Lens spacing

[Hening Bettermann]

Hi!

When mounting a lens into a shutter, the spacing of the front and rear cells may have to be adjusted in relationship to each other and to the aperture plane by means of thin spacing rings (shims). How exactly is this measured, and which instruments does it require?

It is not that I want to do it myself. The background:
On a norwegian photo forum, I asked who here in Norway might be able to mount a lens into a shutter. (A taking lens into a fitting shutter, not the adapting of a barrel lens.) I was referred to the former Sinar representative. I called him and he said yes. But when I detailed my question to include the spacing, the answer changed into no.
When I asked who could, he said that they had sent lenses to Schneider in such cases. But while Schneider may be willing to deal with an Angulon, they may not be thrilled about an Apo Ronar or an A Fujinon. Also, in order to keep shipping cost down, I would prefer to send all the stuff to one and the same address.

So, when I try to find somebody else, I feel I have to ask how exactly they do it, and if they have the tools required.

Grimes probably has, but they don't answer my e-mails.

Good light - Hening.

[Juergen Sattler]

Hi Hening, whenever I needed something done from SK Grimes I called them and always got an answer - I think they are overwhelmed with orders and just don't get around answering email. Why don't you give them a call - I am sure they'll be able to do the job for you.

[ronald moravec]

Second the S K Grimes.com

[Donald Qualls]

I've actually gotten e-mail replies from Grimes recently, inquiring about retaining rings vs. flanges (and getting good news on pricing, I might add -- I was fortunate to find the shutters I own without rings have standard #0 threads). Might need to include suitable keywords in the subject to keep your e-mail out of the spam bin...

Meantime, however, ISTM that you'd significantly change the focal length if the element spacing were incorrect. Am I correct in thinking the glass you have is already in cells, and that the cells match the threads in the shutter you wish to use? If so, you should be able to simply screw them in snugly, check that the focal length (from aperture to film plane) is within about 2% of the figure engraved on the name ring, and go take pictures -- they'll normally already have any shims they require inside the threaded cells, which were made to provide correct element spacing when installed in a standard shutter (assuming, at least, that all components were made after about 1930).

[Leigh]

...check that the focal length (from aperture to film plane) is within about 2% of the figure engraved on the name ring...

Sorry to disagree, but that's not correct.

The distance from the mounting plane (front of the lens board) to the film should equal the published Flange Focal Length for the lens, which may be quite different from the optical focal length engraved on the lens.

- Leigh

[John Koehrer]

Sorry to disagree, but that's not correct.

The distance from the mounting plane (front of the lens board) to the film should equal the published Flange Focal Length for the lens, which may be quite different from the optical focal length engraved on the lens.

- Leigh

But the shims discussed have no bearing on the mounting plane.
The Q is lens spacing and shims.

[Leigh]

But the shims discussed have no bearing on the mounting plane.

If you'll read the text quoted in my post #14 you'll find that I was objecting to the confusion of optical focal length with flange focal length.

- Leigh

[renes]

The distance from the mounting plane (front of the lens board) to the film should equal the published Flange Focal Length for the lens, which may be quite different from the optical focal length engraved on the lens.

- Leigh

Is it true even with lenses having "equivalent focus" engraved?

I made a few spacing cells test with "Conley Anastigmat Series V Equivalnet Focus 7-inch" I own. Even I had put them into the shutter as close possible to each other, never reached 7inch focal lenght - the closest was 190mm. Actually 7inch I got only measuring the distance from rear lens (outer surface) to the film plane. But as I know - correct me if I am wrong - "equivalent focus" for symetrical lenses - as my Conley - means distance from the aperture plane, and never refers to back focus distance.
I am fully confused.

[Nick Morris]

Hello,

I had lens cells that I tried to have mounted to a shutter. It can be a difficult and expense job. The spacing is important, and can be critical for some lens cells. I believe SK Grimes can do it, but I think only if the cells are currently mounted, either in a shutter or barrel, and the proper spacing can be determined from the existing mount. They did not believe they could do it properly for my Dagor cells without an exsisting mount.

[Emmanuel BIGLER]

My feeling was similar to Donald's ; I clearly remember a French LF tutorial book of the seventies stating that view camera lenses were designed to be relatively insensitive to mis-spacing in order to make the exchange of lensboards easy with simple tools.

This, until I read this notice on the official Schneider Kreuznach web site.
www.schneider-kreuznach.com/service/service_e.htm


* Our ranges Super-Angulon (incl. XL types), Super-Symmar XL, Super-Symmar HM, Apo-Componon and Digitar can be only repaired at Schneider-Kreuznach. To optimize the optical parameter in the best possible way an exact re-adjustment of these lenses after repair is absolutely necessary.

* Complete shutters should be only exchanged by Schneider Kreuznach directly (also here re-adjustment).


My conclusion is simple.
You can do what you wish with older standard and long focal lengths. Dissassemble. Swap boards. Swap shutters. Remount. Adapt. And forget about shims.

But for modern wide angle lenses, any kind & any manufacturer, the most critical lenses being ultra-wide angle and 'digital' series, do it at your own "risk" if you believe in what Schneider Kreuznach people officially post on their web site.

To me this is the price you have to pay for the improved performance between and old 'not-super' Angulon(TM) and a brand new super-aspherical-wide-top-notch ;-);-)