Mounting lens on a board - am I stupid?

[Dietrich Speer]

It seems like every time I try to take another step in the direction of becoming a brilliant LF photographer, I have to post a question here.

Here is my problem:

I am trying to mount my precious little 90mm Angulon on a recessed lens board for my Technika III. The whole is what it's supposed to be - just slightly wider than the thread.

Every time I try to do this really really carefully with the help of my newly acquired deluxe SKGrimes spanner wrench, the lens moves slightly off center , which results in the FStop - ring being blocked.

Is there a trick to this?

Sorry - I guess this sounds really stupid to most of you, but I am stuck. Thanks for any help!

Dietrich Speer

[Doremus Scudder]

Dietrich,

You are not stupid, the mounting hole in your lens board is simply too big. The ideal solution would be to exchange your board for one with a proper sized hole. This may not be financially feasible. You could try to make a shim or spacing washer out of something that was the same thickness as the lens board to hold the lens centered in the hole. I assume that you feel that the f-stop ring would not be blocked if the lens were centered correctly on the board, i.e. that the recessed opeining is large enough to allow the lens to fit and be manipulated as necessary. Make sure also that there is not something binding between the lens board and the bottom of the lens. Keep at it, you'll find a solution eventually. Good luck,

[Tim Curry]

Check to see that there isn't a "step" on the bottom side of the locking ring. If there is and the lens moves, you can have a problem with "lens shift" that you don't want.

Another solution may be some thin drafting tape for making lines, or even pin-striping tape from an automotive store. You can wrap just enought to act as a shim of the correct thickness to help center the lens in the opening. Worth a try if you can't get the correct board. Remember to use the tape properly, sticky side down. |-)

[Ted Harris]

amd then theere is the really simple, totally unscientific approach .... get the front element of thelens and shutter mroe or less lined up in the hole and start screwing the retaining ring on by hand .. use a fingerlanil if you need to the get it sorta tight .... then, holding the front element firmly where you want it tighten the retaining ring a bit more by hand .. not the spanner yet .... then, keeping the retaining ring from moving with your fingernail or one end of the psanner tighten the assembly by turning the front element of the lens/shutter combo untilthey feel tight ..... then, finally, at last take the spanner and give it one final tightening of the retaining ring ... ohyeah if you dont get the front element/shutter right where you wnat them on the next to last step you may find that your shutter speed and aperature dials are not exactly where you would like them to be but the lens willbe centered and tight.

[Michael S. Briggs]

The hole in the lensboard should be significantly wider than the threads -- normally the retaining ring has a projecting shoulder that is supposed to fit into the hole, so the hole needs a larger diameter than that of the threads on the shutter. The projecting shoulder functions as a light trap, making it less likely that some light will leak through the lens mounting area. Once you have screwed the retaining ring most of the way in, the projecting shoulder should fit into the hole and reduce the side-to-side play of the lens in the hole. If the projecting shoulder is missing, or if the shoulder isn't manuvered into the hole, the lens will have excess side-to-side play.

Past this, as Ted says, hold the lens in place and gently tighten before you do the final tightening with a spanner wrench. You could also try restricting movement of the lens with a piece of cardboard placed in the direction that the lens is moving when you tighten it, then remove the cardboard when you are done to restore the clearence. Position the cardboard so that the forces are on something fairly robust like the shutter body, and not concentrated on something delicate like one of the levers.

[Leonard Evens]

I agree with Michael Briggs and others that, most likely, the problem is that you haven't seated the shoulder of the retaining ring in the space between the lens and the board.

[Dan Fromm]

Leonard, Michael you're absolutely completely 100% right about why the hole in the board is slightly larger than the threaded tube at the rear of the shutter. Also about the purpose of the little raised flange at the front of the retaining ring.

But and however, without knowing the dimensions of the hole in Dietrich's recessed board all we're doing is discussing how the job should have been done. Dietrich, how big is the hole? And what shutter is the lens in?

I've had two problems with mounting lenses that are somewhat similar to Dietrich's.

First, putting an ex-Polaroid MP-4 Copal #1 Press shutter on a board. Polaroid's mounting standard for that lens is for a hole just big enough to accept the back of the shutter. There's no need for a centering flange on the Polaroid issue retaining ring, and there isn't one. So centering one of those on the board while using the retaining ring that came with it is a struggle.

Second, putting a shutter, any shutter, on one of those cheap reproduction Pacemaker Graphic boards. The <obscenity> who makes them uses sheet metal that's thinner than spec. As a result a retaining ring with centering flange can't clamp down on the board; the flange makes contact with the back of the shutter before the ring has clamped the board, so the lens will turn on it.

Cheers,

Dan

[Gem Singer]

Hi Dietrich.

Did you remove the small index screw from the back of the shutter? If not, this could be causing the shutter to be slightly tilted when you tighten it down, jamming the aperature ring. Simply remove the tiny screw if it is still there. It isn't really necessary with a recessed lensboard.

[Ole Tjugen]

Dietrich,

Even when mounted correctly, you'll find that the 90mm Angulon is very "fiddly" to use when mounted on a recessed board. I have one mounted on a flat board which works fine on my Linhof Color (you can't use much movements anyway), and a 120mm Angulon for my 5x7" Technika III - also flat board.

I have two Super Angulons (90mm and 121mm) on recessed boards. These have much larger image circles, so the recesed boards make it easier to use movements. But they're still very, very "fiddly".

Flat lensboards and Angulons work fine!

[jnantz]

dietrich:

i can not add much here, but i was wondering if can post images of the back threads of your shutter, the lensboard and the lens IN the lensboard with the threads sticking out of the hole.

maybe it is something that you and others (here) have overlooked. :)