sonnars and focus shift

[msbarnes]

I have and had some vintage sonnars (Zeiss Opton, Canon, Nikon). I mostly shot them at f2.0 - f2.4. all on film...mostly 400 speed film.

I have never an issue with focus shift at these apertures...It seems that many people notice/complain about the **** on the new ZM lenses but I read fewer "complaints" on these vintage ones, just the acknowledgement that they exist. It is also seems that most people buy the ZM sonnar to use wide open where things are inherently more problematic.

Regarding the ZM lens,

1. For those who have it optimized at f1.5, do you notice the shift at f2.0?
2. For those who are more experienced with some of the older sonnars, do you notice that some shift more or less than others?

Like I said, I don't notice shift at f2.0-f4.0 where I use these lenses most often. I don't shoot wide-open much but when I miss, it seems slight and can just be me missing from the shallow DOF.

 

[S.H.]

I use old sonnars 50 1.5 on Leica. They are good at 1.5/close range, not great at infinity, so I think they are calibrated at 1m/f1.5 and that at infinity f>5.6 DOF should take care of the rest. But they are on Contax=>Leica adapters. I used an old Voigtlander Utron and a Menopta 53/1.8 on those adapters and they were better at infinity (Ultron is Double Gauss I think and Menopta is Planar, so probably less focus shift).

Note that I'm not an expert in optics.

Between 1.5 and 2 at 1 meter, never saw a problem in my pictures. But I do not shoot USAF targets.

 

[msbarnes]

True. Actually I did notice some weird things wide open at further distances and stopped down too far, they seemed less sharp.

 

[Richard G]

I think even the f1.5 optimized copies of the ZM C Sonnar vary, judging by my lack of complaint, my formal test (http://photo.net/leica-rangefinders-forum/00aKSW) and comparison of that test with the test of one other member here (http://www.rangefinderforum.com/forums/showthread.php?t=51742&highlight=mfogiel+zeiss+sonnar). Mine seems to be optimized for about f2.2 which minimizes the amount of focus shift for all the wide apertures. I think I have had one photograph where I identified the front focus at f1.5.

 

[mfogiel]

The focus shift is most evident between f 1.5 and f 2.8, if your sonnars are slower, it might not be present at all. In old sonnars it is also less evident, because they are generally less sharp.

http://www.rangefinderforum.com/forums/showthread.php?t=51742

 

[kxl]

Regarding the ZM lens,

1. For those who have it optimized at f1.5, do you notice the shift at f2.0?
2. For those who are more experienced with some of the older sonnars, do you notice that some shift more or less than others?

As already stated it is most noticeable at the larger apertures, while at minimum focusing distances.

Back when I still had a ZM optimized for f1.5, I did a test shooting the inch markers on a yardstick at the minimum focus distance. At f1.5, the focus was spot on, but as I stopped down, the focus shift became obvious; however, as I stopped down to f5.6 or so, the increased DOF hid the focus shift.

At even greater distances, shooting at f5.6 or so, the focus shift is totally hidden by the increased DOF. It does NOT mean it's not there -- it is just hidden by the DOF.

 

[msbarnes]

The focus shift is most evident between f 1.5 and f 2.8, if your sonnars are slower, it might not be present at all. In old sonnars it is also less evident, because they are generally less sharp.

http://www.rangefinderforum.com/forums/showthread.php?t=51742

Thanks!

I skimmed over it and I think that it is very helpful.

I'll have to look into it more carefully but I think that for my shooting style. f2.0-f4.0 at a few meters, the focus shift will not be that important. This is just something i'm curious about and I'm not concerned myself with my lenses because I don't see any problems.

 

[sevres_babylone]

I shoot with an M9. I have the ZM, optimized at F1.5. I find I don't have to worry about focus shift at 1.5 or 2, but I tend now to stay away from F2.8. I also have the Canon F1.5 and have borrowed a friend's Nikon F1.4, and find that the focus shift is less noticeable. I wouldn't describe the Nikon as being less sharp than the ZM. Caution: None of my observations is based on serious, disciplined testing.

