironar) lenses out of Sinar DB shutters. In both cases the washers were between the front cell and the shutter.

Steve Goldstein
27-Jun-2014, 08:27
Don't you mean between the front cell and the shutter?

Umm, yeah. My fingers are definitely faster than my brain.

DennisD
27-Jun-2014, 17:52
Apo-Sironar -s, 150 mm .
I 've owned 2 lenses of this type both 150mm.

One had 2 shims between the front element and the shutter housing. The other had no shims at all and was fine.

I often wondered whether the 2nd should have had shims as I bought it used. Who knows what the last guy did ! A shim can fall off easily when the lens is dismounted from the shutter body. A careless person might never be the wiser until, one day, he finds a skinny round "washer" lying on the floor. By then, he'd be scratching his head in wonder.

However, I believe Bob Salomon said that the need for shims is determined by the factory after the lenses and shutter are mated. It's a matter of factory testing and "fine tuning". Some lenses may have no shims, while others might have a few.

Bob, please correct me if I mis-stated anything.

dave_whatever
28-Jun-2014, 04:43
I have a sinaron-se which I bought in its original DB shutter, it didn't have any shims. Performs great.

Bob Salomon
28-Jun-2014, 04:57
Apo-Sironar -s, 150 mm .
I 've owned 2 lenses of this type both 150mm.

One had 2 shims between the front element and the shutter housing. The other had no shims at all and was fine.

I often wondered whether the 2nd should have had shims as I bought it used. Who knows what the last guy did ! A shim can fall off easily when the lens is dismounted from the shutter body. A careless person might never be the wiser until, one day, he finds a skinny round "washer" lying on the floor. By then, he'd be scratching his head in wonder.

However, I believe Bob Salomon said that the need for shims is determined by the factory after the lenses and shutter are mated. It's a matter of factory testing and "fine tuning". Some lenses may have no shims, while others might have a few.

Bob, please correct me if I mis-stated anything.

That is correct

Leigh
28-Jun-2014, 07:31
The shims compensate for slight variation in the actual dimensions of the parts, particularly the shutter thickness (front to back).

All manufactured items have tolerances for all dimensions.
As those tolerances get tighter (more precise dimensions), the cost of making the part goes up substantially.

It's cheaper to make a part with tight but not excessively tight dimensional tolerances, then use washers to accommodate the variations during assembly.

- Leigh

hfsilva
28-Jun-2014, 07:35
Thank you all very much for your learned opinions, gentlemen. I got in touch with Rodenstock and they suggested, as Mr. Solomon did, that I send them the lens. As I am almost sure both washers came from between the front cell and the shutter, I'll give that option a try.
Regards,

Sal Santamaura
28-Jun-2014, 08:46
The shims compensate for slight variation in the actual dimensions of the parts, particularly the shutter thickness (front to back)...The variation in Copal shutter thickness that I've measured from sample to sample is not close to the range of shim washer thicknesses delivered with new Rodenstock lenses I've handled. It seems likely that factory shimming is more related to tuning out optical and mechanical variations in the lens cells themselves.

john borrelli
3-Jul-2014, 05:52
Just curious did Rodenstock give you an estimate for the charge and what it was. This question has come up before and I would be curious to know as would others, I'm sure. Don't forget to insure the lens and pack the lens carefully. I am an amateur when it comes to lens design but here are some thoughts anyway FWIW.

The other option here,for others who might not want to send their lens out, would be to do their own less precise testing. Here you would shoot a scene with and without the shims in a variety of combinations. You would need to take notes to keep the images straight when viewing them under a powerful loupe. I would guess that both shims would be between the front lens cell and the shutter, but other combinations are possible. You could shoot one image with no shims, one image with 2 shims in the front, one with 1 shim in the front and one in the rear(this last one is complicated by the fact that the two shims may be of different widths). Luckily, the order of the 2 shims when together are not an issue as they are just trying to keep the lens cell(s) a certain distance from the shutter, like unscrewing the lens cell the width of the shim(s).

The ironic thing might be discovering something unexpected like the lens takes better closeups in one configuration and better images at infinity in another configuration. Let us know how things turned out, best of luck.

