Name 'em Screws: RF Calibration Related Topic

[danop]

Hi everyone,

 

It seems one of my M's rangefinding unit is beyond the help of a simple infinity reset.

I have read many posts and articles on DIY RF adjustments and have decided to give it a try. I believe my

overshot focusing problem has something to do with the length of the arm that holds the eccentric drum.

 

1) But before proceeding with any adjustment, will anyone be so kind as to name these screws, their

functions, and the effects I'd get should I turn them clock and counter clock wise?

 

2) Any tips, tricks, or pitfalls anyone may have regarding rangefinder calibration will be most appreciated.

 

3) Also, is there any way I can reliably test the accuracy of the RF unit on site without having to unload the

film and perform a ground glass check? Infinity check doesn't always guarantee a close focus accuracy.

 

Rangefinder calibration should be a simple user serviceable process, provided many Leica users are out

working in remote areas for an extended period of time.

 

Thank you so much,

Regards,

Danop<div></div>

[guy bennett]

Re: #2, try <http://nemeng.com/leica/034b.shtml>here</a>.

 

Good luck!

[guy bennett]

Sorry! That was a failed attempt to include a hyperlink in the message rather than just give the address, which I'll do here:

 

http://nemeng.com/leica/034b.shtml

[john_shriver]

Pointless to do anything unless you can also check collimation of the lens and camera. If the flange-film distance is off, no amount of adjusting the rangefinder can make anything right. Same thing if the lens isn't collimated at infinity.

[carlo_innocenti]

Screw A: its axis does not coincide with the axis of the roller. By turning this screw, an offset displacement is introduced which is almost the same at any subject distance.

 

Screw B: allows the rangefinder arm to be changed in length. Screw B allows the selection of the gain in the coupling of the lens to the camera body.

 

Screw C: after having adjusted screws A and B, screw C allows the rangefinder arm to be firmly held in place between an (eccentric) spacer disc and the cam of the lens, provided that the lens is focused at infinity. If screw C is properly adjusted and the lens is set at infinity, any bouncing of the rangefinder mechanism inside the camera body is prevented, even in case of camera body acceleration.

 

Note: the adjustments of screws A and B somehow affect each other. If your rangefinder arm seems the have a wrong length, try rotating screw A before touching screw B. this is because there are two positions for screw A that allow collimation at infinity, but the length of the rangefinder arm is not exactly the same for these two positions.

 

I hope this will be helpful.

 

Regards,

 

Carlo

[dan flanders]

I am a confirmed DIY addict but one thing I stay away from is fooling with the RF follower arm or any other internal 'body' element. Leave that to the experts and look elsewhere for things you can fix without screwing up the whole works. If the focusing mount has been disassembled the helicoids may be off a thread or two. This is the most common problem with lenses of unknown provenance. Look for dirt or lint in places that might affect focus -- on the back of the flange or in the bayonet recesses. My step-dad had a sign over his work bench, "Only damn fools and watchmakers take the backs off watches!" -- The same applies to Leicas and other fine gear!

[john_shriver]

If you want a camera whose focus accuracy can easily be corrected in the field, get an SLR. All that is required in an SLR is that the "ground glass" be the same distance from the lens as the film is. Only one adjustment.

 

There's like six or seven adjustments that have to be right on the Leica rangefinder system, between the camera and lens. OK, some of them are not likely to go bad in the field, like swapping lens heads between different barrels (focal length mismatch).

[dan flanders]

In over sixty years experience with Leicas I have never had any issues that required anything more than a bit of vertical alignment. I've had the ground glass of several Nikons and Cannons get loose and foul up the focusing, and they are a bugger to fix. I haven't had any focusing problems with Rolleis or other TLR's. Obviously, out of the multitude of any brands in circulation, you only hear about the failures -- the successes are taken for granted and rarely reported!

[danop]

Guy -> Thank you so much for the link. That was among some I have gone through prior

to writing this post.

 

Carlo -> Wow! So that's what Screw C does! Thank you very much! Your tips are also more

helpful than you would know.

 

John -> You are probably right about SLRs and their WYSIWYG nature, that's why I'm

keeping my Nikon FE2 with me as a backup. It's one camera I have never had any problem

with.

 

Of all the superior lenses Leica has, it's such a shame that my shots should be impaired by

malfunctioning of some finder's mechanism that I have no means of seeing (and

foreseeing.) What good is my Leica if I can't trust its rangefinder patch?

 

Dan -> Wow, you are lucky! Perhaps it depends on how you treat your camera.

I treat mine rather well (and my wife envies them) but still, I have constant problems with

their RF units.

 

While the ground glass in my FE2 proves to be quite stable, the one in my F4 seemed to

trip out of place from time to time much like you had mentioned, yet technicians can't

seem to find anything wrong with the camera.

 

Excellent tips and warnings! Thank you so very much!