View Full Version : safe to remove this screw?

24-Jan-2017, 16:44

I have a lens in a Synchro-Compur shutter and I want to mount it on a Linhof lens board. But I cannot lay the shutter flat on the board because of a screw that is sticking out of the back of the shutter. Can I remove the screw and proceed with the mounting? Or is the screw there for a crucial reason? The screw cannot be screwed any further into the shutter.

Please see the photo below.



24-Jan-2017, 16:52
You can remove the screw, however it is there to keep the lens from moving as you make adjustments. It is best, if you can, to drill a hole in the lens board to accommodate screw.

24-Jan-2017, 16:52
That screw prevents the lens from rotating on the lens board. Some lens boards have notches cut into the hole for this reason. You should cut this notch if your lens board does not have it. You can also remove the screw and store it safely. There is no other impact on performance.


24-Jan-2017, 16:53
Ok, thanks.

Bob Salomon
24-Jan-2017, 16:59
Remove it, Linhof did not use them.

Kevin Crisp
24-Jan-2017, 18:06
This must be the most frequently asked technical question.

Tin Can
24-Jan-2017, 18:17
This must be the most frequently asked technical question.

It's not obvious and we all know loose screws sink ships...

I first saw it, I wondered if it held something inside, that was very necessary, then I saw a lensboard and bingo.

24-Jan-2017, 18:17
The anti-rotation screw absolutely SHOULD be used.
Shutter makers didn't put these in just because they had extra screws.

It prevents the shutter from rotating when you cock it, in particular.
Left to its own devices, the shutter mounting ring will come loose if you use the shutter a lot.

If your lensboard doesn't already have a notch for that screw, you can cut one with a small file.
Note that the position of the notch controls the orientation of the shutter, so put it where you want.

- Leigh

Kevin Crisp
24-Jan-2017, 18:41
I was going to suggest the convertible front or back of the shutter question as the most asked but this little screw wins.

I've removed the screw on all my lenses. With the ring tightened with Mr. Grimes' wonderful wrench no cocking of the shutter is going to loosen the ring.

Keith Pitman
24-Jan-2017, 19:03
You don't need the screw if you tighten the retaining ring sufficiently. As a note, some lensboards have a "divot" in the rim for the screw, although it might not be where you want it.

24-Jan-2017, 19:10
... no cocking of the shutter is going to loosen the ring.
Mis-understanding here.

Operating torque is applied to the shutter, causing it to rotate.
The result of that rotation is that the retaining ring is no longer tight.

- Leigh

24-Jan-2017, 19:25
Fantastic responses!

Kevin Crisp
24-Jan-2017, 19:32
I understood perfectly well what you were saying. What I am saying is if you properly tighten the retaining ring, merely cocking the shutter isn't going to cause it to rotate. It won't move at all. It can't. The applied force from cocking is a small fraction of what it would take to loosen it by turning the shutter rather than the ring. If you have it just finger tight for some reason, yes, the shutter can sometimes come loose.

24-Jan-2017, 20:19
It won't move at all. It can't.
Hi Kevin,

And therein lie the falacy.

I certainly agree that it should not move when torque is applied.
That doesn't mean it cannot move.
I've encountered two shutters in my long shooting life that were loose.

Admittedly in the general case the anti-rotation screw is a "belt and suspenders" approach.
That's fine. My pants never fall down.

This is a safety feature, just like the ledge on the retaining ring that prevents damaging the shutter threads.
In a perfect world we should never have to worry about such damage occurring. The ledge guarantees that.

- Leigh

Kevin Crisp
24-Jan-2017, 20:31
The gentle push the shutter gets when the shutter spring is cocked (or, on a Copal, the aperture is opened or closed during composition) will not move a properly tightened shutter one micron. There is no fallacy.

Yes, if a shutter is loosely held by the retaining ring, it can move. So get a nice lens wrench like the Grimes one, properly tighten the retaining ring, and ditch the screw and you're done.

I'd even agree that if you are in a habit of loosely tightening your retaining rings, then you might want to go to all the trouble of drilling locating holes in your lens boards so you can use that little screw.