Rangefinder Calibration (at infinity)

[punkzter]

I recently sent two M6 cameras (a black and a silver) to Youxin Ye for a rangefinder adjustment. I had noticed that the cameras weren't aligning at infinity on a few of my lenses. If I remember correctly, the silver seemed worse, but I wanted to send both so that they would behave similarly. I have quite a few lenses, and infinity alignment wasn't the same across lenses or between cameras, which didn't give me any reference point.

I sent Youxin both M6s as well as a few lenses just to have him test for focus. He adjusted the black M6, said the silver was fine, and said that the lenses were all in focus.

Now that I have them back, I wanted to check them again for infinity alignment. And I'm having the same issue. The patch isn't perfectly aligned at infinity. It's not off by much, but you can tell that it's not aligned. The worst offending lens is a Summicron 50mm that Youxin said was in focus. I used the moon as my infinity target. I've also used a sign that is about 1.9 KM away.

I wrote to Youxin about this, and he didn't appear concerned, saying that film has more tolerance.

But I'm a little frustrated. It seems to me that an infinity check is a basic thing to do to make sure that the rangefinder is in alignment.

I guess my question is, is it common for different lenses to behave just a bit different when coupled? Am I expecting too much? I know that I won't be shooting wide open most of the time, and that film does have a bit more tolerance, but I'd rather start from correct alignment and then use the tolerance as an aid rather than a crutch for bad alignment.

Or, perhaps the camera is right, and it's just what I should expect from different lenses. I'd really appreciate any thoughts.

 

[Sonnar Brian]

This is where Rangefinder cameras and lenses can drive you crazy. I've found differences between cameras and lenses, all "in tolerance". I have certain lenses fine-tuned for the M Monochrom based on what Filter I am using. On Jupiter-3's, I've ground the mount down and moved the helical in on about 1 in 10 lenses.

Are the actual pictures in focus? Do some camera/lens combinations produce out of focus images?

 

[Chriscrawfordphoto]

I had the same issue with an M4-2 that DAG had worked on for me. I sent it back and he returned it in the same inaccurate condition and insisted that he was right because he has the Leitz tools to adjust it. Well, he was WRONG. The camera was off with every f--king lens I own, all of which focused perfectly on my other M-mount camera, an M3. I finally gave up on him and adjusted the damned thing myself and now all my lenses agree on both cameras and they focus perfectly.

 

[punkzter]

I might have to just break down and do some test images. The good news is that I haven't noticed anything in reality (though I haven't had a chance to re-test the black M6 which Youxin adjusted). In the past, if something isn't in focus, I just assumed that it was my fault. And generally I don't shoot open enough that depth of field wouldn't correct an error. So my images tend to come back in focus, or close enough.

So I suppose you could ask why I bothered asking the question 🙂 It does drive me crazy. I shouldn't hold onto any idea of "Leica" quality, but it does annoy me that a M body and a Summicron lens somehow shouldn't work together to align at infinity after being checked by a known tech.

I have limited time, so I've tried to avoid making test rolls. But maybe it's time to do one. Do you have any suggestions for distances to check? I suppose it would be wide-open and then try a few distances?

 

[Sonnar Brian]

Test the lens wide-open and at F4 at closest focus, and then again at 300ft/100m.

Focus shift due to spherical aberration and color filters with B&W probably exceed any errors in the RF/Lens combination. Best to check.

 

[Mark J]

I wound up adjusting my own years ago. All of my lenses focus the same. I check close focus by shooting a ruler at about a 45 degree angle with a pencil pointing to my point of focus. 4 bodies and 10+ lenses. The moon works good for infinity.

Mar J.

 

[Erik van Straten]

An M-Leica is easy to adapt to a lens, the reverse is much more difficult. On the bottom of the rangefinder-roller in the camera there is a big screw. Just turn this screw with a WELL fitting (slanted) screwdriver to adapt it to the infinity position of the lens. The steel wheel of the rangefinder of the camera is decentrally mounted. So NEVER adapt lenses to a camera, always adapt the camera to the lens.

Erik.

 

[ptpdprinter]

An M-Leica is easy to adapt to a lens, the reverse is much more difficult. On the bottom of the rangefinder-roller in the camera there is a big screw. Just turn this screw with a WELL fitting (slanted) screwdriver to adapt it to the infinity position of the lens. The steel wheel of the rangefinder of the camera is decentrally mounted. So NEVER adapt lenses to a camera, always adapt the camera to the lens.

What is the advantage of adapting a lens to Leica M body? The Leica M body's raison d'etre is its rangefinder. As I understand it, you can't use the rangefinder with an adapted lens. If you have a special lens that you want to use, why not get a matching body for it and at least you won't have to guess focus?

