Focus calibration

[Vagabond1031]

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Hi,

Can someone point me to some reputable reference or thread that can help with this topic?

I have the M262. I’ve noticed it has been back focusing for some time on both my 35mm Summicron and 40mm Voigtlander. Did some digging and tried calibrating it by focusing on infinity and adjusting the “nut” in the camera with a 2mm hex key. 

Once infinity has been calibrated, I did a a test on 1m, 2m and 3m focusing. It seems 1m and 2m are slightly off with F5.6. After recalibrating for 1 and 2m, infinity is very obviously off. This happens on both of my lenses. 

Does anyone have an idea what I’m doing wrong? 

 

Thanks

 

Edited January 26 by Vagabond1031

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[charlesphoto99]

There are two adjustment screws - the hex infinity one, and also one at the point where the arm attaches (use to be a slot edge but now on my M10-R a Philips, so not sure with the 240). That screw positions where the arm starts in relation to infinity and .7M, the hex on the roller where it stops at infinity. You need to find the balance between the two. It can be a long and frustrating process doing it yourself, but it can be done. Micro adjustments on both! And youmonly need to loosen the inner screw so it nudges a bit. Don't loosen too much! I know if you search around you can find some diagrams of which way to turn which direction for adjustment. Or do some trial and error and make your own (good idea to write down anyway which way you turned each as you will get confused quickly going back and forth). Best to find correct focus at around 5m and infinity if I recall correctly. Calibrate wide open (note some Leica 35's can have focus shift in the mid apertures). Personally I don't do mine anymore. Last time I tried to do the vertical on my M10M (via the cap at the front) I got the cap screwed back on wrong and it's now stuck (and the vertical is still slightly off). 

Found the thread: 

 

[Vanillasludge]

4 hours ago, Vagabond1031 said:

Hi,

Can someone point me to some reputable reference or thread that can help with this topic?

I have the M262. I’ve noticed it has been back focusing for some time on both my 35mm Summicron and 40mm Voigtlander. Did some digging and tried calibrating it by focusing on infinity and adjusting the “nut” in the camera with a 2mm hex key. 

Once infinity has been calibrated, I did a a test on 1m, 2m and 3m focusing. It seems 1m and 2m are slightly off with F5.6. After recalibrating for 1 and 2m, infinity is very obviously off. This happens on both of my lenses. 

Does anyone have an idea what I’m doing wrong? 

 

Thanks

 

Can I ask which Summicron variant you have?   Unless it’s an asph, the lens, and the 40mm are prone to focus shift, making exact calibration a moving target.  The V4 shifts quite substantially between f2 and f4. 

 

 

[Jean-Michel]

See the diagram, it os from a post a few years ago.

For infinity, you do need to focus on something very far, at least 1 km

 

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[Vagabond1031]

5 hours ago, Vanillasludge said:

Can I ask which Summicron variant you have?   Unless it’s an asph, the lens, and the 40mm are prone to focus shift, making exact calibration a moving target.  The V4 shifts quite substantially between f2 and f4. 

 

 

I have the asph v2 I think. Serial number search returns unknown but for sure it's asp and the 6-bit version.

 

[Vagabond1031]

@charlesphoto99@Jean-Michel

 

You guys rock! I've spent hours searching on Google and youtube. Should have come to this forum to start!

I'll check out if my m262 has the extra philips screw, that might be it. I was also focusing on a building maybe 400m instead of 1K. I didn't think it mattered in terms of "infinity". Let me give those a try.

Thank you!!

Edited January 27 by Vagabond1031

[Vagabond1031]

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Giving an update:

Indeed, I see the extra philips screw to adjust the arm throw. I am missing a small flathead philips driver to adjust it. Will have to get one before continuing. 

However, having read your help here and the original tutorial, I feel much more confident in what should be done!

