inconsistent focus depending on focus direction

[wizard]

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vor 2 Stunden schrieb hmzimelka:

As mentioned a few posts back. I'm fairly confident the camera is responsible for the largest error here, especially since I can see a lag in the rangefinder patch moving when I change focus direction from near to far.

Well, I believe what you see could be caused by the lens, not the camera. Let's assume, just for arguments sake, that your camera's rangefinder system has absolutely no lag or lash at all. And let's further assume the helicoid of your lens (or some other part of your lens'es focusing system) does have some 'play' or gear lash. Then, if you change the focusing direction, you will first go through that amount of play, and your camera's rangefinder system will initially not react at all, since no focusing movement is being transferred to the camera's rangefinder cam, resulting in the perceived lag in the rangefinder patch moving. As you continue the focusing movement (assuming no change in focusing direction occurs), the play or lash will be overcome, and you will see the rangefinder patch starting to move, as any further focusing movement will be transferred to the camera's rangefinder cam.

Based on the above thoughts, I am not at all sure that your M11 is responsible for what you see. 

Andy

[hmzimelka]

1 hour ago, wizard said:

Well, I believe what you see could be caused by the lens, not the camera. Let's assume, just for arguments sake, that your camera's rangefinder system has absolutely no lag or lash at all. And let's further assume the helicoid of your lens (or some other part of your lens'es focusing system) does have some 'play' or gear lash. Then, if you change the focusing direction, you will first go through that amount of play, and your camera's rangefinder system will initially not react at all, since no focusing movement is being transferred to the camera's rangefinder cam, resulting in the perceived lag in the rangefinder patch moving. As you continue the focusing movement (assuming no change in focusing direction occurs), the play or lash will be overcome, and you will see the rangefinder patch starting to move, as any further focusing movement will be transferred to the camera's rangefinder cam.

Based on the above thoughts, I am not at all sure that your M11 is responsible for what you see. 

Andy

I will be comparing it to another M11 or M10-R before sending it off, just to rule that out, but as mentioned the M11 and M3 show very different rangefinder patch behaviours. There is no detectable lag in the M3. Again, the system backlash of a lens is likely to exist but the degree to which it should cause an error should be within or very close to the DOF of the lens. I would be ok with that.

 

The error here is large. Testing this today again, at approximately 2 meters subject distance, the difference is around 3.5-4cm with the Summicron 50mm. The difference in focus with the Nokton 75mm is about 7.5-8cm. I mentioned that I think it's getting worse! ☹️

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First image focused from infinity. Focus is spot on where I want it, every time...

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Second image focused from close focus. Strong back focus at the same spot every time...

Edited September 26, 2022 by hmzimelka

[lct]

Can happen when there is some play in the helicoids of the lens. I would redo the test with an EVF, if you can find one, before returning the camera. 

[hmzimelka]

9 minutes ago, lct said:

Can happen when there is some play in the helicoids of the lens. I would redo the test with an EVF, if you can find one, before returning the camera. 

What test would you have me do? I can do it with the LCD on the M11 too. The problem is visible in every lens that I have, and its getting worse. How would all my lenses suddenly develop this problem. The Summicron 50mm is displaying the issue that I would have picked up when I bought it and did the initial testing. 

 

[wizard]

vor 30 Minuten schrieb hmzimelka:

I mentioned that I think it's getting worse!

Just another thought. Any play in the lens helicoids may be temperature dependent, not only due to thermal expansion, but also due to the fact that 'stiffer' grease will cover any play better than more liquid grease. As grease gets more liquid with increasing temperatures, there may be more play when a given lens is subjected to hot temperatures.

Try to cool down your lens somewhat and then redo your test. If the result improves, we may be on the right track. That said, I have used most of my lenses under varying temperature conditions (from -20 degrees C to about +40 degrees C), and have never noticed anything similar to what you have observed.

[hmzimelka]

2 minutes ago, wizard said:

Just another thought. Any play in the lens helicoids may be temperature dependent, not only due to thermal expansion, but also due to the fact that 'stiffer' grease will cover any play better than more liquid grease. As grease gets more liquid with increasing temperatures, there may be more play when a given lens is subjected to hot temperatures.

Try to cool down your lens somewhat and then redo your test. If the result improves, we may be on the right track. That said, I have used most of my lenses under varying temperature conditions (from -20 degrees C to about +40 degrees C), and have never noticed anything similar to what you have observed.

