Noctilux myths

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TJV

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Hello all,
still waiting on my Noctilux and have been reading some people complaining (on stupid digi pixel obsessed forums) about back focus issues. Have any of you film and Nocti users out there incountered this focus shift issue in real world practice?
What other pros/cons of this lens are there? I'm not talking about it's fingerprint here, purely how it behaves / handles in real world use.
Cheers,
Tim
 
I use mine a lot. Landscapes, night, low light. Never had a single problem, never had the focus shift issue.
I thought long and large about it and I think it's just a miscalibration issue: Glass Versus barrel movement. That's all. Theoretically, the problem should be physical and not optical. Otherwise what would explain that SLRs don't have that problem?

Here's a critical shot:
Web-Paris2007-6.jpg
 
Focus shift is a known issue in optics, it exists, and is well documented. However, while some people find it makes a lens unusable, others never encounter it as a practical problem. E.g. I *know* that Sonnar designs have very substantial focus shift, but it is yet to ruin me any photo.
 
No myth

No myth

The back focus of the Noctilux is buffered by the thickness of the film emulsion, which is why it poses a more significant problem on the M8 than other M cameras.

My E58 Nocti gets absolutely thrashed and as far as I can tell its only real weaknesses are that it is too big and heavy and only focuses to 1m. For some critical applications wide open, the contrast under 1.5-2m can be low, but there are ways around it.

The only real 'myth' I hear persistently about the Nocti is that it doesn't work as well stopped down.
 

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Freakscene said:
The back focus of the Noctilux is buffered by the thickness of the film emulsion, which is why it poses a more significant problem on the M8 than other M cameras.
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Click to expand...


would you have 'front' focus then? because the buttons are more in focus than the face?
 
Mine (E60) works fine on film or M8. The 75 /1.4 had to go in for adjustment due to severe back focus with film and M8. It's hard to predict so it's a matter of try and and see. With the M8 you can immediately know if their is focus issues - as long as you are doing your part to focus accurately. Which with a 1.0 lens is tricky. I'd suggest a tripod to be sure it's the lens and not you swaying and losing focus.
Steve
PS: And it is superbly sharp when stopped down!
 
Most SLRs are focused with the lens wide open and then the lens automatically stops down for imaging as the mirror goes up. Unless the focus was checked stopped down, any shift caused by stopping down would not be seen in the viewfinder.
 
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The focus is calibrated to work at 1.0. By 2.8 and more so at 5.6 there is a definate shift and it hurts the the resolution.

All fast lenses shift unless there is some mechanical compensation built in.

I have a Gunter Osterlow with a chart comparing the 50 1.4, 50 2.0 and 50 1.0. He even tells how much compensation to add to the focus manually to bring the resolution up at small stops.
 
Spherical and chromatic abberation do not change focus, they change spot size. Or in other words, they reduce resolving power. If spherical abberation (SA) is bad wide open, shifting the image plane does not make it better. The focus of a lens should be at the image plane regardless of SA and stopping down does not change that plane.

If your fast lens is not focusing properly wide open, the rangefinder or lens coupling needs to be adjusted. You can say "focus shift" is a myth.
 
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It's good to hear that ALL of you are happy with your fast Nocti and 75 lux (after adjustments.) All the hype over at the Leica forum got me thinking about it. Hype will do that, especailly after waiting patiently for over nine months for a once in a lifetime lens that you've pre-paid for!

I think I'm in the same camp as you, NB23. I would like to use the Nocti as almost an everyday lens. The size is fine for me and I mean what's the point in spending money on something like a Nocti if it's going to be used only once in a while as a one trick pony? Keep a good medium speed film in one camera with the lens mounted and I've got a versitle "go anywhere" kit, all be it a little bit slower to focus than a 50 'cron. My point is, if the focus shifting is a cause of concern mainly with digi (and even that seems debateable,) then I have noting to worry about.