Again, thanks so much for this 🙏. I had thought of selling my M262 and summicron 35mm for Q3 43 partly because I want to shoot on 40-43mm, needs better control on framing and tired of not knowing what's going on with the focus. I may think otherwise now 😉

[pippy]

2 hours ago, Vagabond1031 said:

...I had thought of selling my M262 and summicron 35mm for Q3 43 partly because I want to shoot on 40-43mm...

Just FWIW...

In order to make the 40mm f1.4 Nokton both physically very compact and with a fast maximum aperture there is a trade-off whereby when used close-up and at certain apertures there will be some amount of focus-shift; it is unavoidable.

In a nutshell (having done quite comprehensive tests myself) when used at min. focus and max. aperture the focus should be spot-on. Stopping down to f2.0 / f2.8 there will be noticeable shift. Things start to improve at f4.0 and by f5.6 the increased depth-of-field is (usually) sufficient to make images acceptable.

At slightly greater distances, as might be expected, the effect of focus-shift is reduced and images captured using apertures faster than f5.6 are more useable. By the time subject-matter is a handful of metres away there should be no noticeable problems at any aperture.

As a general rule-of-thumb when taking photographs at min. focus either shoot wide-open or stop down to f5.6.

Philip.

Edited January 27 by pippy

[Vagabond1031]

14 hours ago, pippy said:

Just FWIW...

In order to make the 40mm f1.4 Nokton both physically very compact and with a fast maximum aperture there is a trade-off whereby when used close-up and at certain apertures there will be some amount of focus-shift; it is unavoidable.

In a nutshell (having done quite comprehensive tests myself) when used at min. focus and max. aperture the focus should be spot-on. Stopping down to f2.0 / f2.8 there will be noticeable shift. Things start to improve at f4.0 and by f5.6 the increased depth-of-field is (usually) sufficient to make images acceptable.

At slightly greater distances, as might be expected, the effect of focus-shift is reduced and images captured using apertures faster than f5.6 are more useable. By the time subject-matter is a handful of metres away there should be no noticeable problems at any aperture.

As a general rule-of-thumb when taking photographs at min. focus either shoot wide-open or stop down to f5.6.

Philip.

Thx for going through the testing @pippy Glad you did this. I would have thought at min. focus to best avoid wide-open with this lens. I'll keep this in mind if I keep the lens. You have any experience with the Minolta 40mm f2? I'm thinking of getting that instead. Mainly for a more vintage aesthetics and that the 1.4 Nokton's focus is stiff at certain points of the throw. I've heard because of the mount, the focus is a slight bit off on digital M. Or not worth the switch?

[pippy]

8 hours ago, Vagabond1031 said:

...I would have thought at min. focus to best avoid wide-open with this lens......You have any experience with the Minolta 40mm f2? I'm thinking of getting that instead. Mainly for a more vintage aesthetics and that the 1.4 Nokton's focus is stiff at certain points of the throw. I've heard because of the mount, the focus is a slight bit off on digital M. Or not worth the switch?

Taking these points in order;

It might at first sound strange but, in fact, being sharp at min. focus and max. ap. makes perfect sense. When shooting right up close depth-of-field will not help bring subject matter into focus therefore focus is set accurately for f1.4. As subject-matter goes further and further away from that position focus inaccuracy becomes slightly less critical. Additionally there is usually less need to use f1.4 when the s-matter is further from the photographer. By way of example how often do photographers need to use f1.4 when shooting landscapes?

I have no personal experience with the 40mm Summicron / Rokkor but from what I've read it will share many of the same characteristics of the 35mm Summicron of the time as it used, essentially, the same optical design (6 element in four groups double-gauss) which was slightly re-calculated to give the 40mm focal length;

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As such there WILL still be the same focus-shift phenomenon although, as the lens is f2.0 rather than f1.4, the effect will be less pronounced.

In terms of 'Vintage Aesthetics' the Nokton is superb. It is, as has been discussed many times, in essence a reworked 35mm v1 / v2 Sumillux and, at f1.4, shares many of the same optical aberrations which has endeared these old Summilux lenses to present-day snappers. Summilux to the left, Nokton on the right;

The 40mm f2.0 - whether Summicron or Rokkor made - will exhibit traits of the v2 / v3 35mm Summicron. The Nokton, similarly, renders in much the same fashion as the Summilux. It follows that all of these lenses could accurately be described as having 'Vintage Rendering'.

