can a lens focus shift happen only on a particular camera?

[Rollei35]

Advertisement (gone after registration)

I recently acquired a lens which demonstrates some obvious focus shift at f/4 and f/5.6 at around 6-7 feet distance. It's about 1/3 feet back focusing at those apertures and distance.

However this focus shift only occurs on my M10-R, I cannot observe this behaviour when putting this lens on my M11.

I thought it's M10-R rangefinder issue, but all my other Leica lenses are fine with M10-R.

So basically, the focus shift only happens with this lens at f/4 and f/5.6 at distance around 6 feet on M10-R. It's this combination and this combination only exhibiting the problem.

Is it even possible?

[Al Brown]

Wetzlar Gods work in mysterious ways...

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[jaapv]

Yes that can happen. If the adjustment of the lens and camera happen to be adjusted in the right spot in the tolerance span the focus shift can be minimized. It sounds like your whole system needs to be calibrated. Your preferred Leica repair service should be able to do so within a reasonable time span and for an acceptable price. 

[lct]

2 hours ago, Rollei35 said:

I recently acquired a lens which demonstrates some obvious focus shift at f/4 and f/5.6 at around 6-7 feet distance. It's about 1/3 feet back focusing at those apertures and distance.

However this focus shift only occurs on my M10-R, I cannot observe this behaviour when putting this lens on my M11.

I thought it's M10-R rangefinder issue, but all my other Leica lenses are fine with M10-R.

So basically, the focus shift only happens with this lens at f/4 and f/5.6 at distance around 6 feet on M10-R. It's this combination and this combination only exhibiting the problem.

Is it even possible?

It is possible, dare i say, because it happens. Don't ask me why though. In my example, one of my favourite 50mm lenses is the Sonnar 50/1.5. It is a lens well known for its focus shift, that it does on all my RF cameras except the M11 where it is almost insignificant. I have no idea why but the Sonnar has now become my favorite fast 50 for people and portrait instead of the Summilux 50/1.4 v3.

[TomB_tx]

10 hours ago, lct said:

It is possible, dare i say, because it happens. Don't ask me why though. In my example, one of my favourite 50mm lenses is the Sonnar 50/1.5. It is a lens well known for its focus shift, that it does on all my RF cameras except the M11 where it is almost insignificant. I have no idea why but the Sonnar has now become my favorite fast 50 for people and portrait instead of the Summilux 50/1.4 v3.

I recently got an Amedeo adapter to fit my Contax Zeiss lenses on Leica M - and was indeed surprised at the images from a 1950s Sonnar 1.5 (as well as Sonnar 2.0 and Tessar 3.5). I haven't used them enough to quantify focus shift on my M10, but I suspect the 2.0 would not be an issue. (The rotation direction for controls is backwards however. Hope I don't like the images enough to make me buy the ZM version...)

[algrove]

Some say the worst focus calibration issues exist with the beautiful M 75/1.4. It is also said that it one of the few Leica lenses that can go out of calibration on its own.

[lct]

Advertisement (gone after registration)

1 hour ago, algrove said:

Some say the worst focus calibration issues exist with the beautiful M 75/1.4. It is also said that it one of the few Leica lenses that can go out of calibration on its own.

Curiously enough i never got the least issue with my Summilux 75/1.4. I got it second hand from a dealer who had it calibrated, which could explain that. No issue either with my Summicron 90/2 apo. I must be lucky i guess. I will probably never know as those are lenses i use preferably with EVF now.

[hjddd]

On 2024/3/10 at AM9点54分, lct said:

我敢说，这是可能的，因为它确实发生了。不过别问我为什么。在我的示例中，我最喜欢的 50mm 镜头之一是 Sonnar 50/1.5。这是一款以其焦点偏移而闻名的镜头，在我所有的 RF 相机上都有这种功能，除了 M11 之外，它几乎微不足道。我不知道为什么，但 Sonnar 现在已经成为我最喜欢的用于人物和肖像的 fast 50，而不是 Summilux 50/1.4 v3。

you may also try the ALPA 50 1.8 MACRO Switar ， is also magnificent ， after I compare it with E43， nokton 50 1.5 ltm and angenieux s1. 

[pgk]

On 3/9/2024 at 11:15 PM, Rollei35 said:

I recently acquired a lens which demonstrates some obvious focus shift at f/4 and f/5.6 at around 6-7 feet distance. It's about 1/3 feet back focusing at those apertures and distance.