 

[Erik van Straten]

What is the advantage of adapting a lens to Leica M body? The Leica M body's raison d'etre is its rangefinder. If you have a lens that you want to use, get the matching body for it and at least you won't have to guess focus.

Yes, that is what I've said. Most Leica-users have only one M-Leica. Get yourself a slanted screwdriver (or make one yourself) that fits the big screw on the downside of the roller (the wheel that touches the lens, it is decentrally mounted) of the rangefinder. If the rangefinder/lens combination doesn't reach infinity, simply turn the big screw until the rangefinder and the lens do match when set at infinity.

Erik.

 

[hap]

An M-Leica is easy to adapt to a lens, the reverse is much more difficult. On the bottom of the rangefinder-roller in the camera there is a big screw. Just turn this screw with a WELL fitting (slanted) screwdriver to adapt it to the infinity position of the lens. The steel wheel of the rangefinder of the camera is decentrally mounted. So NEVER adapt lenses to a camera, always adapt the camera to the lens.

Erik.

I am not criticizing ( I do not have the knowledge or skills in this space) . However, it seems the opposite of what Brian has been doing for decades. No?

 

[Sonnar Brian]

I have over 120 lenses in Leica mount. Probably half required adjusting. Different manufacturers make different assumptions about film sitting in a camera, or optimize the focus of the lens for stop down use. A 5cm F1.5 Summarit is optimized for F2.8. Mine- optimized for F1.5 because I changed the spacing of the rear group. Same with shims, some manufacturers optimize for stop-down, I set them for wide-open, On the M Monochrom- lenses that have a lot of focus shift due to chromatic aberration- I optimize for a deep yellow filter. Most of my lenses were made well before the digital age, many before computers were used to compute a lens- let alone be used on a digital camera.

 

[Erik van Straten]

I do not say anything against Brian, he is a great mechanic. I just want to warn the people who want to file down the focus curve of their new Noctilux if the focus is incorrect at infinity. In that case, it is better to use the eccentric screw located on the underside of the roller. If the focus then is still not correct (e.g. for close-ups) take the camera and the lens to a professional Leica repairman. In addition to the eccentric screw in the roller, there are more options for adjusting the rangefinder. The rangefinder of an M-Leica is a refined instrument with many adjustment options.

Erik.

 

[Sonnar Brian]

I do not say anything against Brian, he is a great mechanic. I just want to warn the people who want to file down the focus curve of their new Noctilux if the focus is incorrect at infinity. In that case, it is better to use the eccentric screw located on the underside of the roller. If the focus then is still not correct (e.g. for close-ups) take the camera and the lens to a professional Leica repairman. In addition to the eccentric screw in the roller, there are more options for adjusting the rangefinder. The rangefinder of an M-Leica is a refined instrument with many adjustment options.

Erik.

Thankyou Erik- I've had some great optical mechanical engineers work for me- maybe some of that rubbed off on me! "How many Fortran Programmers does it take to screw a lens into a Leica?"

I would not suggest that anyone try taking apart and adjusting an expensive lens without having the proper tools and experience. If adjusting your Leica and other rangefinders, be sure to have the correct tools. I learned that the hard way decades ago.

 

[Jonathan R]

I don't want to hijack this thread, but I think this is relevant ... When the M8 came out, wasn't it necessary to adjust lenses to focus on its sensor, which was positioned at a slightly different distance from the lens mount compared with the film plane of analogue Ms?

I ask this because I have two lenses, a pre-digital Summicron 50mm, and a later Summicron 35mm ASPH which I think would have been made around the time of the M8. When the 35mm lens is at infinity, the rangefinder images don't quite marry up. They marry up perfectly with the 50, as they always have. It seems to me that in this situation - which is similar to that of the OP - the only option is to adjust the 35mm lens, contrary to what Erik advocates. If the camera was adjusted it would spoil things for the 50mm lens, surely?

I will add that I tolerate the small disparity with the 35mm lens, although my eye can't help noticing, and it does niggle. But in practice both lenses are capable of very sharp imaging at all distances.

 

[Erik van Straten]

I have two lenses, a pre-digital Summicron 50mm, and a later Summicron 35mm ASPH which I think would have been made around the time of the M8. When the 35mm lens is at infinity, the rangefinder images don't quite marry up.

The 35mm has a larger dept of field, so the 50mm needs a more precise rangefinder. If you notice in practice that the distance meter does not indicate the correct distance, I would consult a specialist. Just make some test shots with the camera fixed on a tripod to see what's going on.

Erik.

 

[Erik van Straten]

If adjusting your Leica and other rangefinders, be sure to have the correct tools.

To adjust the rangefinders of my M's I have a special screwdriver with a slanted head that fits the slot of the eccentric screw exactly. A normal screwdriver can damage this screw. I needed it recently to adjust the rangefinder of my MP for my new Heliar Classic 50mm f1.5 on infinity.

