Is it normal for an older Leica lens to not have precise spot on infinity focus?

[A miller]

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I have just happened to realize that my 50mm DR summicron and 28mm elmarit pre-asph ver iv do not focus exactly spot on at infinity.  Rather, they go very slightly beyond infinity.  I have made this conclusion based on a controlled experiment whereby I tested all of my lenses and two film cameras.  All of my other 3 leica lenses (75mm lux, 35mm lux asph fle and 50mm lux asph focused spot on at infinity on both cameras.  The 50 DR and 28mm went slightly beyond infinity on both cameras.  I called Youxin Ye and asked him about this and he said that it is quite normal for Leica lenses of these vintages to not only have these slight deviations, but to come out of the factory with them; and that this is normal and it CANNOT be adjusted to focus spot on at infinity.  He said that when these lenses were made there was only film photography and the tolerance levels were so much greater than any deviations that the deviations won't matter at all to the images, provided that they are with film.

 

Any one care to confirm or deny this theory that the slight deviation (and I am talking very slight) is normal and not something that can be perfected?

 

Many thanks, 

Adam

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[jdlaing]

I have just happened to realize that my 50mm DR summicron and 28mm elmarit pre-asph ver iv do not focus exactly spot on at infinity.  Rather, they go very slightly beyond infinity.  I have made this conclusion based on a controlled experiment whereby I tested all of my lenses and two film cameras.  All of my other 3 leica lenses (75mm lux, 35mm lux asph fle and 50mm lux asph focused spot on at infinity on both cameras.  The 50 DR and 28mm went slightly beyond infinity on both cameras.  I called Youxin Ye and asked him about this and he said that it is quite normal for Leica lenses of these vintages to not only have these slight deviations, but to come out of the factory with them; and that this is normal and it CANNOT be adjusted to focus spot on at infinity.  He said that when these lenses were made there was only film photography and the tolerance levels were so much greater than any deviations that the deviations won't matter at all to the images, provided that they are with film.

 

Any one care to confirm or deny this theory that the slight deviation (and I am talking very slight) is normal and not something that can be perfected?

 

Many thanks, 

Adam

Are you talking about taking the lens all the way to infinity against the stop or infinity lining up the infinity mark?

 

I know in older lenses I have used and owned that the stop is actually slightly past infinity. The old trick in focusing to infinity used to be taking it to the stop and backing off slightly.

[A miller]

thanks, JD.  

Sorry for not being clear.

For the two suspect lenses, when I turn the focusing ring all the way toward infinity until it cannot go any more, the focus goes beyond infinity and I need to turn very slightly the other way to line up the focusing patch to infinity.

Does this jive with your past experience and have you deemed this to be normal?

[jdlaing]

thanks, JD.  

Sorry for not being clear.

For the two suspect lenses, when I turn the focusing ring all the way toward infinity until it cannot go any more, the focus goes beyond infinity and I need to turn very slightly the other way to line up the focusing patch to infinity.

Does this jive with your past experience and have you deemed this to be normal?

Yes it does. I found that the more wear and tear on a lens will take it farther past infinity when up against the stop.

My newer lenses, and I don't know if this is on purpose from Leica hit focus at infinity at the stop.

[A miller]

very interesting.  thanks for the input.

Is this something that can be corrected through an adjustment?

Youxin didn't seem to think so but I wonder what others have experienced...

[jdlaing]

very interesting. thanks for the input.

Is this something that can be corrected through an adjustment?

Youxin didn't seem to think so but I wonder what others have experienced...

I asked one time a long time ago and got a no answer. Things may have changed since then.

 

One other thing I got used to is when hitting the stop and then backing off slightly I got used to the amount of back off depending on the lens. The tighter the aperture the less I had to back off as the dof was greater.

 

My Canon RF lenses showed greater wear and so did my Olympus OM. The Leica not so much.

[Lenshacker]

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My 1950s M-Mount Collapsible Summicron, Summarit-M, and Type 1 Rigid Summicron do not have this issue. I can imagine the DR might be more finicky due to the more complex Dual Cams.

 

If it is pushing the RF beyond infinity, it is pushing in too far. This means the cam of the lens has shifted somehow.

 

Does the actual focus of the lens agree with the Rangefinder or does it agree with the distance scale? If the RF gets pushed past infinity, and the actual focus agrees with the camera's rangefinder: the position of the Cam is off.

[A miller]

Thanks, Lenshacker.  The focus ring does NOT move past the infinity marker.  It is just that infinity is reached just slightly before the focus ring reaches the end

[Nordvik]

I have had two new Zeiss ZM lenses that did not reach infinity. Rangefinder showed infinity at infinity mark on lens.