Bob Salomon
3-Jul-2014, 07:21
Just curious did Rodenstock give you an estimate for the charge and what it was. This question has come up before and I would be curious to know as would others, I'm sure. Don't forget to insure the lens and pack the lens carefully. I am an amateur when it comes to lens design but here are some thoughts anyway FWIW.

The other option here,for others who might not want to send their lens out, would be to do their own less precise testing. Here you would shoot a scene with and without the shims in a variety of combinations. You would need to take notes to keep the images straight when viewing them under a powerful loupe. I would guess that both shims would be between the front lens cell and the shutter, but other combinations are possible. You could shoot one image with no shims, one image with 2 shims in the front, one with 1 shim in the front and one in the rear(this last one is complicated by the fact that the two shims may be of different widths). Luckily, the order of the 2 shims when together are not an issue as they are just trying to keep the lens cell(s) a certain distance from the shutter, like unscrewing the lens cell the width of the shim(s).

The ironic thing might be discovering something unexpected like the lens takes better closeups in one configuration and better images at infinity in another configuration. Let us know how things turned out, best of luck.

Let me quote from the Rodenstock distributor price list regarding additional costs for mounting and testing lens cells into shutters:

"The prices shown in our price list are for mounting front and rear cells in shutter delivered by our customer.
The assembly can only be done at Qioptiq Photonics Feldkirchen. We will not deliver front and rear cells unmounted. We insist that the lenses go through our quality control department"

So when you send the lens to the factory for proper mounting in a shutter it is not just a matter of dropping a couple of washers in and that's it. The lens goes through the same procedure that a new lens cells go through so the end user is assured that the lens peforms to its specifications.

Except for the HR Digaron-S/W 90mm lens all other Rodenstock lenses have the same charge for the mounting and testing. The S/W is more expensive to mount and test.

Leigh
3-Jul-2014, 07:27
It seems likely that factory shimming is more related to tuning out optical and mechanical variations in the lens cells themselves.
Sal,

Every component in a lens has a dimensional tolerance. That includes the individual elements, all of the aluminum components in the cell, and the fully-assembled cell itself.

When the design is finalized, the shutter must work with every possible combination of those dimensional errors, which means its greatest thickness must be less than the required cell-to-cell spacing.

At the other end of the tolerance band, the shutter will be substantially shorter than the distance required between the cells. The washers accommodate all possible variations between those two dimensions.

- Leigh

Sal Santamaura
3-Jul-2014, 08:42
The shims compensate for slight variation in the actual dimensions of the parts, particularly the shutter thickness (front to back)...


The variation in Copal shutter thickness that I've measured from sample to sample is not close to the range of shim washer thicknesses delivered with new Rodenstock lenses I've handled. It seems likely that factory shimming is more related to tuning out optical and mechanical variations in the lens cells themselves.


...Every component in a lens has a dimensional tolerance. That includes the individual elements, all of the aluminum components in the cell, and the fully-assembled cell itself.

When the design is finalized, the shutter must work with every possible combination of those dimensional errors, which means its greatest thickness must be less than the required cell-to-cell spacing.

At the other end of the tolerance band, the shutter will be substantially shorter than the distance required between the cells. The washers accommodate all possible variations between those two dimensions...I've fully understood all facets of manufacturing tolerances for more than four decades. An engineering education and career will inculcate one with a complete appreciation of the implications thereof.

Please note that your first post, which my prior post quoted and responded to, included the phrase "particularly the shutter thickness," implying that Rodenstock's use of shims is more related to sample thickness variation of shutters than any other factor. I simply noted that, in my experience, having measured the thickness of numerous Copal shutters and Rodenstock lens shim washers, there is probably more sample variation in the Rodenstock cells' physical and optical characteristics than one finds in Copal shutter thicknesses.

That is all I wrote. Quoting only part of my post and offering a lecture on tolerances was unnecessary.

Leigh
3-Jul-2014, 11:16
I've fully understood all facets of manufacturing tolerances for more than four decades. An engineering education and career will inculcate one with a complete appreciation of the implications thereof.
...
That is all I wrote. Quoting only part of my post and offering a lecture on tolerances was unnecessary.
Perhaps. Perhaps not.
My posts are meant to educate all of our members, not a select few.