My one question now though... Why is CA a bigger issue with digi? I know that the sensor is flatter than a films surface, but how could that emphasize what appears to be focus issues? I mean, in an ideal world film should be kept perfectly flat too. It wouldn't make sense to optimise a lens for something thats not consistantly flat. Do you know what I mean? Someone said something about the thickness of the film. How would that work? Isn't it only the light exposed surface that matters? Or are you meaning that each film is slightly different in thickness so the designers just adjust the lens to an ideal specification? The other think I was thinking about is perhpas it could be emphasized by the thin filters / glass that's placed over the top of digi sensors? Some kind of refraction problem?

I just don't see why CA and it's associated issues are more of a problem with digi...
 
TJV said:
My one question now though... Why is CA a bigger issue with digi? I know that the sensor is flatter than a films surface, but how could that emphasize what appears to be focus issues? I mean, in an ideal world film should be kept perfectly flat too. It wouldn't make sense to optimise a lens for something thats not consistantly flat. Do you know what I mean? Someone said something about the thickness of the film. How would that work? Isn't it only the light exposed surface that matters? Or are you meaning that each film is slightly different in thickness so the designers just adjust the lens to an ideal specification? The other think I was thinking about is perhpas it could be emphasized by the thin filters / glass that's placed over the top of digi sensors? Some kind of refraction problem?

I just don't see why CA and it's associated issues are more of a problem with digi...
Click to expand...

Why do you think CA is a bigger digital issue? Could this be because people are finally enlarging their images in photoshop and peeping at pixels?

The film plane is at the gate and so the thickness of the film is not an issue unless the pressure plate is hindered from keeping the film against the gate. The film does not have to absolutelt flat, just within the depth of focus tolerance. Flatter sensor planes are not a problem.

You are right that the glass over the sensor can be a problem, not so much with refraction, but tranmittance that it sends the image plane further back, but the designers should know this and place the sensor plane in the appropriate position.
 
I think there are three reasons:

- film vs. sensor flatness: film will bend inwards the film gate slightly. Which might cause a film-adjusted lens with very shallow DOF to back-focus on a digital camera, I guess. Obviously more in the center of FOV.

- it is much, much easier with a digital camera to test a lens. And, the Noctilux has become much more popular with the M8. I think some of the issues discovered today with the M8 existed in the past but remained undiscovered.

- with the crop factor, the DOF decreases. That is, you are effectively dealing with 65/f1.0 and 100/f1.4 lenses on the M8 when considering Noctilux and 75 Summilux. Harder to focus on M8. I would guess that many Nocti and 75 Summilux film users used .85 or .91 viewfinders, before the M8 hit the market.

I don't think film thickness is important.

Best,

Roland.
 
Finder said:
Why do you think CA is a bigger digital issue? Could this be because people are finally enlarging their images in photoshop and peeping at pixels?

The film plane is at the gate and so the thickness of the film is not an issue unless the pressure plate is hindered from keeping the film against the gate. The film does not have to absolutelt flat, just within the depth of focus tolerance. Flatter sensor planes are not a problem.

You are right that the glass over the sensor can be a problem, not so much with refraction, but tranmittance that it sends the image plane further back, but the designers should know this and place the sensor plane in the appropriate position.
Click to expand...

Well, it could just be pixel peeping. I'm just wondering why it's suddenly become an issue and is unacceptable to one group but perfectly ok with another. Maybe it's also an issue because the M8 is not full frame so the enlargements are of greater magnification? The 1.33x crop factor playing it's part to emphasize any intollerances combined with pixel madness?
 
Finder said:
f your fast lens is not focusing properly wide open, the rangefinder or lens coupling needs to be adjusted. You can say "focus shift" is a myth.
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You can say that and you will be wrong 🙂 SA has more than one consequence.

Due to spherical surface of the lens, the point of best focus is different with full opening and with peripherial areas closed out. Check out e.g. this article.
 
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varjag said:
You can say that and you will be wrong 🙂 SA has more than one consequence.

Due to spherical surface of the lens, the point of best focus is different with full opening and with peripherial areas closed out. Check out e.g. this article.
Click to expand...

Perhaps you can tell me the connection between HTTP and SA? Are you sure you have the right link?
 
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