This subject is not in the user manual of the Leica AFAIK, so it is good to repeat it a few times here.

At full aperture the lens/camera-combination now focuses perfectly, even on a big distance, see picture.

gelatin silver print (heliar classic 50mm f1.5) leica mp

Erik.

 

[Jonathan R]

To adjust the rangefinders of my M's I have a special screwdriver with a slanted head that fits the slot of the eccentric screw exactly. A normal screwdriver can damage this screw. I needed it recently to adjust the rangefinder of my MP for my new Heliar Classic 50mm f1.5 on infinity.

This subject is not in the user manual of the Leica AFAIK, so it is good to repeat it a few times here.

At full aperture the lens/camera-combination focuses perfectly, even on a big distance, see picture.

gelatin silver print (heliar classic 50mm f1.5) leica mp

Erik.

So Erik, just to be clear, are you saying that you dedicate a camera body to one particular lens by adjusting the rangefinder? And after making that adjustment that camera body may or may not suit other lenses?

 

[TenEleven]

So Erik, just to be clear, are you saying that you dedicate a camera body to one particular lens by adjusting the rangefinder? And after making that adjustment that camera body may or may not suit other lenses?

There's more to that. I find the infinity spot where infinity is displayed as "bang-on" to be quite "soft" on my M2 and M4 film Leicas. Meaning there's some leeway either way before it displays something as not in focus at infinity for a sufficiently far-away target. Therefore with Eriks method, I can chose an interim setting that will display infinity correctly with most (not all, my collection like Brians is too big) lenses.

There is a non destructive way to adjust the lenses, if and only if they are short of infinity on the RF which I will detail here:
Get some women's nail-color "top hard coat" or "varnish". Mine is called "topcoat" - it is clear. No color. Your wife may have it. It is clear and dries quite flat and very hard. It sticks well to brass and aluminum in my experience. Gently apply a very thin(!) it only takes very little(!) layer to the spot where the infinity position is on the lens cam, or if you want to adjust the whole range the whole cam. I've done either or depending on the lens and its focus behavior.

Then check with the camera again. If it's still off apply another layer etc.

I have used such-treated lenses for 2 years now and haven't had any problems with the nail "top hard coat" coming off.
If and only if you want to remove it I'd advise against acetone (as it may dissolve some of the lens painted on blacking) and just use your fingernail to scrape it off. As it's on there quite good it will take some force but you can scrape it off still. It usually comes off in nice big flakes which you can then pick off to reset the lens to "factory".

Edit: Basically I want to second Eriks warning of "don't file your lenses, please" you'll make future collectors (like me, or yourself) sad later on. If the lens is truly over infinity even with the help outlined above - get some different M/L adapters - some are thicker which can help you bring that back in also.

 

[Erik van Straten]

So Erik, just to be clear, are you saying that you dedicate a camera body to one particular lens by adjusting the rangefinder? And after making that adjustment that camera body may or may not suit other lenses?

Yes, the rangefinder can only be optimized for one lens, usually no problem because most people with an M-Leica only have a limited number of lenses. Wide-angle lenses have no problems at all, because those lenses have a greater depth of field. I recommend adapting the rangefinder to the most commonly used lens. Most Leitz and Leica lenses are precisely adjusted, unless they are lenses that someone has been filing who didn't know their rangefinder was set up incorrectly.

Erik.

 

[Sarcophilus Harrisii]

The only way to definitively know what is going on with your camera body/lens/rangefinder is to verify your base line reference, then inspect the calibrations.

If you're dealing with a fixed lens camera things are a bit simpler. You adjust the focus stop/shims/optics relative to helicals, and dial the rangefinder in to match. Job done.

Not so easy for an interchangeable lens system camera. It's meant to work for any lenses for that system (assuming they're in good repair and adjustment). How to do?

The key, of course, is the lens register (aka back focus) of the body. If it's to spec, correctly adjusted lenses should return sharp infinity focus at the film gate.

If your back focus is right and your lens isn't sharp, by definition the problem is the lens.

If the lens is good but the RF does not match then, it depends. In theory the RF is off; but what if the lens or its cam have been messed with? You could chase your tail.

Best if possible to check rangefinder with a known good standard lens. By "known good", meaning, not only one that hits infinity focus correctly, but drives a well adjusted RF to a sharp merge, at same distance.

Easiest way to accurately verify back focus without access to a camera specific autocollimator is with surface plate and height gauge, or dial gauge and stand. If register correct, and lens mount and film rails parallel, a mis-focusing lens by definition, will itself be at fault.

Correcting these points is another matter obviously, dictating the visual acuity, experience, equipment and skills to use same. But, the above workflow will enable a person with the requisite ground glasses and loupes to positively ascertain if any calibration faults exist; and if so, where they lie.