90mm Summicron-M (e55) persistent backfocus

[mgermana]

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I've been happily shooting my M240 with 50 Summilux ASPH and 35 Summicron ASPH lenses for over two years without any problems focusing. Then I purchased a 90 Summicron-M type 3 (e55) that a) wouldn't focus to infinity and b) back-focused at every distance up to infinity. Not a little back-focus, either. I mean like four inches at the minimum focal distance! So I sent both off to DAG for adjustment. Don reported that the camera's rangefinder was slightly out of alignment and that the lens was "out more than the camera." Imagine my surprise, then, when, upon their return, I mounted the 90 to the M240 and it was as though I never sent them to be adjusted! 

I sent a message to Don to ask his advice, but that was Friday afternoon. So while I await his reply I thought I'd ask: am I overlooking something obvious? Is this a particularly troublesome lens to calibrate to digital specs? 

FWIW, when I mount the camera to a tripod and focus using LiveView, the point of focus is tack-sharp at f/2. But when I look through the OVF after taking the picture, I see two images that do not coincide at the point of focus.

I'm baffled! So any light you can shed on this mystery will be greatly appreciated!

[tgray]

Does it focus at infinity (with Live view)? If it does, is it pretty close to infinity on the distance scale on the lens?  Ignore the RF for this. If the answers to the above are yes, then it’s possible your camera is out. 
 

However, if your other lenses are fine, and you can’t hit infinity on the 90 at all, sounds like the lens is out of whack. 

[mgermana]

18 minutes ago, tgray said:

Does it focus at infinity (with Live view)? If it does, is it pretty close to infinity on the distance scale on the lens?  Ignore the RF for this. If the answers to the above are yes, then it’s possible your camera is out. 
 

However, if your other lenses are fine, and you can’t hit infinity on the 90 at all, sounds like the lens is out of whack. 

It does focus at infinity with LiveView. But the rangefinder shows two images that won't coincide. The rangefinder doesn't go *past* infinity; rather, it never reaches it.

At the same time, my 50 Lux is fine on the M240: I can focus it wide open at ~6 feet and be right on; the 90 at the same distance is back-focussed by 3-4 inches (see attached).

I think I'm back to square one...

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[adan]

35 minutes ago, mgermana said:

It does focus at infinity with LiveView. But the rangefinder shows two images that won't coincide. The rangefinder doesn't go *past* infinity; rather, it never reaches it.

Good first test.

Now - what do your 50mm and 35mm do using the same test and an "infinity" subject (at least 1000 yards/meters distant)?

If all your lenses never quite reach infinity alignment with the rangefinder, then it is the rangefinder that probably needs an adjustment. If only the 90 fails the test, and the others "reach" all the way to coincidence at infinity setting, then that lens needs adjustment.

It's perfectly possible - I have a back-focusing extremely early (1980 - so early that it is an E49) example of the compact 90 Summicron-M v.3 that is at Leica USA right now, to fix a real back-focus error (as well as receive 6-bit coding). 40 years of wear-and-tear can do that.

But it should be remembered that a Leica RF has a fixed precision that is vast overkill for shorter focal lengths - the larger depth of field with 50 or 35mm lenses may hide a camera/rangefinder problem that only the long, fast 90's very narrow DoF will make obvious.

So "it focuses with my 50 and 35, but not with my 90" is pretty subjective - check the rangefinder at infinity with all the lenses.

[mgermana]

1 hour ago, adan said:

Good first test.

Now - what do your 50mm and 35mm do using the same test and an "infinity" subject (at least 1000 yards/meters distant)?

If all your lenses never quite reach infinity alignment with the rangefinder, then it is the rangefinder that probably needs an adjustment. If only the 90 fails the test, and the others "reach" all the way to coincidence at infinity setting, then that lens needs adjustment.

It's perfectly possible - I have a back-focusing extremely early (1980 - so early that it is an E49) example of the compact 90 Summicron-M v.3 that is at Leica USA right now, to fix a real back-focus error (as well as receive 6-bit coding). 40 years of wear-and-tear can do that.

But it should be remembered that a Leica RF has a fixed precision that is vast overkill for shorter focal lengths - the larger depth of field with 50 or 35mm lenses may hide a camera/rangefinder problem that only the long, fast 90's very narrow DoF will make obvious.

So "it focuses with my 50 and 35, but not with my 90" is pretty subjective - check the rangefinder at infinity with all the lenses.

Thanks for this. I tested the other lenses, and they do reach all the way to coincidence at infinity. Which suggests that the lens is out of whack.

DAG said he adjusted both--a minor adjust for the M240 and a more significant one for the 90--but they seem the same as before I sent them. DAG's work speaks for itself, but I can't understand how both body and lens could be adjusted by him and still function the same as before. Please tell me there's something obvious I'm overlooking...

