Caliber 75mm Noctilux

[dubrow77]

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Hello Forum,

What’s the best practice to test if a 75mm Noctilux is properly calibered? I used a M10M and also have an EVF. (I wear glasses. So I don’t want my old eyes to affect the results ☺️)
 

thanks,

benjamin

[lexffm]

Hello dubrow77,

I can first recommend that you take off your glasses and buy a suitable compensation lens for the manual viewfinder. You have to test it, it's best to try it out in the Leica store, similar to the optician. Remember that all M's have -0.5 diopters.

Now the question is, what exactly are you worried about, that an image is not sharp in the place you expected it to be?

If you look at the attached depth of field table, you will see that the question is whether it is incorrectly calibrated or is the way it is due to the desired shallow depth of field at full aperture and short distance.

In any case, use the focusing aid, preferably manually and on the thumbwheel.

If necessary, you can also set a few images with Exif information as a description.

BR, Alex

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Here's another example of what I mean. The eye on the left is quite sharp, including the eyelid, but the eye and the eyelid are not. The distance was about 3-3.5 m and the aperture was between 1.25 and 1.4 (if I remember), so not even fully open. I thought I was standing at exactly a 90 degree angle, but unfortunately that wasn't the case.

Edited November 12, 2024 by lexffm

[SiggiGun]

The lens is not “calibrated”, but in the given case, the camera is adapted to the lens. If this is necessary, you should make sure that the camera is set to the lens that is used most often. The 75Lux is a non FLE, i.e. there is “focus shift” both at open aperture and at close range. This is due to the design. If such a lens is used as described, this is best done with an EVF or in LV mode. 

[250swb]

21 minutes ago, SiggiGun said:

The lens is not “calibrated”, but in the given case, the camera is adapted to the lens. If this is necessary, you should make sure that the camera is set to the lens that is used most often. The 75Lux is a non FLE, i.e. there is “focus shift” both at open aperture and at close range. This is due to the design. If such a lens is used as described, this is best done with an EVF or in LV mode. 

That is not how Leica 'calibrate' things. Both the body and lens are set to their own tolerances which means they can work together, or the body with other lenses or the lens with other bodies. It is an amateur practice to make the body adapt to one lens and make it useless with other lenses.

But the OP's lens may not need calibrating, so with an EVF or the LCD focus on a wall and see if what is in focus corresponds with focusing using the optical viewfinder. Keep in mind the test should be done with the lens wide open or there will be some leeway due to DOF.

[SiggiGun]

vor 6 Minuten schrieb 250swb:

That is not how Leica 'calibrate' things. Both the body and lens are set to their own tolerances which means they can work together, or the body with other lenses or the lens with other bodies. It is an amateur practice to make the body adapt to one lens and make it useless with other lenses.

But the OP's lens may not need calibrating, so with an EVF or the LCD focus on a wall and see if what is in focus corresponds with focusing using the optical viewfinder. Keep in mind the test should be done with the lens wide open or there will be some leeway due to DOF.

I guess I wasn't clear. Of course, the camera has to be adapted to a lens, and not the other way around. This includes both the camera and the lens! What I wanted to say is that the calibration screw is on the camera and not on the lens. Ideally, of course, a good compromise should be found. 

[250swb]

1 hour ago, SiggiGun said:

I guess I wasn't clear. Of course, the camera has to be adapted to a lens, and not the other way around. This includes both the camera and the lens! What I wanted to say is that the calibration screw is on the camera and not on the lens. Ideally, of course, a good compromise should be found. 

No, the camera should never be calibrated to the lens and the lens should never be calibrated to the camera. They should both be calibrated to their own tolerances set down in the manufacturing or service specifications. 

[evikne]

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I would buy one of these. The large grid pattern is easy to focus on with the rangefinder. I use mine to check the calibration when I've got a new lens, or got a lens back from service.

https://www.datacolor.com/spyder/products/spyder-lenscal/

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[3D-Kraft.com]

vor 8 Stunden schrieb SiggiGun:

The lens is not “calibrated”, but in the given case, the camera is adapted to the lens. If this is necessary, you should make sure that the camera is set to the lens that is used most often. The 75Lux is a non FLE, i.e. there is “focus shift” both at open aperture and at close range. This is due to the design. If such a lens is used as described, this is best done with an EVF or in LV mode. 

Seems like you are talking about the 75mm Summilux. The TO is talking about the 75mm Noctilux, which is a FLE design and better focus precision accross the typical distances range.

@dubrow77 Look for someone with good eyesight and let him/her focus the rangefinder to a target that contains contrasty vertikal lines. Now, compare it with the live view magnification in the EVF.

