M8 + Nokton 50/1.5 focus

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Stephen G

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I have recently started using a Nokton 50/1.5 on my M8.

I feel I am seeing backfocus at close range. If I am focused near minimum range.. 0.9m to 1m, focus looks like its off by about 0.5 to 1 inch. Obviously wide open at minimum range is really pushing the rangefinder, calibration, and my eyes to the limit. However the focus is consistently back.

I had previously used a 35/1.4 Nokton and not seen issue, but the 50/1.5 is far more demanding on the RF and has far shallower DOF.

What are the most likely culprits, and how can I diagnose-
* Lens itself (Used Nokton 50/1.5)
* LTM-M adapter (Voigtlander Type I 50/75)
* Body itself (Used Leica M8)



Thanks
Steve
 
You're measuring from the sensor plane (rear of M8 body) right?

Try to see if you can go to a dealer and try a few other M-mount lens, or m-adapters.

I think it is more likely to be the lens than the body.
 
ampguy-
Haven't gotten out a ruler yet (I should set up a tripod and due so).

I mean that I focus on subject via the RF in-camera, and the resulting image very clearly shows focal point being 0.5 to 1 inch back from what I set.

It's especially clear in portraits when setting focus on eyeballs..
 
Ok

Ok

I still think it's more likely the lens than camera, but here's another thing to try -

Try up close, and stopping down to f2 and 2.8. If it's spot on there, you may not want to adjust it for 1.5 min distance, as you might be off when you stop down.

This is focus shift, and many Sonnar type lens have it.


Stephen G said:
ampguy-
Haven't gotten out a ruler yet (I should set up a tripod and due so).

I mean that I focus on subject via the RF in-camera, and the resulting image very clearly shows focal point being 0.5 to 1 inch back from what I set.

It's especially clear in portraits when setting focus on eyeballs..
Click to expand...
 
0.5 to 1 inch at close focus is within the tolerance of your entire system. Different LTM adapters, lack of tripod use, not focusing using the patch center, a very slightly misaligned camera, etc., can cause that small error. In practice it shouldn't matter, in other words, other things (like movement of your body or subject) will cause more error.

Focus shift should be no problem with the Nokton 50/1.5 ASPH.

Roland.
 
FWIW, I just read a Sean Reid review, he says that the Nokton 1.5 does not have focus shift, and I believe he uses M8 on his tests. The (CV) Asph lenses supposedly do not have focus shift on dRFs, but there is always the elusive "sample variation".
 
An unrelated question-
Does the forum software have a bug, or is JSU a really busy guy?

JSU
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I once purchased a used 50/1.5 Nokton and it most certainly had focus shift on my M8. Really bad focus shift. The seller took it back and reproduced my results on his M9. I wrote Stephen Gandy (not purchased from him) and he replied that it is very, very rare.

A flickr set demonstrating Nokton shift

What's funny is I never bought another one. Instead, I went a little crazy and went out of my way to then purchase a used 50mm Sonnar, which is what I wanted anyway, and is a lens that is an admitted and well-known "focus shifter". My copy is optimized for f/1.5 focus, so I'm happy with it.


(Well ... I was, until I accidentally slammed it into a piece of furniture, and apparently bent the internals all to hell so that the optical unit now rattles. It's at Zeiss awaiting repair. This is becoming one expensive used lens.)
 
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If you have these criteria, which not everyone will, you'll end up with only 1 option, the 50 lux V2:

1. Smaller than a Noctilux or Nokton 1.1
2. 1.4 or faster
3. No discernible focus shift between 1.4 and 4
4. No wacky distortion
5. No flare issues
6. No wacky bokeh
7. No decentering
8. very sharp, especially in the center
9. accurate color reproduction
10. good balance of contrast
11. solid build quality, no cheapo components
 
Stephen G,

It is a good reason to believe that both your M8 and your Nocton 1,5 is focusing OK. It is normal that a fast lens like the Nocton do front focus at close distance. When stopping down the DOF increases and the senter moves backwards. This is something all lenses do. It is only visible with the fastest lenses.

I had my M8 and Noctilux sent to Solms twice. For the same reason. It turned out that it had been OK from the start. All fast lenses do front focus a little - the faster/the more.

Which shows the disadvantage of these super fast lenses. Those dreaming of a 50 mm 1,0 Noctilux; be happy with just anything not so fast. I would argue that it is close to impossible to focus a Noctilux corrently at distances closer than 2 meters at wide open aperture. You need an eyesight of an eagle. Litterally.
 
It may be the Adapter.
I have had the same back focus issue. I switched adapters with one from my 28mm (focus was right on)and it focused correctly.
I resolved the problem by putting a very thin piece of tape between the adapter and lens. In this case, you are shimming the lens for back focus or thickening the adapter by just a bit to correct the problem.
Give it a try. Cost's nothing and may resolve the issue
 
lewis44- Adapter is something I considered. I will try swapping with the adapter on my 15/4.5 vc. On the other hand, this may be a good excuse to order a codeable VC type 2 adapter for the 50 and see if it works.

JSU- What I figured, just thought I'd have some fun.

Anyway, probably time for me to go find a meter stick as well.
 
Well it would appear to be the adapter.

Focus tested it with the adapter off my 15/4.5 and looked much better.

Now-
Notice how differently the lens mounts on camera between my two adapters. Looks like its overrotating into the bad adapter.

Filenames indicate which is which 🙂
 

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interesting

interesting

which adapter worked well, and which didn't?

Stephen G said:
Well it would appear to be the adapter.

Focus tested it with the adapter off my 15/4.5 and looked much better.

Now-
Notice how differently the lens mounts on camera between my two adapters. Looks like its overrotating into the bad adapter.

Filenames indicate which is which 🙂
Click to expand...
 
The bad adapter was a type-1 50/75 voigtlander adapter. It was old, used, came with the lens. Showed a bit of wear on the writing, maybe been mounted & dismounted often.

The good adapter was a type-2 28/90 voigtlander adapter, bought new about 2 months ago.
 
Thanks

Thanks

Good info. Ferider (Roland) also mentioned noticing the CV type 1 adapters are thinner than CV type 2 and Leica M to LTM adapters. I haven't noticed, and have all types, but mostly use them on wide lens like 15s, 21s, 28s.

Stephen G said:
The bad adapter was a type-1 50/75 voigtlander adapter. It was old, used, came with the lens. Showed a bit of wear on the writing, maybe been mounted & dismounted often.

The good adapter was a type-2 28/90 voigtlander adapter, bought new about 2 months ago.
Click to expand...
 
I'll join in the topic. Recently, I think my 50mm 1.5 is back focusing as well. When I try to focus on an object at infinity, I can't align the images even when I fully turn the barrel. It seems I need to turn a little more to align them. Therefore, if I have been turning the barrel more everytime when focusing at all distances, technically I'm focusing a little to the back?
 
Has anyone measured the Type 1 thickness vs the Type 2's?

Before they had 2 types, the CV adapters I had usually matched my Leica/Leitz adapters as far as focusing accuracy. I think I have 1 CV type 2 28/90 adapter, but it is on very wide lens like a 15 or 21 and works fine there.
 
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