Overthinking Close Focus, Leica M5

[bob4kacz]

Hi All,

I've been troubleshooting a close-focus issue on my Leica M5 and wanted to share what I've found and get everyone's thoughts on this.

The camera was recently CLA'd by DAG, but close-focus accuracy has still been a concern. He confirmed nothing is wrong, although when I got it back the Horizontal Adjustment was off and I needed to adjust myself.

To clarify I am working with a Voigtländer Nokton V1 1.5 50mm lens. I've confirmed that infinity focus, after adjustment, is correct on my lens by testing my camera with a 50mm Summicron from a local camera shop and comparing my lens their own Leica M3.

I took a test shot at 0.9m (the lens's alleged minimum focus distance) and while it looked acceptable, it wasn't as sharp as I'd expect, photo attached. To investigate further, I removed the focusing screen from my Visoflex, taped it to the back of the camera body on the 35MM rails, set my camera on a tripod, and used it to visually confirm focus at various distances.

What I found: the image was sharpest when the lens was set to 2 feet, not the expected 0.9m (~3 feet) when looking through the focusing glass, I measured from the Focal Plane mark. This suggests to me that the lens is front-focusing at close distances and focus through is off. This doesn't seem right to me since the lens is not supposed to focus that closely. Am I overthinking this?

 

[brbo]

What I found: the image was sharpest when the lens was set to 2 feet, not the expected 0.9m (~3 feet) when looking through the focusing glass, I measured from the Focal Plane mark. This suggests to me that the lens is front-focusing at close distances and focus through is off. This doesn't seem right to me since the lens is not supposed to focus that closely. Am I overthinking this?

If lens is not supposed to focus closer than 0.9m, how are you then setting it to 2 feet?

 

[bob4kacz]

If lens is not supposed to focus closer than 0.9m, how are you then setting it to 2 feet?

I have the lens at its closest focus setting, then I am physically moving the camera and lens to my target until the image is in focus on my focusing glass, it just happens that its 2 feet when in focus.

 

[Coldkennels]

Do you have another lens to test on the M5 in a similar fashion?

My gut feeling is that your Nokton is out of spec and needs calibration, but it's entirely possible your DIY horizontal adjustment has screwed up the close focus - and without the proper tools to check it, the only DIY method is to have a "known good" lens to compare it to. Without that, there's no way of knowing if it's the Nokton or the M5 with the problem.

 

[brbo]

I find it hard to believe that Nokton would be so much out of calibration that at close focus hard stop (3 feet) it would be front focusing by a feet, but would be ok at infinity hard stop. If you've confirmed that lens set at infinity gives sharp pictures on film that means that flange distance is OK (no surprise I guess since it was just services by DAG).

Your attached shot shows front focus, but I don't think it's front focused by a feet. Are you sure that when you are checking the focus with focusing screen nothing is amiss? Focusing screen must sit on the inner film rails. The outer rails are higher and focusing screen sitting on those outer rails would show front focusing. It would also show front focus at infinity, but maybe you just think that infinity is in focus when it actually isn't?