DIY rangefinder adjustment
Use any M rangefinder camera body for a while and you will notice the rangefinder patch has a tendency to drift out of vertical and infinity (ie horizontal) alignment. Can you fix this yourself?…
Horizontal RF Adjustment
In June 2002 John Collier noted the following instructions on how to adjust the RF patch alignment when at infinity:
This is very easy to do.
The roller on the end of the rangefinder coupling arm is held on with an eccentric screw. First get a screwdriver that fits exactly and when making the adjustment ONLY apply turning force. DO NOT PUSH AGAINST THE RANGEFINDER ARM. Sorry for yelling but it is important.
Now turn the screw slightly in any direction and check the camera again. Has it gotten better or worse? Now you know which direction you need to turn the screw. Now keep tweaking it slightly until everything lines up correctly at infinity.
As others have pointed out, infinity is a long way away. At least three kilometers but preferably farther if you can. I often use the moon at night. It is rather far away and there is great contrast between it and the night sky. This makes checking the adjustment easy.
The eccentric screw holding the roller gives the rangefinder a fixed starting point. It "zeros" the rangefinder so to speak. The eccentric pivot adjusts the relationship between arm movement and shaft rotation so you can fine tune the focusing accuracy between infinity and close focus. You need a set starting point to be able to: quickly and properly evaluate the rangefinder accuracy, easily see if it needs further adjustment and in what direction.
A Leica tech first adjusts infinity at the roller and then checks it at 10 metres and 1 metre. Most of the time that is all that is needed as once the arm length is properly set, it seldom needs readjustment […]
Vertical RF Alignment
The ability to DIY depends on what model M you have. If it is a M3, M2, M4, M5, M4-2 and early M4-P then yes, you can easily recalibrate the RF patch vertical adjustment yourself. Just just remove the small cover screw on the camera face plate — the one between the RF windows immediately above the lens mount (ah, so that's what that screw does!) — and then while looking through the viewfinder, reach into the opening you just made and turn the small recessed adjustment screw within. You don't have to pop the top off the camera body, you don't have to pull anything apart, just look through the viewfinder and gently turn the VF alignment screw in the hole on the front body until the patch vertical alignment snaps into place. Easy.
You can find photographs showing you how to do this at the following www site: <mediajoy.com/en/lrc/>.
If however you have a late-run M4-P or M6 or later model, then you need to use a special RF adjustment tool. In the case of post M6 models, you also have to remove the Leica red dot logo above the lens mount to uncover the recessed adjustment "screw".
Yes this is a nuisance and was deliberately introduced by Leica to stop weekend warriors from doing their own adjustments. You cannot use any old screw driver or torx tool to do the adjustment either, only a special tool Leica make and supply — "Adj. RF M4P, M6" #1500-0000-1279 — for approx $US 250 (ouch).
For those who want more detail on the vertical and horizontal adjustments, here's some more information from Mr Collier:
[…] The most common rangefinder adjustments are:
1. the rangefinder distance calibration, comprising infinity and close focus adjustments, and
2. the rangefinder vertical alignment.
All these adjustments can be done without the top plate coming off.
The vertical alignment is adjusted through the "red dot" on cameras equipped with it, otherwise through the cover screw located directly above the lens mount. In the early cameras, it is a simple adjusting screw but on the later cameras (M4-2 and up) it is an eccentric cam that requires a special tool.
The rangefinder distance calibration is done by the eccentric pivot of the rangefinder arm and the eccentric mounting screw of the rangefinder arm roller. The roller position determines the starting point of the rangefinder arm travel (infinity) and the eccentric pivot adjusts the ratio of rangefinder movement to lens cam movement by varying the length of the arm. A shorter arm gives you a larger movement of the rangefinder pivot for a specific amount of lens cam movement; and, a longer arm gives you less movement of the rangefinder pivot for a specific amount of lens cam movement. Simple! There are also rangefinder travel stops but we hardly have to go into that now.
Now that is what Leica will sometimes do at a Leica clinic and would be considered a minor adjustment. It would take a technician about half an hour to perform. There are however other rangefinder adjustments which require the top plate to come off to perform.
All three brightline frame sets have separate adjustments so that they are in the correct position at infinity and close focus. The mechanism that selects between each mask set when a lens is mounted is of course adjustable as well. I could go on, but all this stuff is beyond most people's ability (certainly mine) and useful only for repair technicians.
[…] For most regularly serviced cameras only minor adjustments are required and you do not need to take off the top plate unless there is a problem with the brightline mechanism. On an older camera with suspect or no maintenance records, it is better to take off the top plate and check, clean and lubricate everything, adjusting where necessary.
Hmmm, sounds like an amusing way to kill a few spare hours. If you want to get into this more deeply, then click here ( 7k bytes) to read a 7000 word text document on the ins and outs of DIY RF adjustment. Be warned, it isn't something for the impatient or shaky handed.
In a hurry? Use your fist!
Although Mr Collier appears to take great care with getting RF adjustments right, sometimes even he can resort to shortcuts. Read his June 2003 post at <LUG - v25/msg00324.html>, where he kept thumping the camera against the palm of his hand until the RF alignment returned to "normal"(!)
Rangefinder prism too dim?
Got an ancient M or LTM and think it's time to get the rangefinder prism re-silvered as it has grown too dark to focus accurately? You may be in luck! Usually you don't need to re-silver at all, but merely have the decades of grime cleaned off the RF prism. See the June 1996 experiences of Michael Bell at <LUG - v00/msg03227.html>