Infinity focusing on fast M lenses

[Elsu]

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I have been troubled by my 35cron ASPH and Monochrom.

I have discussed about the issue in another thread, but here is a related question I wonder about.

 

Even with very fast lenses, if you

- push the focus ring to the very end and focus at infinity

- the subject is very far away, eg 1 km

shouldn't the subject be at least reasonably focused and sharp, even though the aperture used is f2 or even f0.95, and it is the maximum aperture?

 

Attached is a comparison, 1:1 crop, left is f2 and right is f4.

Those structures are at least 1 km away.

Note that (mentioned in another thread) in close focusing tests I found this 35cron frontfocuses at least by 1.5cm.

 

I have tried to look for some answer around, reading about hyperfocal distance, infinity, and used some depth of field calculator.

From one calculator, with 35mm at f2 and subject distance 1km, DoP near limit should be 20m, far limit infinity, total infinite, hyperfocal distance 20.5m, circle of confusion 0.03mm.

 

I have yet to try to focus my N095 at infinity at f0.95.

But based on all the information I have read, I would think this 35cron of mine still has issue, and infinity should really be infinity, which does not need smaller aperture to pull out more focus/sharpness.

 

 

Or then can a mis-alignment with the rangefinder body affect the inifnity focusing and sharpness in this case?

Or can overexposure also affect the result anyhow?

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[JWW]

A while back, I had a 35 Summicron ASPH that was soft at infinity stop wide open. I sent it in to DAG and he adjusted it perfectly.

 

I would suggest that you send it in to Leica, DAG, or other specialist and get the lens adjusted correctly.

[Jerren]

Perhaps Andy's explanation from this thread applies here?

 

Bill, your explanation is correct for SLR lenses (even some Leica R lenses) that allow to focus past infinity, but cannot be true for any rangefinder coupled lens. With an SLR, you are able to actually see when the image is in focus, no matter whether that requires to turn the lens beyond the infinity position or not, but not so with a rangefinder camera. Therefore, every rangefinder lens MUST be adjusted to give true infinity at the indicated infinity position of the lens. Whether the rangefinder image also coincides is again another matter. In other words, the lens may be optically correctly adjusted for infinity, but the rangefinder image may be off, because the rangefinder cam of the lens is maladjusted. Or the rangefinder images may coincide at the infinity position of the lens, but the image may still be out of focus, as the lens may optically be maladjusted.

 

Cheers,

 

Andy

[Elsu]

Thing is, as mentioned the other thread (linked in OP), I did send the lens back to Solms and it came back with a report saying the optics was adjusted on M8/M9 and image quality tested. The images attached here and in the other thread were all taken now after the lens has been to Solms, ie some issue is still not fixed. I did not send the Monochrom along, though.

 

Another thing, when I did the infinity focusing test, as the focusing ring was set at the infinity mark, the images overlapped just fine in the viewfinder.

 

If infini is infinity even at 0.95, then I suppose I need to send both the body and lens back to Solms for an adjustment.

But is the lens off or can the body also be off? They told me that lenses are adjusted and tested in factory against their reference cameras. So now the lens came back from the factory, it should be up to the "standard", right? And does that mean my Monochrom is not up to the "standard"?

My N095 actually focuses fine with the Monochrom. So, would it be worth it to ask them to adjust my 35cron off the "standard" to fit my Monochrom?

[JWW]

Did you get a chance to try the 35 cron on another M9? If you can verify that the lens is off focus on other known good M9s, then I would tend to believe that the lens is still not adjusted correctly.

[algrove]

Elsu-I would not have it adjusted off spec, but instead just see if your camera(s) is off by sending it into Leica.

 

From my understanding if both are in spec then there should be an overlap. The specs should be wide enough to generally work even if one or both are to one side or the other of "center" spec.

 

I have had Leica suggest to send in a camera and specific lens to calibrate together, but then if I do this then there is a chance all my other lenses might be out of adjustment.