Edited November 12, 2024 by 3D-Kraft.com

[SiggiGun]

vor einer Stunde schrieb 3D-Kraft.com:

Seems like you are talking about the 75mm Summilux. The TO is talking about the 75mm Noctilux, which is a FLE design and better focus precision accross the typical distances range.

@dubrow77 Look for someone with good eyesight and let him/her focus the rangefinder to a target that contains contrasty vertikal lines. Now, compare it with the live view magnification in the EVF.

You’re right. I apologize for this

[dubrow77]

Thanks to all of you for you insights 

 @3D-Kraft.com 75mm Noctilux. 

I will use the EVF for testing and focusing using @evikne's data color tool.

Is there a best practice on how to proceed? ex: Lens fully open and taking shot at different distances, repeat by closing the aperture to the next stop. For each picture, focus using the EVF, and verify that the range finder is aligned to the same focus point? 

Thanks,

 

Benjamin  

[evikne]

32 minutes ago, dubrow77 said:

Thanks to all of you for you insights 

 @3D-Kraft.com 75mm Noctilux. 

I will use the EVF for testing and focusing using @evikne's data color tool.

Is there a best practice on how to proceed? ex: Lens fully open and taking shot at different distances, repeat by closing the aperture to the next stop. For each picture, focus using the EVF, and verify that the range finder is aligned to the same focus point? 

Thanks,

 

Benjamin  

Feel free to do it as you say. Many people seem to prefer to focus with an EVF and compare with the rangefinder immediately. Personally, I prefer to focus with the rangefinder and take pictures. Then I can study the images on the computer afterwards.

To detect focus shift, put the camera on a tripod. Focus at full aperture and take a picture, stop down one stop and take another picture, and so on. Then you will see if the focus changes from image to image.

Here's a test I did a while ago that revealed focus shift on another lens:

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Edited November 12, 2024 by evikne

[dubrow77]

Thanks @evikne. This is helpful. Then do you repeat the test at different distances too? 

[evikne]

9 minutes ago, dubrow77 said:

Thanks @evikne. This is helpful. Then do you repeat the test at different distances too? 

Different distances can be useful for checking calibration, but perhaps less important for focus shift.

[Jean-Michel]

9 hours ago, evikne said:

I would buy one of these. The large grid pattern is easy to focus on with the rangefinder. I use mine to check the calibration when I've got a new lens, or got a lens back from service.

https://www.datacolor.com/spyder/products/spyder-lenscal/

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Or you can make your own similar device by downloading and building the target. I made one some years ago and it worked well to micro-calibrate Canon 5d2 s and check M lenses. See: https://squit.co.uk/photo/focuschart.html

Edited November 12, 2024 by Jean-Michel
typo

[mdg1371]

One important note about the 75mm Noctilux— mine is calibrated accurately— however, in doing extensive testing I noticed that you can achieve critical focus, and then move the focus ring so slightly that the RF split image does not change in any perceptible way, and focus will be off. I was able to consistently repeat this on a tripod mounted set up. The movement of the ring is so minimal that it’s borderline unnoticeable, but it can easily happen just from the mass of the lens in hand. 

[3D-Kraft.com]

Yes, the 75mm Noctilux demonstrates the limit of the range finder concept.

[farnz]

On 11/14/2024 at 11:52 AM, mdg1371 said:

One important note about the 75mm Noctilux— mine is calibrated accurately— however, in doing extensive testing I noticed that you can achieve critical focus, and then move the focus ring so slightly that the RF split image does not change in any perceptible way, and focus will be off. I was able to consistently repeat this on a tripod mounted set up. The movement of the ring is so minimal that it’s borderline unnoticeable, but it can easily happen just from the mass of the lens in hand. 

This is the reason I gave up using my 75 Noctilux with my M10 (unexpected oof subjects) and now use it with my SL2-S where shooting TTL is more reliable and minor changes in focus can be caught with the magnifier.

Also I feel that (for me) the 75 Noctilux works better with the SL2-S and is a bit front-heavy with the M10.  The 75 Noctilux does produce gorgeous pictures though.

Pete.

[dubrow77]

1 hour ago, farnz said:

This is the reason I gave up using my 75 Noctilux with my M10 (unexpected oof subjects) and now use it with my SL2-S where shooting TTL is more reliable and minor changes in focus can be caught with the magnifier.

Also I feel that (for me) the 75 Noctilux works better with the SL2-S and is a bit front-heavy with the M10.  The 75 Noctilux does produce gorgeous pictures though.

Pete.

I don't mind the balance of the M10M. Just need to carry my EVF around. And agree, the rendering is beautiful 

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