rangefinder coupling accuracy and adjustment

[geotrupede]

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hi there.

I have noticed the some of my lenses (namely the leica ones) are very accurate with focusing and rangefinder on a M11. however some other lenses from third parties show a significant error in close focus. This is at full aperture, we are talking about f1- f1.4 for all experiments.

Now, as the leica lenses are correct with focus, the issue seems to be with the other lenses.

A calibration issue:  can it be fixed in some way, by rotating the profile of the focus within the lens? is this possible at all? is it a simple adjustment or requires a complete redo of the lens?

To note, all lenses are native m mount for leica cameras, digital, and are modern.

Also, this is not focus shift, the error is about 30 cm, quite large and happens at all the apertures with a shallow DOF.

As I seldom shoot wide open, I did not realise this issue until recently 😉

Any insight appreciated,

Thanks

G.

 

ps

My lens, which I love, and has this issue, is a MS apollon 36mm. a fantastic lens, I would love to fix the issue as I like the compactness and the images

 

 

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[spydrxx]

I have neither this lens nor an M11, but a lot of 3rd party lenses which I use on my LTM and M mount film bodies as well as on a Sony A7rii. Most have no issues with close focus accuracy. I suspect in your case the shape of the lense's rangefinder pusher may not perfectly match the shape of the camera body's rangefinder cam causing an inaccurate focus along the path of travel.

[farnz]

2 hours ago, geotrupede said:

A calibration issue:  can it be fixed in some way, by rotating the profile of the focus within the lens? is this possible at all?

No, unfortunately I think you'd need to have the lens's helicoid reshaped over the close focus portion where the focussing errors are occurring.

However, since it's close focus that's causing a problem I assume you're using the Visoflex 2 (or the LCD) to focus so I'm confused how you're getting focussing errors because the Viso and LCD will give you direct WYSIWYG focussing feedback. 

If you're using the OVF to focus closer than 0.7 metres then you will get errors because the OVF won't focus closer than about 0.7 metres.

Pete.

[Pintpot]

11 minutes ago, farnz said:

 

However, since it's close focus that's causing a problem I assume you're using the Visoflex 2 (or the LCD) to focus so I'm confused how you're getting focussing errors because the Viso and LCD will give you direct WYSIWYG focussing feedback. 

 

Pete.

+1 on that, and focus peek, works on IR also (as I've just found out) Can even use R zoom lens on M246 now.

[250swb]

As said before use the LCD or a Visoflex. It opens up a far larger number of possibilities than limiting yourself to the lenses that will focus accurately in the optical viewfinder, and especially if you need to use an adapter. 

Edited May 1, 2023 by 250swb

[geotrupede]

Yeah thanks all. I know about the EVF as that is why I did not realise of the issue earlier 😉

I was really hoping the assembly allowed some form of adjustment, but sounds like I will need to ask the maker for a fix ;-(

G.

 

[Ecar]

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Good luck with that... I own several MS lenses and nearly all of them needed at least one trip back to Japan and/or to a 3rd-party technician to focus properly. Since Miyazaki does calibration by the eye, this is to be expected more often than not.  

To avoid frustration, my suggestion is to send it straight away to a 3rd-party technician. As an added bonus, he will probably also remove the metal scraps left by the machining process inside the helicoid that Miyazaki doesn't seem to be bothered to clean up anymore...

Although I often wonder why I still buy MS lenses, I also have an Apollon 36/1.3 on its way to me.

Edited May 1, 2023 by Ecar