From my own experience with a 1974 v2 Summilux, an LLL '8 Element' (35mm v2 Summicron clone) and the Nokton I can say that from c. f2.8 down they all render in almost an identical fashion. It is highly unlikely(*) that anyone looking at photographic prints of images taken with these lenses in this aperture range could tell which snap was taken on which lens. All three lenses are very sharp when stopped-down; it is only when they are used at - or near - max. ap. that they show their 'vintage' character to the full. If this 'vintage' look is what is desired, then the way they render when used wide open should be a major determining factor.

If your Nokton has "stiff" focussing there is something wrong with your copy. These lenses are frequently noted for the smoothness of their focussing action.

The accuracy of the 40mm Summicron / Rokkor lenses has been raised in the forum a few times. From what I remember - and I might well be mistaken! - the issue is to do with the profile (i.e. slope) of the rangefinder-cam part of the mounting flange. These lenses were designed to be used with the Leica CL / Minolta CLE cameras of the 1970's. Being shorter than the M cameras the viewfinder and rangefinder windows are closer together than those of the M cameras which means that they have a correspondingly shorter rangefinder base. IIRC it is because of the different cam-shape which was neccessary for use with these shorter bodies that there may be issues but, again, how much of an issue this might be in actual use may depend on one's shooting preferences / typical subject-matter.

It might be worth doing a 'Forum Search' on this topic? Otherwise you might consider starting a new thread on the subject in the Leica M sub-forum as many forumites have these lenses and will be able to offer views based on experience gathered through actually using them.

Whether it might be worth a switch? Only you, I'm sorry happy to say, can be the judge. I'm fortunate enough to have lenses which cover all these bases but if I had to choose between the Nokton and a 40mm Summicron?.....I'd probably keep the Nokton. It has a really beautiful quality (IMO) when used wide-open - which the f2.0 lenses can't match - and is tack-sharp when stopped-down so the advantage of its rendering at f1.4 would most likely be the deciding factor for me.

Best of good fortune sorting out your own decision!

Philip.

* There are some circumstances where the optical aberrations of the Summilux might give the game away but that's another story for another time!...😸...

P.S. Do you like to use filters? If so be advised that the 40mm f2.0 lenses have an unusual thread pitch and filters / lenshoods are pretty much unique to these models. The UVa apart filters for use with the Summicron / Rokkor are scarcely to be found.

Edited January 28 by pippy
Adding a P.S.

[Ray Vonn]

1 hour ago, pippy said:

If your Nokton has "stiff" focussing there is something wrong with your copy. These lenses are frequently noted for the smoothness of their focussing action.

Thanks for pointing this out, the original comment did raise an eyebrow as the focusing action, at least on my copy, is practically perfect;  I'd assumed it was the same with all copies unless as you suggest, something is wrong with the lens.

[Vagabond1031]

On 1/28/2025 at 6:35 PM, pippy said:

Taking these points in order;

It might at first sound strange but, in fact, being sharp at min. focus and max. ap. makes perfect sense. When shooting right up close depth-of-field will not help bring subject matter into focus therefore focus is set accurately for f1.4. As subject-matter goes further and further away from that position focus inaccuracy becomes slightly less critical. Additionally there is usually less need to use f1.4 when the s-matter is further from the photographer. By way of example how often do photographers need to use f1.4 when shooting landscapes?

I have no personal experience with the 40mm Summicron / Rokkor but from what I've read it will share many of the same characteristics of the 35mm Summicron of the time as it used, essentially, the same optical design (6 element in four groups double-gauss) which was slightly re-calculated to give the 40mm focal length;

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

As such there WILL still be the same focus-shift phenomenon although, as the lens is f2.0 rather than f1.4, the effect will be less pronounced.

