Help! 21 SEM 3.4 issue with focus?

[nameBrandon]

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Hey all.. I have a used 21 SEM I picked up recently, and I suspect something may be happening optically with the lens that is not as it was from the factory. Before I send it out for a CLA hoping that resolves the issue, I wanted to get your take on this, as I've never owned a 21 SEM before. From my understanding, this is one of the sharpest lenses Leica makes. In some instances, I am seeing very sharp results, but not across the frame in every scenario. I also recognize that accurate focus may cause some issues, but I had assumed the DoF would compensate for this, resulting in a pretty generous sharp / in-focus range. I'm also including a reference image from a Zeiss 21 2.8 from Lens Rentals (who typically tests their lenses and keeps them in good shape).

The scene is below. Shot on a tripod, 2-second timer, each lens shot at f/3.4 and f/8. Distance was just over MFD, roughly 30 inches , or 0.76m. I did my best to make sure alignment between sensor and wall was parallel. I took two shots at each aperture. I'm sharing the best and worst image for the SEM 21 when shot at f/3.4. By f/8 on the Super Elmar, the DoF seems to have covered up any issues, so only one image for SEM 21 @ f/8.

There was not that much variation in the images from the Zeiss 21 to make it worthwhile to choose a best and worst. The zoomed in images are all 100% crops.

Focusing was done exclusively via Visoflex 2, not the rangefinder patch. For each aperture, I racked focus between the shots and attempted to get the best in focus image I could at 100% magnification.

 

I've also included a link to the DNG files here

Please let me know what you think and if you feel this is appropriate performance for a properly functioning 21 Super Elmar 3.4.

Thank you!

 

Full Scene

(the 3 red boxes highlight areas of interest)

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Center / Chart @ f/3.4

SEM "Best" (f/3.4)

(Note the sharp 16:9 across bottom left and right)

SEM "Worst"  (f/3.4)

(Note the sharp left 16:9 text vs softer right "16:9" text)

 

Zeiss 21 2.8 "Best" (@3.4)

 

 

 

Center / Chart @ f/8

SEM "Best" (f/8)

 

Zeiss 21 2.8 "Best" (@f/8)

 

Test Right @ f/3.4

SEM "Best" (f/3.4)

SEM "Worst" (f/3.4)

 

Zeiss 21 2.8 "Best" (f/3.4)

 

 

Test Right @ f/8

SEM "Best" (f/8)

 

Zeiss 21 2.8 "Best" (f/8)

 

 

 

Test Left @ f/3.4

SEM "Best" (f/3.4)

 

 

SEM "Worst" (f/3.4)

 

Zeiss 21 2.8 "Best" (f/3.4)

 

Test Left @ f/8

 

SEM "Best" (f/8)

 

 

Zeiss 21 2.8 "Best" (f/8)

 

Edited December 1, 2023 by nameBrandon
clarified focusing approach

[olgierdc]

In my opinion, three photos are blurry. I looked at the DNG images. You wrote that the photos were taken on a tripod, but the yellow cards with inscriptions have blurred inscriptions. Maybe the shutter or the tripod with the shutter is causing the vibration. Place a glass of water on the camera and see if the water vibrates during the trigger.

If you have a flash, try a shorter time. ISO 200 or 400 will be sufficient.

Edited December 1, 2023 by olgierdc

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[nameBrandon]

4 minutes ago, olgierdc said:

In my opinion, three photos are blurry. I looked at the DNG images. You wrote that the photos were taken on a tripod, but the yellow cards with inscriptions have blurred inscriptions. Maybe the shutter or the tripod with the shutter is causing the vibration. Place a glass of water on the camera and see if the water vibrates during the trigger.

I agree, some of the blur on the SEM looks like motion blur, but I'm not convinced myself.. I'd be curious to know which image specifically you're looking at where you see this.. that was my first assumption, but if you look at the center of the images, I don't believe the motion blur is there. I would think the motion blur should be consistent across the frame, and not just localized to the edge..correct?

Edited December 1, 2023 by nameBrandon

[olgierdc]

I see double, thicker lines in the letters (stickers). E.g. ZM 21 3.4 Best or SEM 3.4 Worst.

 

Edited December 1, 2023 by olgierdc

[nameBrandon]

38 minutes ago, olgierdc said:

I see double, thicker lines in the letters (stickers). E.g. ZM 21 3.4 Best or SEM 3.4 Worst.

 

Agreed, I see it as well.. just not sure why that wouldn't be a uniform motion blur across the center as well..

I think my biggest concern is the center chart on SEM 3.4 Worst image.. the left 16:9 text is very sharp and clear, but only 10-12 inches to the right the other 16:9 text gets soft. I'm not sure even motion blur would explain that.  and I would think DoF would be thicker than that piece of paper and should accommodate for any slight misalignment between the camera sensor plane and the document.

 

 

 

 

Edited December 1, 2023 by nameBrandon

[NigelG]

I bought a used 21 SEM from Leica Manchester (Stevens’ as was) and struggled with focus. I did similar tests using multiple printed resolution targets as I felt the lens was probably de-centered and sent them the files.
They sent the lens back to the “mothership” and it was returned with paperwork stating that the “front element” had been changed/repaired. 
I don’t know if that meant they actually changed the front group or just re-centered it but the lens as returned was absolutely sharp across the board (and Manchester Leica won a big 👍🏻 from me.)

[nameBrandon]

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14 minutes ago, NigelG said:

I bought a used 21 SEM from Leica Manchester (Stevens’ as was) and struggled with focus. I did similar tests using multiple printed resolution targets as I felt the lens was probably de-centered and sent them the files.
They sent the lens back to the “mothership” and it was returned with paperwork stating that the “front element” had been changed/repaired. 
I don’t know if that meant they actually changed the front group or just re-centered it but the lens as returned was absolutely sharp across the board (and Manchester Leica won a big 👍🏻 from me.)

Thanks.. sounds very similar.. I hope it was just recentered.. I'm about to sent it out to YYe for CLA, but I don't think he's going to replace the front element for me.

[jaapv]

If you get inexplicable blur, try and use electronic shutter and use the self-timer 12 seconds when on a tripod; 2 seconds is insufficient to dampen vibrations.

[Kl@usW.]

I have a SEM 21 mm, bought second hand, as mint, never opened and after two or three years it got the "wobble". What happened was the front element in its housing of the helicoid got loose. Since it was out of warranty, I sent it to an experienced and well known Leica specialist who told me: the lens probably had never been opened before, the front element got loose and developed some play. Fix was very easy and fast--but didn't last too long.... after another year same problem. This time I sent it to the CS Wetzlar --they fixed it  ( 3 months turn over ) for free..... 

Could it be that you have a related problem with your copy?  An optic cell that is loose, might  produce the kind of thing you are describing.    Seems not to be  rare... if you search a little bit, you'll find some reports of wobbly front elements--most of them SEM 21. 

K. 

btw: none of your pictures is visible.