Leica IIIa Rangefinder Alignment

[Fragomeni]

Hi all. I'm working on aligning a Leica IIIa's rangefinder but I'm having trouble. It gets very close but always seems to be just slightly off vertically. I now both access points for the rangefinder on this camera and the lateral adjustment is working fine but the verticle adjustment doesn't seem to have much affect. I can't figure it out. Any help would be appreciated. Maybe there is a specific procedure for putting both vertical and lateral in proper alignment that someone can share with me. Thank you for the help!

[David Lyga]

Every rangefinder I ever worked on had two distinct screws for alignment. I never worked on a Leica (cannot afford!!!) but I have done this on the Canon Q series and others.

Under the top cover, near the viewfinder mirror (45 degree angle) there are screws to do this. Sorry, I cannot be more specific because different cameras have slightly different placements.

What you need to do FIRST is find out where true infinify is. You do this by shooting maybe 5 frames (at a detailed 'infinity' object, maybe a mile away) turning your focus knob at slight, measured positions from, say, 25 feet to the marked 'infinity', AT WIDE OPEN APERTURE to limit depth of field. You process the negs and determine which is sharpest. Now you know where TRUE infinity is and you mark the lens scale to indicate this.


Now you must align your RF to indicate that this position is, indeed, true infinity and you do that with the two screws I started out with. When this is done you can say that you finally have an accurate rangefinder. Few people ever question the alignment but I do this all the time, especially with SLRs. The mirror is not always perfectly at the correct height. Some SLRs have a convenient set screw under the front of the mirror (Fuji ST series, Zenit series) but sometimes I have to slightly bend the prong that the mirror rests upon. You might have to either raise or lower the mirror depending upon how different true focus is from apparent focus.


The bottom line is this: you MUST find out where TRUE infinity is and THEN mark the lens at that precise point on the focus scale. Only then can you adjust the SLR mirror to MATCH what you now know. It is amazing the blood that can be drawn out of these 'cheap' lenses to reveal such stunning, cutting sharpness.

Proof: just place a tiny piece of scrap film carefully under the front your SLR mirror at the place where it rests and then focus at infinity and see how different your focus is compared with focussing with nothing underneath the front of the mirror. That mirror MUST be at a truly critical height. - David Lyga

[John Koehrer]

The vertical adjustment is an optical wedge located in the window closest to the lens. The adjustment is rotational.
According to the Tomosoy book the chrome ring around the lens is removed for access to the adjustment.

[Fragomeni]

Every rangefinder I ever worked on had two distinct...

Hi David, thanks for the information but adjusting a Leica IIIa is a bit different. The issue I'm having is not with finding infinity, it is with the vertical rangefinder adjustment apparently not working properly. The Leica IIIa rangefinder is not adjusted via two screws like most modern design rangefinder cameras are. The lateral adjustment is achieved via a setting screw under a cosmetic screw in the face of the top plate next to the viewfinder window while the vertical adjustment is achieved by rotating an optical wedge as John described below your post. The problem is that rotating this optical wedge is not properly adjusting the vertical alignment.

The vertical adjustment is an optical wedge located in the window closest to the lens. The adjustment is rotational.
According to the Tomosoy book the chrome ring around the lens is removed for access to the adjustment.

John, Thaks for the reply. I know that the optical wedge is supposed to rotate and adjust the vertical but it isn't working. That is the problem. I've rotated it but it never seems to bring it up all the way to perfect alignment. My only guess is that at soem point the camera must have been jarred and a mirror shifted or soemthing. I may just send it off at some point since it would be good to have a full CLA done anyway. It just would have been nice to have gotten the rangefinder fully functioning without having to send out and shell out cash.