[Elsu]

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Was talking with my local Leica agent. They suspect the sensor could be just a tiny bit too close to the mount. I have no idea if that is possible. But anyways, both lenses and the body now are sent back to Solms. They said it take 2-3 weeks. Lets see about ti then.

[Elsu]

So finally I got the Monochrom and lenses back from Germany.

The focusing seems to work perfect with both lenses. Especially with the Summicron 35 slowed down, the images really showcase the superiority Monochrom possesses.

 

I did some testing shots. Left half shot at f2, right half at f5.6. Attached are comparisons from the same pair of images.

 

The first one shows an area from center to left.

I suppose the little blur on the white building comes from the fact that it is 1/3 of the center towards the image left edge. The center does not really show any difference between the apertures.

 

The second image shows the left edge (9 o'clock) of both shots.

I suppose even with such a superior lens, there can be such a difference on the edge between f2 and f5.6.

 

I certainly hope so, or else that would mean there is still something wrong with my lens shooting at f2 set at infinity.

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[250swb]

Any lens is going to be better at f/4 or f/5.6 than it is at f/2, so stop it down if you are doing landscape pictures.

 

Steve

[Orient XI]

One of the main problems with photographing distant subjects is the dirty, hazy, turbulent air between you and the subject. Twinkle, twinkle little star applies.

[Fgcm]

Elsu, most lenses (including Leica's) focus beyond infinite.

This is caused by tolerances.

 

Solution: do not send lenses to Leica. You do not need it.

 

Take some pictures to something not too far away.

One hundred meters (not more) is ok.

Braket focus stepping back just a little for each picture and check which is in perfect focus at maximum aperture.

 

Now you "know your lens" so you know that you can focus the true infinite just a little before the focus ring stops at the end of it's throw.

 

This is inexpensive.

 

You will be surprised seeing how the picture can be affected by a lens focused beyond infinite.

 

Know your stuff!

 

Franco

[skinnfell]

I cannot give you a proper diagnosis, but I can say that given the shutter speed shown (and assuming you didnt shoot it from a speeding car), the level of sharpness in your samples is unacceptable, at both apertures, particularly if we are talking about a center crop with standard lightroom sharpness applied.

[jankap]

I tend to agree with skinnfell.

Could you give us the crop factors of the images? And the overview picture itself too.

 

Could you try another camera (MM, M9 or M240)? From your dealer perhaps?

Jan

[Elsu]

@skinnfell

By "unacceptable", if you mean those 2 last images shot at f2 (left), that worries me a little bit. Note that the first of the last 2 images is a center crop.

 

@jan_kappetijn

The crop factor for both last 2 images is 1:1.

Here you can see the original image shot at f2. There is only the standard LR sharpening applied 25, 1.0, 25.

Have not tried on other bodies. I used to have a M9 and as far as I remember I never got better sharpness on M9 than this now. Of course, the fact that the current shots come out from MM probably makes a difference.

What got me started to "fix" this Summicron was when I saw the comparison test I did at a dealer, see the first image in this thread.

 

@fgcm

I have to say that this tolerance issue came as a big surprise. Apparently such an issue was not really an issue in the 15 years shooting film.

It is definitely crucial to "know your lens" or "know your equipment". What frustrates me in this case is I cannot tell what the proper/standard/factory performance (of this lens combined with this camera) should be. Without seeing or knowing that performance for real, it is hard to see how much compromise I am making or need to make, i.e. how much more hassle I would like/need to go through to tune this.

 

This headache is also partially caused by the general "Leica expectation". With my Olympus, Canon and Voigtlander bodies and lenses I hardly care about such issues. Apparently they do not bear such a "promise to deliver" as Leica does (or presumed to do so).

"Promise to deliver" if the photographer wants it to.

 

The thing before I sent the gear to Germany seemed to be even I wanted to, and tried different ways, I could not be sure I could get it to.

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