Leitz Summar 50mm F/2 back focusing problem

[RussPhoto]

Hello Everyone, Just did some tests with my Leica M digital using Summar 50mm on wide open at F/2 from the distance of 3.5 ft. and found out that it’s back focusing (see image attached) Turning focusing wheel to the left a bit about 1 or 2 mm correct the problem (right side image looks sharper). Even shooting at F/3.2 it’s still back focusing a bit… I’m using genuine Leica LTM to M adapter so shouldn’t be an issue. I know Zeiss Sonnars has similar problem but I didn’t expect it with Summar. Or maybe this is just my copy has that problem? Is it common, anyone had a similar experience?? Thank you!

 

[Sonnar Brian]

Mine is spot-on, wide-open, on my M9. Something is off on yours.

 

[Coldkennels]

Mine is also absolutely bang-on wide-open on both LTM bodies and my M240. In fact, it's the most reliable lens that I own:



At the risk of stating the bleeding obvious: is the lens definitely fully extended and locked in position? And is your M focusing correctly with another "known good" lens? It could just be that your rangefinder is off.

 

[RussPhoto]

Mine is also absolutely bang-on wide-open on both LTM bodies and my M240. In fact, it's the most reliable lens that I own:

View attachment 4858078

At the risk of stating the bleeding obvious: is the lens definitely fully extended and locked in position? And is your M focusing correctly with another "known good" lens? It could just be that your rangefinder is off.

My camera works fine with another LTM lenses. All images taken at infinity are okay with Summar, all is sharp, only at close range it's back focusing

 

[Sonnar Brian]

It sounds like someone replaced a lens element/group and now the focal length is off.
These lenses were "fit and Finish", take a part, fit it on, test the outcome, and adjust a little.
I know, because I replaced the front element on the Summar that I used for the example.

 

[RussPhoto]

It sounds like someone replaced a lens element/group and now the focal length is off.
These lenses were "fit and Finish", take a part, fit it on, test the outcome, and adjust a little.
I know, because I replaced the front element on the Summar that I used for the example.

It works okay at infinity and images are sharp, may be I over tightened front glass after cleaning, now aperture dot is offset a bit. I'll try to inline it with F/2 see what happen

View attachment 4858085

 

[Sonnar Brian]

That is not far off enough to cause the problems you are seeing.
Did it focus correctly before cleaning it?

 

[RussPhoto]

It sounds like someone replaced a lens element/group and now the focal length is off.
These lenses were "fit and Finish", take a part, fit it on, test the outcome, and adjust a little.
I know, because I replaced the front element on the Summar that I used for the example.

May be it's a little bit better after in lining aperture dot but still it's back focusing, have to turn focusing wheel a bit to the left to get good sharpness (see attached)

 

[RussPhoto]

That is not far off enough to cause the problems you are seeing.
Did it focus correctly before cleaning it?

Unfortunately I didn't check it before cleaning.

 

[Sonnar Brian]

If the focus is good at infinity at F2, but back-focuses when used close-up- that means the lens is too close to the image plane when used close-up. This always makes my head hurt, but that will happen when the focal length is too long. Check that all of the glass is in tight.

 

[Richard G]

My 50 Summicron did this for nearly thirty years before I picked it up. Got it fixed. Almost never take shot where it mattered.

 

[Erik van Straten]

gelatin silver print (summar 50mm f2) leica lll

J.V. 2018

 

[RussPhoto]

If the focus is good at infinity at F2, but back-focuses when used close-up- that means the lens is too close to the image plane when used close-up. This always makes my head hurt, but that will happen when the focal length is too long. Check that all of the glass is in tight.

I think I sorted out where the problem is, it's in LTM to M adapter I used. I attached the lens to LTM body and noticed that black mark indicating lens retraction is in position "noon" but on my M body it's slightly offset to the right, that's the reason I had to turn it tiny bit backward to compensate for accurate focusing. Nothing is wrong with LTM to M adapter it's just the case with this particular Summar 50mm, this adapter works fine with all my other LTM lenses. So I found another Japanese LTM to M adapter for 35 frame line and as you may see from the picture it's in "noon" position now and the problem is corrected. I also checked the lens on Sony full frame mirrorless just to make sure the lens itself is ok and all images I took were fine and tack sharp. So the problem was in LTM to M adapter for this L39 Summar 50mm

 

[Coldkennels]

I think I sorted out where the problem is, it's in LTM to M adapter I used. I attached the lens to LTM body and noticed that black mark indicating lens retraction is in position "noon" but on my M body it's slightly offset to the right, that's the reason I had to turn it tiny bit backward to compensate for accurate focusing.

None of this makes sense.

Here's where the Summar mounts on an LTM Leica:



Notice that the orientation matches the position of the lens using the Leitz-made LTM adapter in the photos above. This is the intended position of the lens.

But also, look at the back of your Summar - it's got a complete rangefinder cam (i.e. not a tongue-shaped partial one like a 135mm Hektor), and the cam isn't "shrouded" or partially blocked like the one on the 35mm f/3.5 Summaron. What this means is that rotational alignment actually doesn't matter with the Summar; it could be mounted upside down and as long as the flange-to-film distance is correct, it should focus properly using the rangefinder.

What I think is happening here is that the Leitz adapter is correct (as proved by it working with other lenses), but the Japanese-made adapter has precisely the wrong thickness, and this is compensating for an issue with the lens itself.

 

[RussPhoto]

None of this makes sense.

Here's where the Summar mounts on an LTM Leica:

View attachment 4858162

Notice that the orientation matches the position of the lens using the Leitz-made LTM adapter in the photos above. This is the intended position of the lens.

But also, look at the back of your Summar - it's got a complete rangefinder cam (i.e. not a tongue-shaped partial one like a 135mm Hektor), and the cam isn't "shrouded" or partially blocked like the one on the 35mm f/3.5 Summaron. What this means is that rotational alignment actually doesn't matter with the Summar; it could be mounted upside down and as long as the flange-to-film distance is correct, it should focus properly using the rangefinder.

What I think is happening here is that the Leitz adapter is correct (as proved by it working with other lenses), but the Japanese-made adapter has precisely the wrong thickness, and this is compensating for an issue with the lens itself.

I think I was the first one to clean the glass since 1937 when this lens was manufactured 😉 I put everything back the right way, it wasn't really hard to do, all is intact and nothing is wiggling. My guess is that the lens has a bit of back focusing? Just did few test shots at wide open and I like the lens renders

Thank you to everyone for your replies and pictures you uploaded. They all look very nice!

 

[lukx]

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Glad to hear OP is happy with his lens now.