Lens Problem / split-image stalls for abit

[Tytan]

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Am experiencing a problem with my lens (50mm Summilux BP)

 

I rotate the focusing ring to the shortest focus distance, all the way till the hard stop.

Then as I very slowly turn the focusing ring anti-clockwise (to lengthen the focus distance), the split image in the focusing rectangle doesn't move for the first few millimeters of the turn ... and only starts moving/aligning as i continue turning.

 

What could be the cause of this?

 

I put on another lens onto the same camera body, and all's good .. so i'm guessing the body's fine(?)

 

 

 

 

[spydrxx]

Do you notice a tactile "bump" thru your fingers when focusing. If so, it probably is the lens. However I'm more inclined to believe there may be some dust, or dried particulate matter, in the RF mechanism itself, which after you have the initial problem and then switch lenses, has loosened.

[pop]

When mounting the lens to the body, you must have seen the smallish roller at the 12 o'clock position within the throat of the camera. The lens presses this roller into the camera when focusing at infinity. Focusing closer will move the optical elements of the lens forward, away from the camera body. The roller will track the movement by following the lens. It is spring-loaded. It's this movement of the roller arm which moves one of the images in the rangefinder.

 

The optical parts in your 50mm Summilux seem to move a tiny bit farther from the camera body than the roller can follow. The roller will just go as far as it can. This is when focusing still closer has no effect on the rangefinder.

[TomB_tx]

The cam follower arm also has an adjustable stop that keeps it from moving too far out with no lens attached. When my M6 had A CLA it would not focus as close as before, because the stop in the body was adjusted differently. I later sent the body to DAG (not the tech who did the CLA) who corrected it.

[Tytan]

Thank you spydrxx, pop, Tom for your replies.

 

I do hear, AND feel, a very soft (almost unnoticeable) click coming from the lens when focusing around the minimum focus distance, I'd say around when the split image doesn't move.

Also, when I gently shake the lens, I hear a rattling sound.

 

Will this stalled split image problem throw off the entire focusing range of the lens? I don't have my digital M body with me to test this with.

 

This morning, I put on a 75mm cron onto the same body, and no issues at all.

[pop]

There's one way to tell (short of sending it in): take a few shots with the aperture wide open at 1 and 5 meters each, with different lenses. Use something simple as a target, such as a focus test chart. Then you'll see in a moment whether the lens focuses reasonably well over its range. 

[Tytan]

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So i brought the lens back to the shop i purchased it from.

Upon describing the issue, the shop owner immediately knew what i was talking about.

He took out another 50mm Summilux BP (same as the one I have), and another 'older' lens (i don't remember which one), and they both exhibited the same condition.

Apparently these lens were made such that there have more 'give' beyond the shortest 'marked' minimum focus distance.

 

Can anyone else confirm this, or provide more insights into this?

I'm not 100% convinced at this point.

 

 

[spydrxx]

Ah, now I am clearer on what you are talking about. While I can't speak for Leica lenses, I have some other lenses (for Leica bodies) which have a minimum focusing distance shorter than the RF mechanism provides for, and in which case the user must either be using them on a digital body with live view or an analog body with a tape measure. There is a "bump" at the crossover point to let you know that you have exceeded the point where the rangefinder is accurate. Hope this provides some insight.