I too am an engineer with decades of experience in mechanical design and fabrication.
I doubt that most of our members can claim that.

The seating plane tolerance on all Copal shutters is ±0,025mm (0.001").
That's huge for a precision part.


Sorry to hear you've been inculcated. My best wishes for a speedy and complete recovery. :p

- Leigh

Bob Salomon
3-Jul-2014, 12:22
Perhaps. Perhaps not.
My posts are meant to educate all of our members, not a select few.

I too am an engineer with decades of experience in mechanical design and fabrication.
I doubt that most of our members can claim that.

The seating plane tolerance on all Copal shutters is ±0,025mm (0.001").
That's huge for a precision part.


Sorry to hear you've been inculcated. My best wishes for a speedy and complete recovery. :p

- Leigh

Darn,

For the past 40 years I have been playing poker with the same group of guys and among the 8 of us are two engineers and two lawyers. Boy do we have arguments!

And I can't really comment since my oldest grandson graduated last month as a mechanical engineer and his younger brother just finished his freshman year at Georgia Tech and my brother, daughter, son in law and several others are lawyers.

But the engineers sure can make the games interesting! The lawyers just make it funny!

Leigh
3-Jul-2014, 12:29
my brother, daughter, son in law and several others are lawyers.
Wow, Bob.

I see why you spend all your time on internet fora.

I wouldn't want to associate with those folks either. :rolleyes:

- Leigh

Sal Santamaura
3-Jul-2014, 13:06
...The seating plane tolerance on all Copal shutters is ±0,025mm (0.001")...Which exactly underscores my point. In this post


http://www.largeformatphotography.info/forum/showthread.php?102393-Ring-for-Rodenstock-Sironar-N-lenses&p=1015985&viewfull=1#post1015985

Bob notes that the shimming washers range from 0.5mm to 1.5mm thick. Sometimes the factory needs to use two of them. So Copal shutter thickness tolerance appears to indeed be one of the smaller factors driving Rodenstock lens shimming.

Leigh
3-Jul-2014, 13:19
Sal,

You claim to be an engineer, yet you apparently have no clue what cumulative tolerances are.

The tolerances of the components in the lens cells are certainly less than that of the shutter, but the cumulative error may be more.

- Leigh

Bob Salomon
3-Jul-2014, 13:26
Which exactly underscores my point. In this post


http://www.largeformatphotography.info/forum/showthread.php?102393-Ring-for-Rodenstock-Sironar-N-lenses&p=1015985&viewfull=1#post1015985

Bob notes that the shimming washers range from 0.5mm to 1.5mm thick. Sometimes the factory needs to use two of them. So Copal shutter thickness tolerance appears to indeed be one of the smaller factors driving Rodenstock lens shimming.

That is assuming that all of the various thickness washers are used on Copal shutters. They may not be. Some maybe just for the Rodenstock eShutter or the Rollei Linear Motor shutters or old Compur and Prontors. Or maybe old Copals needed different shims then later ones, etc.

mdarnton
3-Jul-2014, 13:40
All the chatter aside, can we draw any conclusions from Schneider's habit of recommending the back element of convertible lenses, but Rodenstock's preference for using the front, combined with their preference in those lenses of putting the shims in front, where they won't run the risk of getting lost? Habit counts for a lot, especially considering that with Rodenstock's method you don't run the risk of losing the shim when putting the lens on a board, either.

I'm betting that IF they have a consistent policy of where to put the shims (and why wouldn't they?), it's in front, then.

Bob Salomon
3-Jul-2014, 14:02
All the chatter aside, can we draw any conclusions from Schneider's habit of recommending the back element of convertible lenses, but Rodenstock's preference for using the front, combined with their preference in those lenses of putting the shims in front, where they won't run the risk of getting lost? Habit counts for a lot, especially considering that with Rodenstock's method you don't run the risk of losing the shim when putting the lens on a board, either.

I'm betting that IF they have a consistent policy of where to put the shims (and why wouldn't they?), it's in front, then.

Except the convertibles are decades old and that is not the best way to compare. Especially since that convertible lens was replaced with the Sironar-S which was replaced by the Sironar-S MC which was replaced by the Apo Sironar-N in 1986.
What worked 40 years ago with the technology used back then is not necessarily the same way they work now.

