19" Red dot artar - element spacing

[Ray Van Nes]

I recently picked up a 19" Red Dot Artar mounted in a #4 Alphax shutter. So good , so far. I got it at a low price so I had my friend Bill Peters have a look at it to check it in regard to shutter speeds etc. When he removed the back element, it almost fell out and was not very well threaded. He is going to rectify that. He maestro of the machine lathe. The question for the day , does anyone know the correct spacing of the elements to ensure they are mounted in the correct way.

Thank you
Ray

[Carsten Wolff]

....you mean, length of the lens overall? Or between the two elements? Artars are a symmetrical design. Use the other cell as your guide (?), if it just means you need your correct reassembly, ... but even then.....

[Leigh]

The cell spacing was set at the factory using a very precise jig.

It works like a focusing helicoid but with a very small range and accurate length scale.
The cells are mounted on the jig, which is then adjusted for optimum performance.

The shutter is accurately machined.
Either they choose one with correct dimension, or they use shims on a shorter shutter.

You certainly have no comparable equipment.

- Leigh

[Carsten Wolff]

...see also e.g.:
http://www.largeformatphotography.info/forum/showthread.php?85456-18-quot-Artar-Cell-Spacing

[Bernice Loui]

Post#15,

"Re: 18" Artar Cell Spacing
Actually Goerz were NOT sloppy about spacing whatsoever, that comment should be reserved and used most often with another lens maker....Carl Zeiss, the kings of sloppy optical construction.

As many of you may have found you can't take the cells from one Artar and use the barrel for another, each lens was HAND TUNED to its own specific barrel, its quite rare and I've only had a perfect fit in one case over decades of trying. The focal length of the lens may be 455mm or 17 1/2" approx, does the barrel actually say 18"? If so it may have been a custom job, Goerz did that kinda thing from time to time. Good luck finding a barrel for the lens, all I can suggest is perhaps using a 19" barrel and adding tape to the threads for a fit then once proper sharpness is achieved to silicone the cells in place...kinda rough and ready but saves the expense of shutter mounting."


-Many older vintage lenses were individually hand tweaked to optimize performance and customer needs. Tolerances and dimensions involved are very small typically in less than 0.001". To think simply re-installing the cells to a idealizes spacing will not be optimal for that given set of Goerz lens cells. IMO, contact some one who is technically competent with this speciality work or contact the folks at Schneider or similar to see if they can set this set of lens cells to the spacing as required.


Bernice



...see also e.g.:
http://www.largeformatphotography.info/forum/showthread.php?85456-18-quot-Artar-Cell-Spacing

[Ray Van Nes]

Thank you all. I also tried googling for the info and found it on Apug with all the precise measurements Bill needed.
Cheers
Ray

[Leigh]

...with all the precise measurements Bill needed.
Unless those measurements are for the exact serial number being mounted, they're meaningless.

- Leigh

[Dan Fromm]

Interesting discussion.

Lessee now. Industrial firms such as, in alphabetical order, Fuji, Nikon, Rodenstock and Schneider have made standard barrels for their lenses that matched the standard shutters the cells can also go in. Even Boyer, where production was pretty, um, artisanal managed this. We've discussed fettling and using shims to compensate for slight errors. Our discussions on shims reported shims but not in most lenses.

Why couldn't Goerz work at that level of precision? What's wrong with American manufacturing? You folks make Goerz sound like Leica, who relied on fettling to get out-of-spec parts to work properly together.

[Leigh]

We've discussed fettling and using shims to compensate for slight errors.
Sorry, Dan,

But you misunderstand.

ALL manufactured products have tolerances, from the simplest straight piece of wire to the Eiffel Tower.

Precision costs money. Making a part with a tolerance of +/- 0.001" is more expensive than +/- 0.01".

Every dimension of every lens element and metal component has a tolerance.
A complete lens cell has hundreds of dimensions, each with its own tolerance.
And the acceptable distance between the two cells likewise has a tolerance.

Custom assembly can be cheaper than making everything exactly right.
Lens makers must make a profit on a lens that can be sold at a reasonable price.

- Leigh