 

[Mark C]

It is easy enough to find out exactly what is going on with a particular lens and camera combination with three or four shots on a tripod. I tent to shoot a ruler laying a sheet of printed paper on my desk at about 4 feet, just because that is convenient. You could also set something up inside, or outside for moderate distance like 10 or 15 feet. It is really difficult to see what is going on beyond that distance, but the shift will be very similar to what you see in the other shots.

Digital is easy. If you are testing on film, a decent magnifier is much more useful for this than scanning or printing.

I've been considering a new Zeiss 50/1.5 so am curious about that too. My best guess is that the comment is right about it just being sharper (and contrastier), making the shift more noticeable. I'd be happy know more, or to see a comparison.

I have and had some vintage sonnars (Zeiss Opton, Canon, Nikon). I mostly shot them at f2.0 - f2.4. all on film...mostly 400 speed film.

I have never an issue with focus shift at these apertures...It seems that many people notice/complain about the **** on the new ZM lenses but I read fewer "complaints" on these vintage ones, just the acknowledgement that they exist. It is also seems that most people buy the ZM sonnar to use wide open where things are inherently more problematic.

Regarding the ZM lens,

1. For those who have it optimized at f1.5, do you notice the shift at f2.0?
2. For those who are more experienced with some of the older sonnars, do you notice that some shift more or less than others?

Like I said, I don't notice shift at f2.0-f4.0 where I use these lenses most often. I don't shoot wide-open much but when I miss, it seems slight and can just be me missing from the shallow DOF.

 

[Mark C]

Out of curiosity, I did a few quick tests on the fast lenses I have around right now (no Sonnars) and they all show noticeable shift, Most, maybe all, were double gauss Planar types. I'd never particularly noticed it in shooting, but now realize that I can get sharper images with effectively more depth of field by focusing on the front most thing I really want to be sharp, so useful to know.

BTW, I wonder how much some of the assumed differences in "optimization" would change if folks swapped lenses or bodies. I'm not doubting this varies, but I've seen very few film Leica rangefinders that seem precisely to spec. They have excess accuracy for most uses, so very slight differences are rarely noticeable except by direct comparison.

And I get the impression that "optimization" is usually taken to mean adjusted to focus best at the f/stop or distance, not actually better optically corrected for it. Any thoughts on that? Comments on the Nikkor 50 1.4 seem to imply an exception there, but I really don't know.

 

[S.H.]

(...)

And I get the impression that "optimization" is usually taken to mean adjusted to focus best at the f/stop or distance, not actually better optically corrected for it. Any thoughts on that? Comments on the Nikkor 50 1.4 seem to imply an exception there, but I really don't know.

That is what I think too.

 

[DNG]

In regards to the modern CZ-M 50mm f/1.5 Sonnar.
It was made to have a small shift closer at f/1.5 from (from 1m to about 2.5m) and optimized for f/2.8 from that distance zone.
It is well documented on the CZ website concerning the modern CZ-M Sonnar.

with RF film or w/o live view, take that in consideration from 1m to about 2.5m at f/1.5..

CZ did make (Or more correctly, Voigtlander/Cosina) a batch of the modern 50mm f/1.5 Sonnar with f/1.5 optimization because many wanted to shoot at only f/1.5 in low light.

I had that lens (f/2.8 optimized),..and on my M5, I did not really see a shift. with a few people photos.. but, I stayed within 10' of the subject, so, really no issue.
On my Pany G1, f/1.5 was Sharp, because I used Live manual focusing....

 

[Steve Bellayr]

I never had had a problem with my lens. I don't even know what it's MINIMUM FOCUS is because I do not shoot at the minimum focus. Even though I must I do not like going below f4.0. When I did shoot at wider apertures I was not at the minimum focus. For example if I am at a Jazz Club shooting the performers at an f-stop below 4 consider the difficulty. Does it matter if the exactly what is in focus? Is it the eyes or the nose? The distance is only about 2/3 inches. If you want to shoot at extreme close-ups this is no the lens for you.