I always felt that removing the rear element, especially when working outdoors, was much better for the shutter since when the front element is off the leaves of the shutter are exposed to the dust and envronmental hazards of the outdoors more then Rodenstock's way. But the actual answer lies in the formulation of the cells. Schneider's and Rodenstock's lens design for their convertibles were slightly different.

mdarnton
3-Jul-2014, 14:04
Still gotta put 'em on boards. That hasn't changed.

onnect17
3-Jul-2014, 14:59
The variation in Copal shutter thickness that I've measured from sample to sample is not close to the range of shim washer thicknesses delivered with new Rodenstock lenses I've handled. It seems likely that factory shimming is more related to tuning out optical and mechanical variations in the lens cells themselves.

I think so too.
Even the difference in the torque applied by the user mounting the glass in the shutter introduces at least another +/-0.1mm.
Testing the optimal performance is not hard, keeping in mind the design of the apo lens includes corrections to adjust for the order and thickness of the color film emulsion layers. So it should be tested with color emulsion or a foveon type sensor.

Leigh
3-Jul-2014, 16:03
I always felt that removing the rear element, especially when working outdoors, was much better for the shutter since when the front element is off the leaves of the shutter are exposed to the dust and envronmental hazards of the outdoors more then Rodenstock's way. But the actual answer lies in the formulation of the cells. Schneider's and Rodenstock's lens design for their convertibles were slightly different.
There's a huge difference in bellows requirement if you use the front cell v. the rear cell.

The distance from the film to the rear node of the lens always equals the optical focal length.
That is true regardless of whether you use a simple single element or a 20-element wide angle.

The rear node of the rear cell will be much closer to the film than the rear node of the front cell.

- Leigh

Sal Santamaura
3-Jul-2014, 16:52
That is assuming that all of the various thickness washers are used on Copal shutters. They may not be. Some maybe just for the Rodenstock eShutter or the Rollei Linear Motor shutters or old Compur and Prontors. Or maybe old Copals needed different shims then later ones, etc.I've purchased brand new Copal-shuttered Rodenstock lenses in recent years that used multiple shim washers whose thickness was more than 1mm each. No assumption involved.


...You claim to be an engineer, yet you apparently have no clue what cumulative tolerances are...Ad hominem attacks demean only the attacker.


...The tolerances of the components in the lens cells are certainly less than that of the shutter, but the cumulative error may be more...Which has what to do with your impying that shutter thickness variation is a "particularly" dominant reason for needing shims? If anything, this latest statement refutes your implication.

You're ignoring the fact that Rodenstock's final testing/shimming accounts not only for cumulative mechanical tolerances in the cell assembly dimensions but also optical variations of the elements and their alignment within those cells. That's why it's incorrect to imply that a shutter thickness tolerance of ±0,025mm (0.001") is an especially important reason for shims, given that shims nearly two orders of magnitude thicker than potential shutter thickness variation have been used. Again, that's the only thing I commented on in post #12. I took issue with your emphasis on the shutter, not with the fact that there are other sources of variation.

Leigh
3-Jul-2014, 17:13
I took issue with your emphasis on the shutter, not with the fact that there are other sources of variation.
And what business is that of yours?

My comments are based on my experience of servicing lenses for about 40 years.

Every one of your comments has been based on your experience.

Kindly enlighten me as to the difference between those sets of information, which would make yours more valid than mine?

My comment about the shutter tolerance was because it's the only factor that can be changed with shims.
All of the other dimensional errors are internal to the cells and cannot be changed in the field.

- Leigh

Sal Santamaura
3-Jul-2014, 17:37
...I took issue with your emphasis on the shutter, not with the fact that there are other sources of variation.


And what business is that of yours?...The OP asked a question. Rather than join in with a simple answer to the question (shims go between shutter and front cell) you delivered a lecture on tolerances. Your lecture incorrectly implied that shutter thickness variation was a particularly important reason why shims are used. As a member of this community for 11 years longer than you have been, I try to keep the archive as free of error as possible, just in case someone performs a search and thinks the threads they find here are authoritative. It's my business because I make it my business.