In terms of 'Vintage Aesthetics' the Nokton is superb. It is, as has been discussed many times, in essence a reworked 35mm v1 / v2 Sumillux and, at f1.4, shares many of the same optical aberrations which has endeared these old Summilux lenses to present-day snappers. Summilux to the left, Nokton on the right;

The 40mm f2.0 - whether Summicron or Rokkor made - will exhibit traits of the v2 / v3 35mm Summicron. The Nokton, similarly, renders in much the same fashion as the Summilux. It follows that all of these lenses could accurately be described as having 'Vintage Rendering'.

From my own experience with a 1974 v2 Summilux, an LLL '8 Element' (35mm v2 Summicron clone) and the Nokton I can say that from c. f2.8 down they all render in almost an identical fashion. It is highly unlikely(*) that anyone looking at photographic prints of images taken with these lenses in this aperture range could tell which snap was taken on which lens. All three lenses are very sharp when stopped-down; it is only when they are used at - or near - max. ap. that they show their 'vintage' character to the full. If this 'vintage' look is what is desired, then the way they render when used wide open should be a major determining factor.

If your Nokton has "stiff" focussing there is something wrong with your copy. These lenses are frequently noted for the smoothness of their focussing action.

The accuracy of the 40mm Summicron / Rokkor lenses has been raised in the forum a few times. From what I remember - and I might well be mistaken! - the issue is to do with the profile (i.e. slope) of the rangefinder-cam part of the mounting flange. These lenses were designed to be used with the Leica CL / Minolta CLE cameras of the 1970's. Being shorter than the M cameras the viewfinder and rangefinder windows are closer together than those of the M cameras which means that they have a correspondingly shorter rangefinder base. IIRC it is because of the different cam-shape which was neccessary for use with these shorter bodies that there may be issues but, again, how much of an issue this might be in actual use may depend on one's shooting preferences / typical subject-matter.

It might be worth doing a 'Forum Search' on this topic? Otherwise you might consider starting a new thread on the subject in the Leica M sub-forum as many forumites have these lenses and will be able to offer views based on experience gathered through actually using them.

Whether it might be worth a switch? Only you, I'm sorry happy to say, can be the judge. I'm fortunate enough to have lenses which cover all these bases but if I had to choose between the Nokton and a 40mm Summicron?.....I'd probably keep the Nokton. It has a really beautiful quality (IMO) when used wide-open - which the f2.0 lenses can't match - and is tack-sharp when stopped-down so the advantage of its rendering at f1.4 would most likely be the deciding factor for me.

Best of good fortune sorting out your own decision!

Philip.

* There are some circumstances where the optical aberrations of the Summilux might give the game away but that's another story for another time!...😸...

P.S. Do you like to use filters? If so be advised that the 40mm f2.0 lenses have an unusual thread pitch and filters / lenshoods are pretty much unique to these models. The UVa apart filters for use with the Summicron / Rokkor are scarcely to be found.

@pippy Thanks Philip. The diagrams helped a lot. I usually don't look into the diagrams and specs in this level of detail so it's quite refreshing to see the comparisons side-by-side.  Much appreciate your detailed explanation.

Yep, the 40mm f2 has a single rangefinder-cam vs the Leica duo. Supposedly that contributes to the slight variation in focus. Yes, I agree that 40mm f2 lens has quite a bit of short comings with the lens filter/hood, it's not the indented tab focus that I love (I will have to replace it) and I'll have to file the flange a bit to bring up the 35mm which I've already done so on my Nokton... etc etc. I had considered selling my M262 and summicron 35 to fund the Q3 43mm so I can get a "less maintenance" 40mm camera that has AF and MF experience. After reading your post, I may see if I can do some diagnostics on my Nokton 40mm. If indeed the stiffness is not what it is on mine, I may fix that instead. I've read some reviews that it does tent to be more stiff than the Leica 35mm if comparing the smoothness of the focus which is why I've let it slide over the years. That and I've been using 35mm for the past 9 years 95% of the time.