However this focus shift only occurs on my M10-R, I cannot observe this behaviour when putting this lens on my M11.

It might be the camera which has a rangefinder roller which sticks for some reason with this particular lens. Difficult to check on a digital camera (you would have been able to set the shutter on a film camera to B, and then check through the back. Do other lenses work correctly with both cameras? 1/3 feet (~10cm) is a lot!

If you have no other problems with either camera or other lenses then I'd suggest carefully comparing this lens at the back with others as you change aperture, which may cause the whole internal lens barrel to move, just in case there is a discrepancy where the ramp engages with the roller and this is exacerbated by setting those apertures, when on the M10-R. It is possible that, as jaapv, says, the tolerances could be to blame and it is possible that something needs to be adjusted.

[Rollei35]

2 hours ago, pgk said:

It might be the camera which has a rangefinder roller which sticks for some reason with this particular lens. Difficult to check on a digital camera (you would have been able to set the shutter on a film camera to B, and then check through the back. Do other lenses work correctly with both cameras? 1/3 feet (~10cm) is a lot!

If you have no other problems with either camera or other lenses then I'd suggest carefully comparing this lens at the back with others as you change aperture, which may cause the whole internal lens barrel to move, just in case there is a discrepancy where the ramp engages with the roller and this is exacerbated by setting those apertures, when on the M10-R. It is possible that, as jaapv, says, the tolerances could be to blame and it is possible that something needs to be adjusted.

I just found out that this mis-focus behaviour on m10-r actually happens to some of my other lenses, but what puzzles me is it does not always happen.

All my lenses focus perfectly on M11 though.

With same lens, if I unmount and mount it to the m10-r couple of times, it will focus well.

I think you are right, it seems that the roller doesn't engage properly every time mounting the lens. Taking the lens off and re-mounting it fixed the problems most of the time, but again not always.

[TomB_tx]

I have occasionally seen where removing and replacing a lens cured a slight mis-focus issue. I recall once being advised to set lenses to closest focus distance before mounting, as this minimized interaction with the body focus follower until the lens was well centered in the mount. I haven't made that my standard practice - what about lenses with infinity focus lock?

[Rollei35]

30 minutes ago, TomB_tx said:

I have occasionally seen where removing and replacing a lens cured a slight mis-focus issue. I recall once being advised to set lenses to closest focus distance before mounting, as this minimized interaction with the body focus follower until the lens was well centered in the mount. I haven't made that my standard practice - what about lenses with infinity focus lock?

I just tried this "mounting-with-infinity-or-minimum-focus" ritual. It doesn't help.

I mounted/unmounted a Noctilux f/1.2 couple of times to it, it's still slightly forward focusing at f/2, I think about couple of centimetres.

While I tried APO-50 Summicron to the same camera, it's right on focus. Super sharp at f/2.

I know Noctilux and APO are two different beasts. But I can pretty much tell what off focus is at f/2.

I gave up, I just leave APO to the m10-r, and let Noctilux sit on m11.

[mokona]

I had something similar with a 50mm lux Asph that was spot on with a M240-P but totally off with a newly acquired M246. I suspected the M246 and sent it for calibration and when it came back, I still had the same issue.

I brought it to a Leica store with the 2 bodies and they were puzzled as well. In the end the lens was sent to Wetzlar and it came back fixed.

(then I sold it coz I got a sonnar zm haha)

[Rollei35]

3 hours ago, mokona said:

I had something similar with a 50mm lux Asph that was spot on with a M240-P but totally off with a newly acquired M246. I suspected the M246 and sent it for calibration and when it came back, I still had the same issue.

I brought it to a Leica store with the 2 bodies and they were puzzled as well. In the end the lens was sent to Wetzlar and it came back fixed.

(then I sold it coz I got a sonnar zm haha)

I am really curious why though.

My scenario is that I have M cameras 1 and 2, and M lenses A, B, C, D.

There could be 8 combinations: 1A, 1B, 1C, 1D and 2A, 2B, 2C 2D.

This kind of off-focus phenomena only exhibit on the combination 1A and 1B with apertures f2.8 to f4, nothing else.

Could it be lenses A and B problem, or body 1 problem?

I am very puzzled. It just doesn't make sense.