 

[thompsonks]

"Mine seems to be optimized for about f2.2 which minimizes the amount of focus shift for all the wide apertures."

I bought an M-mount Sonnar here on RFF a month or so ago, supposedly calibrated for f2.8. But when I tested it I got just the same result as Richard: At closest distance and widest aperture it front-focuses slightly, but it's 'right on' at f2.2 (on M9 body). I'd intended to have it re-calibrated for f1.5, but it turned out to be just right for me. I use it at either f2, or from f5.6 to f8.

Re: other Sonnars: I have a 1938 Sonnar re-mounted from Contax to Leica by Brian Sweeney, and it's perfect at f1.5 – but unsharp at infinity. And a 5cm 1.4 Nikkor (Sonnar) that front-focuses a bit on Nikon RFs but is perfect at f1.4 on M9 (with Amedeo adapter).

IMO close-distance focus is more complicated than calibration for f1.5 or 2.8. Lens samples vary, as well as their fit to particular bodies. I have some Leica lenses that were calibrated by DAG to a particular body, but other lens/body combinations vary a bit. I have a 3x5 card that says with this body and that lens, lean forward or back a little bit. But usually I just forget about it.

Kirk

 

[FrozenInTime]

Here's how my F/2.8 optimized i.e. as it comes ZM sonnar moves in focus
0.9m measured with a tape to the 10cm mark on the scale

@f/1.5

@f/2.0

@f/2.8

@f/4.0

@f/5.6

@f/8.0

 

[Richard G]

Nice test. The focus is on '10'? Looks like the sharpest number on the ruler is between 13 and 14 at f1.5. Is the ruler at a 45 degree angle to the lens axis? If so this is front focus of 2.5cm.

And is that a second copy of Volume 51 next to Volume 80????

 

[ferider]

The modern ZM C-Sonnar has enough contrast wide open that the focus shift is easily observed.

On classic Sonnars (for example my Canon 50/1.5 and two Nikkors 50/1.4) the contrast is dramatically reduced when opening up from f2 to f1.5/1.4, so it's much harder to observe. Still it's there. My Canon is optimized for middle apertures, my Nikkors for wide open use.

Also, with the LTM Sonnars, where the shift occurs obviously depends on the LTM adapter that you use.

Roland.

 

[Roger Hicks]

The modern ZM C-Sonnar has enough contrast wide open that the focus shift is easily observed.

On classic Sonnars (for example my Canon 50/1.5 and two Nikkors 50/1.4) the contrast is dramatically reduced when opening up from f2 to f1.5/1.4, so it's much harder to observe. Still it's there. My Canon is optimized for middle apertures, my Nikkors for wide open use.

Also, with the LTM Sonnars, where the shift occurs obviously depends on the LTM adapter that you use.

Roland.

Dear Roland,

Exactly.

Cheers,

R.

 

[lam]

The modern ZM C-Sonnar has enough contrast wide open that the focus shift is easily observed.

On classic Sonnars (for example my Canon 50/1.5 and two Nikkors 50/1.4) the contrast is dramatically reduced when opening up from f2 to f1.5/1.4, so it's much harder to observe. Still it's there. My Canon is optimized for middle apertures, my Nikkors for wide open use.

Also, with the LTM Sonnars, where the shift occurs obviously depends on the LTM adapter that you use.

Roland.

My findings as well, when I owned a ZM C-Sonnar it was optimized for f2.8, everytime I shot at f1.5 I had to compensate. With my old Nikkor, I just let loose, cause I knew it wouldn't be that noticeable anyways.

 

[thompsonks]

Thank you so much, Donald, for the careful test. It confirms my simple idea that I can do well to shoot at f2.2 and f5.6-8.

Nice collection of periodicals!

Kirk