I have replace the grease in the 75mm lens with stiff grease and with light grease. Makes no difference. The issue is visible with every lens I have. Not just the Nokton 75mm. The Nokton with its fast aperture just makes the error very noticeable especially with its high performance wide open

[hmzimelka]

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21 minutes ago, lct said:

Can happen when there is some play in the helicoids of the lens. I would redo the test with an EVF, if you can find one, before returning the camera. 

I have mentioned that an image taken with focusing the lens from infinity to a specific mark on the lens barrel, and then to the same mark from the close focus point, shows a difference in focus, but it is so very very small that it doesn't bother me. This would be the error caused by the helicoid in the lens.

 

Edited September 26, 2022 by hmzimelka

[wizard]

vor 2 Minuten schrieb hmzimelka:

I have replace the grease in the 75mm lens with stiff grease and with light grease.

How did you do that? It requires to take the lens helicoid apart to remove and replace the grease, doesn't it? And to then correctly readjust the lens.

[hmzimelka]

3 minutes ago, wizard said:

How did you do that? It requires to take the lens helicoid apart to remove and replace the grease, doesn't it? And to then correctly readjust the lens.

Exactly. Not a difficult lens to take apart. Not difficult lens to assemble. There is nothing to adjust. If the one doesn't remove any shims, then the lens comes together as before.

I have a few years of experience taking manual focus lenses apart, and the only catch is to make sure where the helicoid threads exit each other and make sure these come together at the same place. This I do with tape or stickers and a sharpie marker to mark the exact point. 

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Edited September 26, 2022 by hmzimelka

[lct]

37 minutes ago, hmzimelka said:

What test would you have me do? I can do it with the LCD on the M11 too

Not sure it would be as accurate but you could try this indeed. Just put the camera on a tripod, aim at your target at the centre of the frame, focus with focus magnification from infinity to your target to begin with. When the target is sharp on the LCD, note the focus point on the focus scale of the lens. Then redo the same from the minimum focus distance. Note again the focus point and compare with the previous point. If there is a discrepancy between the two points, as i suspect it, you know that your culprit, or one of your culprits, is the lens. Next step could be to find a lens with zero discrepancy if any. 

[hmzimelka]

3 minutes ago, lct said:

Not sure it would be as accurate but you could try this indeed. Just put the camera on a tripod, aim at your target at the centre of the frame, focus with focus magnification from infinity to your target to begin with. When the target is sharp on the LCD, note the focus point on the focus scale of the lens. Then redo the same from the minimum focus distance. Note again the focus point and compare with the previous point. If there is a discrepancy between the two points, as i suspect it, you know that your culprit, or one of your culprits, is the lens. Next step could be to find a lens with zero discrepancy if any. 

I have already done this test. The focus position on the lens focus scale is identical to the point of me being not able to discern any difference.

The only lens I have that has this a little bit is the Hektor 13.5cm. But its not much at all. Certainly not enough to ruin an image.

The test that is easier to measure is pick a focus ring position that is easy to identify exactly repeatedly, and then take an image when the lens reaches this spot from both focus directions. The differences are then visible in the resulting images taken, which can be magnified in a photo editor. With the Nokton the difference is very very small, and with the Hektor its larger but still not enough to cause a problem

Edited September 26, 2022 by hmzimelka

[lct]

1 minute ago, hmzimelka said:

I have already done this test. The focus position on the lens focus scale is identical to the point of me being not able to discern any difference. [...]

 

I thought you did this test with the rangefinder. If you did it with the LCD, the rangefinder needs probably some calibration.

[hmzimelka]

9 minutes ago, lct said:

I thought you did this test with the rangefinder. If you did it with the LCD, the rangefinder needs probably some calibration.

I did three different tests...

By rangefinder calibration do you mean my rangefinder is responsible for the issue and needs servicing? 

[lct]

Just now, hmzimelka said:

By rangefinder calibration do you mean my rangefinder is responsible for the issue and needs servicing? 

I've been using those RF beasts for 30+ years so i would say yes indeed but i'm no techie so you may wish to ask other colleagues here for confirmation. To convince Leica, if needed, i would redo the test with a Leica lens preferably.

[Jeff S]

Why not just focus your lenses from infinity and carry on?

Jeff

[hmzimelka]

23 minutes ago, lct said:

I've been using those RF beasts for 30+ years so i would say yes indeed but i'm no techie so you may wish to ask other colleagues here for confirmation. To convince Leica, if needed, i would redo the test with a Leica lens preferably.

Yeah, sorry, with my reply I actually meant to differentiate that the rangefinder needs servicing versus calibration which feels like a more simple term/task... like the calibration a user could do at home with an Allen key. Anyways. I will be sending the DNG files to Leica, also those taken with the Summicron 50mm and my Tele-Elmarit 90mm once I get it back.

