Mounting a lens in a lens board

greenspun.com : LUSENET : Large format photography : One Thread

This must be a hopelessly 'newbie' question, since I haven't found the answer anywhere on the net or in 3 LF books (Kodak, Simmons, Stroebel). FYI, I don't have any lenses or lens boards, yet (hopefully I will next week).

Is mounting a lens in a lens board a critical or precision operation? How is it done? I'd guess the front/rear lens elements have to be separated to fit it in the hole in the lens board, so how does one know that the elements are spaced properly when putting them back together? Do different lens boards require different mounting techniques (Iíll be using Arca-Swiss 110mm boards)? Is it pretty much the same as mounting a lens on an enlarger board? Whatís the accepted orientation of the shutter controls after mounting, or does it matter?

Thanks!

-- Tom Westbrook (tom@twestbrook.com), March 09, 2002

Answers

It isn't terribly critical, and I've done some pretty servicable mounting jobs with layers of matte board and an X-acto knife. The "right" way to do it is to mount the lens board in the 4-jaw chuck of a metal lathe, center it, then bore the hole with a boring bar. If the shutter has an anti-rotation pin, a hole or notch for that is drilled, either by hand, or on the milling machine, depending on what one has available. The rear lens group unscrews from the shutter to allow mounting, and it will repeat its position when screwed back in- moderate pressure, not too tight, not too loose. People have mounted lenses with circle cutters, hole saws, and even Greenlee punches, but for a perfect job you can't beat machine tools.

-- Conrad Hoffman (choffman@rpa.net), March 09, 2002.

Assuming you already have a board of the right size: unscrew the REAR element and the retaining ring, put the lens through the hole from the front, screw down the retaining ring, replace the rear element. Orient it however you like. Some shutters like a number 3 may interfer with camera parts here and there forcing an orientation to accomodate that problem. Screwing the retaining ring on or off is easier with a tool intended for the purpose (like SK Grimes') but if you have nothing else, use two screw driver blades on opposite sides of the ring. If you use only one blade, the ring will bind and never really tighten.

Here are the shutter hole sizes:

Shutter number hole size 0 34.8 mm or 1.362" 1 41.8 mm or 1.636" 3 65.3 mm or 2.560" 3s 2.525"

See the table at: http://www.skgrimes.com/products/index.htm

-- John Hennessy (northbayassociates@earthlink.net), March 09, 2002.


Yes, same thing a mounting a lens to an enlarger lensboard.

Just like enlarger lenses some need to have the back element unscrewed to assemble to the lensboard and others don't. Most lenses used for photography have a shutter instead of the familiar enlarger type iris barrel. But the principle is the same in both cases.

-- Steve Grimes (skgrimes@skgrimes.com), March 09, 2002.


Moderation questions? read the FAQ