...My comments are based on my experience of servicing lenses for about 40 years...So? I frequently encounter drivers with more experience than that behind the wheel who shouldn't be permitted to operate a motor vehicle. :)


...Every one of your comments has been based on your experience.

Kindly enlighten me as to the difference between those sets of information, which would make yours more valid than mine?...Experience has nothing to do with this subject. Facts don't vary depending how experienced someone is observing or missing them.

Leigh
3-Jul-2014, 17:42
Experience has nothing to do with this subject.
You have a conveniently short memory. From post #28:

I've purchased brand new Copal-shuttered Rodenstock lenses in recent years...

I find it interesting that you were unable to answer a very direct question:

Kindly enlighten me as to the difference between those sets of information, which would make yours more valid than mine?


- Leigh

Sal Santamaura
3-Jul-2014, 18:35
...Experience has nothing to do with this subject...


You have a conveniently short memory. From post #28:...


I've purchased brand new Copal-shuttered Rodenstock lenses in recent years that used multiple shim washers whose thickness was more than 1mm each...Unlike you, I've not truncated the quoted sentence. My memory is not short. What I wrote refers to specific measurements of specific shims, not generic "experience."


...I find it interesting that you were unable to answer a very direct question:...


...Kindly enlighten me as to the difference between those sets of information, which would make yours more valid than mine?...Your very direct question conflates experience with facts/measurements. It is unanswerable in any rational sense. You are attempting to convince readers that your long experience validates an implication (shutter thickness is the principle reason why shims are necessary) which is incorrect. Your "set of information" is neither quantitative nor comparable to mine. Essentially, you're pulling the old "because I'm your father and I say so" routine. It won't work on me.

Leigh, I've attempted to keep this factual and within forum guidelines, but you're making it very difficult. Perhaps that's your intention. In any case, you come across as abrasive and a know-it-all. When one small aspect of your post is disputed, you launch an all-out attack on anyone who dares take such a step. It doesn't reflect well on you or the community. I strongly suggest you step back and consider the possibility that I might be correct before firing another volley.

The OP has received good information and advice. His shims, if they are actually related to his lens, belong between its front cell and shutter. To be absolutely certain of lens performance, he should send it to Rodenstock for testing/adjustment. All the rest is unnecessary.

Leigh
3-Jul-2014, 18:51
The OP has received good information and advice.
His shims, if they are actually related to his lens, belong between its front cell and shutter.
To be absolutely certain of lens performance, he should send it to Rodenstock for testing/adjustment.
I certainly agree with that.

- Leigh

onnect17
3-Jul-2014, 19:11
Just checked the thickness of the washers in a couple of 300mm apo lens. One is 0.2mm and the other one 0.3mm. I got the impression based on previous posts that the thinest washer was the 0.5mm. I hope Bob can explain what I am missing.

Bob Salomon
4-Jul-2014, 04:47
Just checked the thickness of the washers in a couple of 300mm apo lens. One is 0.2mm and the other one 0.3mm. I got the impression based on previous posts that the thinest washer was the 0.5mm. I hope Bob can explain what I am missing.

Nope, I only passed on an answer that I got when someone asked to buy some washers. These things are not in the price list from the factory so we have no printed reference to look it up in. And, as I posted earlier, the factory insists that they only do these re-mountings so they are sure that the lens performs as it is specced to.

Bob Salomon
4-Jul-2014, 05:01
There's a huge difference in bellows requirement if you use the front cell v. the rear cell.

The distance from the film to the rear node of the lens always equals the optical focal length.
That is true regardless of whether you use a simple single element or a 20-element wide angle.

The rear node of the rear cell will be much closer to the film than the rear node of the front cell.

- Leigh

These convertible lenses were made for photography usually by photographers and the protection of the shutter and its blades may have been more important to the factory 40 or more years ago then an extra inch or two of extension. Plus a lot of those older shutters had many shinier bits around that front of the shutter that could create flare that would have been eliminated simply by leaving the front group in.

When I was shooting as a studion owner back in the 60s and 70s with mostly Sinar P Expert outfits in 45, 57 and 810 I had plenty of rails and regardless of brand, when I converted lenses, I always took off the back element. Among other advantages the lens converted this way, used the same size filters, converted or not. Removing the front meant that the back required filter and that, besides adding additional filters to carry, further reduced the performance by adding the filter between the glass and the lens.
Since I had plenty of rail, and bellows, any additional extension simply wasn't important.