[250swb]

I think infinity is over rated.

 

Even wide open there should be enough DOF with most lenses that infinity shows up as sharp if the lens marking is there or thereabouts, it's the closer focusing distances that need to be accurate. For most people the perception of infinity varies vastly from reality, often it is thought of as just a bit further past the last marking on the lens barrel, so maybe 50 feet and beyond, when in truth it could be a mile away. Anyway, forty years on and I still don't know if any of my Leica lenses are precise at infinity because I have never bothered to check and don't intend to start.

 

Steve

 

[menos I M6]

It is indeed correct that this slight deviation cannot be adjusted in the lens with the 50/2 DR.

The only means to correct this is to either machine the RF cam of the lens to a more precise dimension or to source spare parts and find one that provides a better fit (which is not practical as the number of available lenses is limited, spares surely exhausted, slaughtering a donor lens would be excessive and most importantly this is not an issue with a 50mm lens.

 

It can be an issue with very fast longer lenses, where infinity is NOT the issue (as you simply set focus at the infinity stop) but distances just in front of infinity, when focussing with the rangefinder. With a 50/2 lens these distances will easily be covered by DOF to not be visible.

 

Use your lens as it is - it's a fine lens ;-)

[A miller]

Many thanks, Steve, Dirk and Nordvik - i really appreciate your insights. So long as no red flags should be raised about this, it is hard for me to find the energy to fuss about it.

[Nordvik]

Before/After:

 

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[Nordvik]

Another before/after. This time at 5,6. First one was at 2,0. After at 2,0 is as good as before at 5,6.

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[Susie]

I wouldn't worry sbout it! 

 

Unless the lens has been used all day, every day by a professional press snapper, or has suffered a heavy knock, just trust the lens to do its job.  Take some pictures and if they show up an obvious defect in the focussing then get it checked out. I emphasised the focussing, as you need to make sure there is no camera shake etc. when you're testing it.

 

I have some pretty old lenses, some of which have had a hard previous life, but even they have always focussed accurately.  Of course as soon as you start to zone focus for depth of field, you just have to trust the markings on the lens anyway.

 

At the end of the day, if the lens gives you the image you are after, then it is working just fine.

 

As for the Zeiss lenses not being accurate - well that is why I've used  Leica cameras and Leica lenses for thirty years!  But then if it has an LTM mount and an aftermarket M adapter, who knows where the error is?

 

Susie

[spydrxx]

Just a reminder about what the character of infinity is in the lens world vs our other conceptions. Optical infinity is usually described at 1000 x the focal length of the lens. Having said that, whenever I touch up any of my rangefinder cameras, I typically select a much greater distance and let DOF take care of the difference. BTW, when I had an issue similar to yours, and I sent the lens to Youxin Ye for a CLA due to some internal haze, we discussed the issue of actual infinity focus vs the marking on the lens barrel, and he very patiently explained the various reasons they might not exactly coincide. My obsessive scientifically trained mind didn't want to fully accept his explanation, but over time, practical results seem to bear it out.

[A miller]

Many thanks Susie and Spydrxx.  Very helpful insights. 

[CheshireCat]

Before/After:

 

Before/After what ?

 

My Summicron-M 75 goes beyond infinity. Results wide open are noticeably worse with the focus ring set at "infinity", and I need to stop down a or use the EVF. for sharp results.

All my canon lenses go beyond infinity, but AF does its job.

If I only had an M9 (no Live View), I would have returned the lens.

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[Susie]

 

 

"My Summicron-M 75 goes beyond infinity. Results wide open are noticeably worse with the focus ring set at "infinity", and I need to stop down a or use the EVF. for sharp results."

 

Are you saying that when you focus using the coupled rangefinder and then look at the live view, the sharp focus is somewhere else?  If that really is the case then the lens is faulty and must have been damaged somehow. 

 

If you are estimating how far away infinity is and then setting the scale,  then I think you're on a bit of a sticky wicket.  I remember reading somwhere (it  might have been Osterloh's book) that Leitz used the highest number the computer would handle when it comes to infinity, rather then the more usual umteen times the focal length.

 

Of course when using film one doesn't have the 'luxury' of checking the focus on a screen before taking the shot, and I doubt that the screen on my M9 is good enough either. I just use the latter to check overall composition.

 

 

 

But then, as I said above, I just trust the engineering, bumble about, and am happy if something comes out at all!  But I have never had problems with things not being in focus.

 

Susie

[Nordvik]

Before/After what ?

 

 

Repair.