Edited September 26, 2020 by mgermana

[mgermana]

Here's a crop from the image above. Note that I have focused the rangefinder on the front corner of the box, not the "Leica M" to the left...

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Edited September 26, 2020 by mgermana

[mgermana]

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...and here's another crop of a photo taken from the same distance with my 50 Lux at f/1.4. Same point of focus (the front edge of the box).

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Edited September 26, 2020 by mgermana

[tgray]

This DIY target was useful in dialing things in for me. And finding that for sure, my 90/2 and 90/4 macro were not in sync. So maybe my RF was out, but at the very least, one of the lenses was too. 
 

http://www.squit.co.uk/photo/focuschart.html

[jaeger]

I had 18 months of fun fixing a similar issue.  Do you remember you had the camera, 50mm and 35mm sent to somewhere for calibration before?  If you did where did you sent to?

Edited September 27, 2020 by jaeger

[mgermana]

8 hours ago, jaeger said:

I had 18 months of fun fixing a similar issue.  Do you remember you had the camera, 50mm and 35mm sent to somewhere for calibration before?  If you did where did you sent to?

I’ve never had any of my Leica gear calibrated—it all just worked together from the start. Granted, the 35 could be way out and I’d never know it. But the 50 Summilux, which I commonly shoot wide open, is somewhat less forgiving, and it’s been fine. 

This being said, I can see how the 35 and the 50 could be within the rangefinder’s tolerances and the 90 outside of them. But that’s why I sent both the camera and the lens to DAG and paid to have them both adjusted: I wasn’t sure if one or the other or both were out of alignment. 

The source of my confusion—and frustration—is that I’m no closer to figuring this out than I was before. If the M240 and the 90 Summicron won’t play nice together after the best repairman in the US has adjusted them, then how am I going to get them to work with one another?

[mgermana]

Here's a quick shot of the infinity adjustment and focus throw adjustment in my M240. Anything look weird or out of place to you?

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[mgermana]

Here's a possible clue (and thanks for bearing with me). The amount of back-focus increases as distance to subject increases, but only with the 90. At minimum focal distance, the amount of back-focus is between half and inch and an inch. At 10ft, the back-focus is nearly a foot. This is not the case with my 50, at least as far as I can tell. I can't tell shots taken with LiveView apart from ones taken with the rangefinder when the 50 is mounted.

Edited September 27, 2020 by mgermana

[jaeger]

1 hour ago, mgermana said:

If the M240 and the 90 Summicron won’t play nice together

I can ensure you that it's not true.  The m body will work with any M lenses from LTM to today most recent design without any focus issue.  The "rate of change" on both lens and body need to match nothing rocket science there. 

If I were you, I will documented near, mid and infinity on tripod for all lenses - apertures wide open.  Create folders in your lightroom on each test. 

 

1 hour ago, mgermana said:

Here's a quick shot of the infinity adjustment and focus throw adjustment in my M240. Anything look weird or out of place to you?

It looks almost identical to mine.  A tad of adjustment on these screw is night and day, and once you start poking it you will have sleepless nights for weeks or months.  But once you figure them out you know a lot about rangefinder. 

 

2 hours ago, mgermana said:

I’ve never had any of my Leica gear calibrated

Did you buy them new or you bought them used?  If used, did the acquired from the same person?  I am asking because there might be some histories.

 

[mgermana]

6 minutes ago, jaeger said:

I can ensure you that it's not true.  The m body will work with any M lenses from LTM to today most recent design without any focus issue.  The "rate of change" on both lens and body need to match nothing rocket science there. 

If I were you, I will documented near, mid and infinity on tripod for all lenses - apertures wide open.  Create folders in your lightroom on each test. 

 

It looks almost identical to mine.  A tad of adjustment on these screw is night and day, and once you start poking it you will have sleepless nights for weeks or months.  But once you figure them out you know a lot about rangefinder. 

 

Did you buy them new or you bought them used?  If used, did the acquired from the same person?  I am asking because there might be some histories.

 

I purchased all my Leica gear used, and each item came from a different seller/source. So whatever histories there are, they’re mysteries to me!

[mgermana]

Here are some striking test results. I put the camera on a tripod and shot a target at 10ft and 25ft, first with the 50 Lux ASPH wide open, and then with the 90 wide open. These are all shot with the rangefinder, not with LiveView! These are all crops of between 100-300%. Here's the 50 at 10ft:

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Edited September 27, 2020 by mgermana

[mgermana]

The 50 at 25ft. This is about a 300% crop: 

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[mgermana]

Now the 90 at 10f--actually slightly front-focusedt: 

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[mgermana]

And finally, the 90 at 25ft. Badly back-focused!

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[jdlaing]

1 minute ago, mgermana said:

Now the 90 at 10f--actually slightly front-focusedt: 

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What aperture setting?

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[mgermana]

1 minute ago, jdlaing said:

What aperture setting?

Wide open for both lenses: 1.4 for the 50, 2.0 for the 90.