Bernice Loui
4-Jul-2014, 08:52
Un-limited rail extension of the Sinar is only one of the reasons why the Sinar has been a Fave for over 30+ years. It is one of the few VC systems that removes camera limitations from optics used at the trade off of light weight and easy portability.

The fewer camera / optics limitations one is forced to deal with, the easier it is to concentrate on how make create images with the given tools.

As for the shims, they are part of the factory optical alignment for a given lens cell set and shutter. The factory spent and invested time, energy, resources and effort to install a very specific set of high precision spacers (not "washers") to a given lens cell set, why does anyone want to dis-respect this fact ?

Not too long ago, I converted a Rodenstock Grandagon from Sinar DB to Copal# 1 shutter, the Copal shutter had to be lapped a few thousands of an inch less to achieve identical cell spacing of the Sinar DB mount. Anything less would have resulted in less than ideal optical performance from the Grandagon.

Optics are very high precision devices and the mechanical precision required for them to deliver their designed in optical performance must be understood and respected. It is that simple.



Bernice



These convertible lenses were made for photography usually by photographers and the protection of the shutter and its blades may have been more important to the factory 40 or more years ago then an extra inch or two of extension. Plus a lot of those older shutters had many shinier bits around that front of the shutter that could create flare that would have been eliminated simply by leaving the front group in.

When I was shooting as a studion owner back in the 60s and 70s with mostly Sinar P Expert outfits in 45, 57 and 810 I had plenty of rails and regardless of brand, when I converted lenses, I always took off the back element. Among other advantages the lens converted this way, used the same size filters, converted or not. Removing the front meant that the back required filter and that, besides adding additional filters to carry, further reduced the performance by adding the filter between the glass and the lens.
Since I had plenty of rail, and bellows, any additional extension simply wasn't important.

Leigh
4-Jul-2014, 10:34
Optics are very high precision devices and the mechanical precision required for them to deliver their designed in optical performance must be understood and respected. It is that simple.
Exactly.

- Leigh

Leigh
4-Jul-2014, 10:38
These convertible lenses were made for photography usually by photographers and the protection of the shutter and its blades may have been more important to the factory 40 or more years ago then an extra inch or two of extension.
Hi Bob,

My comments were intended for those considering convertibles for use with field (folding) cameras, many of which do not have interchangeable bellows. In this situation the difference between front-cell and rear-cell usage can be the difference between being usable and not being usable on a particular camera.

- Leigh

Kevin J. Kolosky
5-Jul-2014, 17:54
Not too long ago, I converted a Rodenstock Grandagon from Sinar DB to Copal# 1 shutter, the Copal shutter had to be lapped a few thousands of an inch less to achieve identical cell spacing of the Sinar DB mount. Anything less would have resulted in less than ideal optical performance from the Grandagon.

Optics are very high precision devices and the mechanical precision required for them to deliver their designed in optical performance must be understood and respected. It is that simple.

Bernice

I am just curious. Did you expose some negatives with the copal 1 shutter before you lapped it and then compared those negatives with ones made after the lapping was accomplished? If so, what exactly did you see as the difference?

Leigh
5-Jul-2014, 18:55
the Copal shutter had to be lapped a few thousands of an inch less to achieve identical cell spacing of the Sinar DB mount.
Hi Bernice,

I think we have a translational error here. Did you mean "a few ten-thousandths (0,0025mm = 0.0001")"?

1) The length tolerance on Copal shutters (including Sinar DB) is +/- 0,025mm (.001"), so worst-case difference between any two would be 0,050mm (.002"). An average sample-to-sample difference would be half that, so only one thousandth of an inch.

If you had to remove "a few thousandths of an inch", one or both shutters were waaaay out of spec.

2) Lapping is a very delicate and precise method used to remove extremely small amounts of metal, fractions of one thousandth, or even millionths of an inch. Taking off several thousandths using that method would require several days of work, even for soft metals like aluminum.

Special jigs or fixtures are required to maintain parallelism of opposing faces.

- Leigh