21 minutes ago, Jeff S said:

Why not just focus your lenses from infinity and carry on?

Jeff

If this is a serious question, then I'm not sure how to reply to this... If it would be acceptable for you to have to get by like this with a new (8 month old) very expensive Leica camera then thats fine. I certainly can't and I'm sure a lot of other would too. I will have to use it like this until I get an opportunity to send it in to Leica, but its certainly not acceptable from the product nor the brand. 

I would very much like to be in a financial position where money is no object, simply buy a new camera and send in the old one and not sweat the "small stuff"  but lets get back to the real world, at least for me 😂

Edited September 26, 2022 by hmzimelka

[Jeff S]

36 minutes ago, hmzimelka said:

Yeah, sorry, with my reply I actually meant to differentiate that the rangefinder needs servicing versus calibration which feels like a more simple term/task... like the calibration a user could do at home with an Allen key. Anyways. I will be sending the DNG files to Leica, also those taken with the Summicron 50mm and my Tele-Elmarit 90mm once I get it back.

If this is a serious question, then I'm not sure how to reply to this... If it would be acceptable for you to have to get by like this with a new (8 month old) very expensive Leica camera then thats fine. I certainly can't and I'm sure a lot of other would too. I will have to use it like this until I get an opportunity to send it in to Leica, but its certainly not acceptable from the product nor the brand. 

I would very much like to be in a financial position where money is no object, simply buy a new camera and send in the old one and not sweat the "small stuff"  but lets get back to the real world, at least for me 😂

Post #2.

And if it is an RF calibration issue, this has been a known issue with expensive M cameras for decades. It’s not for everyone.

Jeff

Edited September 26, 2022 by Jeff S

[Photoworks]

3 hours ago, hmzimelka said:

Yeah, sorry, with my reply I actually meant to differentiate that the rangefinder needs servicing versus calibration which feels like a more simple term/task... like the calibration a user could do at home with an Allen key. Anyways. I will be sending the DNG files to Leica, also those taken with the Summicron 50mm and my Tele-Elmarit 90mm once I get it back.

If this is a serious question, then I'm not sure how to reply to this... If it would be acceptable for you to have to get by like this with a new (8 month old) very expensive Leica camera then thats fine. I certainly can't and I'm sure a lot of other would too. I will have to use it like this until I get an opportunity to send it in to Leica, but its certainly not acceptable from the product nor the brand. 

I would very much like to be in a financial position where money is no object, simply buy a new camera and send in the old one and not sweat the "small stuff"  but lets get back to the real world, at least for me 😂

Sure sounds like your camera need a run to the shop. some calibration need to happen.

I have tested the same way my M 11 with a 90 summarit, 50 Noctilux, and 50 summilux, I suppose wide angles don't need this.

Well my results are the same each time focusing back and forward .

 

[ravinj]

5 hours ago, hmzimelka said:

I did three different tests...

By rangefinder calibration do you mean my rangefinder is responsible for the issue and needs servicing? 

You should send it to Leica. The way you are describing seems to be an issue with the M11. Don't accept the myth that "this is a known issue with rangefinders". My M11 was perfect with my usual lenses that I use for testing: Zeiss Distagon ZM 35 F1.4, FLE 35, VM 50 APO and Summilux 28. Wide open results were same using rangefinder focusing and magnified LV. 

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[FlashGordonPhotography]

11 hours ago, hmzimelka said:

Yes, this gear lash is somewhat easily tested when focusing the lens from infinity to a specific mark/position on the lens barrel and then comparing that image to one where the focus was achieved from the other direction. For the Nokton 75mm there is a difference but its very very little, far too little to bother me. With the Summicron 50mm its really not applicable. With the Hektor 13.5cm, there is a little too, but its too small to bother me.

Focusing the M3 with the Nokton 75mm f/1.4 from both directions results in a focus position on the lens barrel that is pretty much always the same no matter the direction. On my M11, the difference in focus ring position is quite large. Almost as wide as one of the DOF scale lines at a distance between 3-5 meter focus distance. 

The issue seems to be getting worse on the M11. As mentioned a few posts back. I'm fairly confident the camera is responsible for the largest error here, especially since I can see a lag in the rangefinder patch moving when I change focus direction from near to far. When I turn the lens the rangefinder patch moves with a slight delay. No lag the other way around when moving focus from far to near. 

Not on my M11. The 135 is the only lens I have that I even think about. Might be something in the RF mechanism.

Gordon