Greetings [all]

There is a small buttom attached on the lenses barrel of the Nikkor 105 f/2.8 micro, movable over a small piece of silver metal, this being screwed right on the focusing ring surface. So far no one here in Rio de Janeiro/BR has been able to tell me what's it for. I also found no tracking of it through literature. So, would some of you know what's it for?

Thank you in advance.

Regards

W. daSilva

-- W. daSilva (walzi@niteroi.etc.br), July 01, 2001

Answers

W.

I have this lens. The screw allows you to lock focus when the lens is in a vertical or near vertical position. I have not found it to be necessary because the helicoil focus provides ample resistance; furthermore, the focus-lock screw on my lens does not firmly lock the barrel into a given position - it just increases the focusing mechanism's resistance.

Eric

-- Eric James (eajames@u.washington.edu), July 01, 2001.

Dear Eric,

Thank you for your reply.

Indeed I believe there would be no other use for this buttom if not the resistance control. However in the particular lenses I own, the buttom can perform an entire turn - either screwing all clockwise or all counterclockwise - yet moving itself alone; there seems to be no perceptible transmission of its mechanical input to another piece of hardware (it would help me a lot if you could kindly check if you have the same feeling with your lenses buttom). Moreover, the resistance of the focusing ring remains constant and very high no matter where the buttom stops or how the lenses are inclined. The resistance is at least a lot higher than that of any of my other lenses. Mine seems to be stuck at the maximum resistance point, then. Repair should be required.

Regards,

Walzi

-- W. daSilva (walzi@niteroi.etc.br), July 02, 2001.

Walzi,

First off, I think that the resistance to focusing on my lens is slightly greater than any of my other Nikkor lenses (when the tightening screw is all the way counterclockwise). Second, you mentioned that the screw on your lens will make an "entire" turn. Do you mean only 360 degrees? On my lens this screw will make greater than 3 full 360-degree turns. If yours will only make a single full rotation I would recommend applying a bit more torque in the counterclockwise position (perhaps the screw is stuck). I'm sorry that I can't offer any more help - perhaps these tightening screws are problematic; as I mentioned earlier mine won't tighten enough to completely lock the focusing mechanism.

Good Luck!

Eric

-- Eric James (eajames@u.washington.edu), July 02, 2001.