Black stripe when adapting vintage lens

Hello everyone,

I bought a Helios 44 in M39 mount to adapt to my EOS R. I adapted it using the recommended technique I found online (ie : Soviet 16.4mm extension tube + Leica M39 to EOS R adapter). It works well, and I have no issue with the focus at infinity, but... on some images, I get a very clear dark stripe on one side of the image that has no explanation in the scene I'm photographing (see examples below). It's not on all pictures, and it doesn't seem to be linked to the aperture I use. It does seem to appear more often when I use the camera on vertical, though. So if you guys have any idea where that might be coming from, I'd be grateful to know !
It's not too much of an issue, since a graduated filter in Lightroom generally gets rid of it, but still, I'm curious.
Thank you beforehand !
Yael

What's your shutter set for -- mechanical, electronic, etc.???

xkaes said:

What's your shutter set for -- mechanical, electronic, etc.???

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Mechanical, always. I've had issues with the electronic shutter indoors a long time ago (with tungsten light), and I swore never to use it again ^^.

I would guess that something in the adaptation has moved the light path off centre.

MattKing said:

I would guess that something in the adaptation has moved the light path off centre.

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I guess it's possible, but I really can't see what. The M39 adapter is a perfect fit, and the extension tube is just a hollow metal ring, and the screw mount is in a good shape. So I can't see what would throw the light path off center. It also doesn't explain why it's not a consistent "bug", and only appears on some images, don't you think ?

Yaeli said:

I guess it's possible, but I really can't see what. The M39 adapter is a perfect fit, and the extension tube is just a hollow metal ring, and the screw mount is in a good shape. So I can't see what would throw the light path off center. It also doesn't explain why it's not a consistent "bug", and only appears on some images, don't you think ?

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If any of the adapter components are bent, the plane of focus would be askew, and the image would be displaced from centre.

MattKing said:

If any of the adapter components are bent, the plane of focus would be askew, and the image would be displaced from centre.

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Yes, that makes sense. But I don't understand why it wouldn't appear all the time. Anyway, it's not too big of a deal. I guess I'll just keep adding a graduated filter when needed. Thanks anyway !

Yaeli said:

Yes, that makes sense. But I don't understand why it wouldn't appear all the time. Anyway, it's not too big of a deal. I guess I'll just keep adding a graduated filter when needed. Thanks anyway !

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Is thewre any correlation between the effect and a particular range of shutter speeds?

MattKing said:

Is thewre any correlation between the effect and a particular range of shutter speeds?

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It seems to appear only above 1/3000 of a second (the two examples I showed were at 1/4000 and 1/6000). But I also have other images shot at those shutter speeds that don't show that dark stripe, so I don't know.

It's more than a dark stripe - there is an area of about 20% of the frame that is darkened on the right side. But you are holding the camera sideways to shoot vertical, so it's actually receiving less light across the bottom 20% of the sensor, right? Try shooting a vertical by holding it the other way, just to confirm which part of the sensor is being affected by less light. And switch between mechanical and electronic shutter and keep notes. Could be the mechanical shutter is not moving at an equal speed across the entire sensor at some shutter speeds.

Have you proven the camera can make normal images with some other lens?