Comparative focus test of 2 versions of C Sonnars

I have bought a Jupiter-3 1962 model in LTM and find it rear-focusses by 40mm at a measured 1.2 metres, when used on a test-chart with my Olympus Pen Mini and adapter. But in practice on film I am getting sharp results on my Leica IIIF and M3, so the shift is within tolerances or is less than human error. I'm very happy with the Sonnar (Jupiter?) look. It's worth the quirks.
j3_f2.jpg
 
Monochrom said:
At last the best optimization imo is the 2.8 figure, that gives you more control overall and from 10 feet on it doesn´t matter that inch of frontfocus..
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Unfortunately, it doesn't work like that. A few centimeters of frontfocus at close distance becomes a few meters at mid distance and A LOT of meters at far distance.
 
brbo said:
Unfortunately, it doesn't work like that. A few centimeters of frontfocus at close distance becomes a few meters at mid distance and A LOT of meters at far distance.
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Nop...it doesn´t front focus stays steady....it´s back focus the one varies in distances...
 
I also love C Sonnar with M8 and my way to cope with the focus shift and use this lens from wide open to smaller aperture are:

-Optimized it @ f1.5
@f1.5,f11,f16 focus as usual
@f2.0 focus a bit closer about 1/8 alignment of M8 frame line width.
@f2.8 focus a bit closer about 1/4 alignment of M8 frame line width.
@f4.0 & F5.6 focus a bit closer about 1/2 alignment of M8 frame line width.
@f8.0 focus a bit closer about 1/4 alignment of M8 frame line width.

These may not be the best way to compensate the focus shift but quite easy in practice because you can estimate the compensation comparing with the frame line width when you focus.
 
I have been debating with myself for a while to get a Sonnar, finally it arrived today. The focus shift has been a factor and many thanks for the test mfogiel has created at the beginning of the thread, just rerun it in a less professional setting: Focus is spot on and 5cm front for f/1.5, about the diameter of a espresso cup, will try that as a rule.
Now looking forward to using it
 
There has been some discussion about how they are being shipped, whether 2.8 or 1.5 optimized. Well I can say that I just bought a brand new one from B&H photo and after testing on my Ikon and on the M 240, mine is definitely 1.5 optimized straight from the factory. Focus is perfect at 1.5, and then the shift really kicks in at 2, and 2.8.

I'm loving the look but it's a tricky little lens. I plan to spend a few months with it to see if I can make it work for what I want. If I am unsatisfied by then I'll probably swap it for a 50/1.5 Nokton. But I don't want to jump the gun, so I'll be putting it through it's paces.
 
You can simply use live view when you need intermediate apertures. Actually, it would have been better the other way round: get it calibrated for f2.8 onwards, and only shoot in live view when you need max precision wide open or close to that. Anyway, this lens is just special. Something that is very close, but different, is Summilux pre ASPH.
 
Why put up with a lens with focus shift? Might be ok for slr, not RF.

If you like the portrait quality, guess how far forward you need to move.
 
Man, the focus shift from my 1.5 optimized version at other apertures is REALLY bad. It's basically unusable at f4. I had to focus a good 8 feet in front of a subject that was like 20 feet away for it to properly focus on my intended target. It's PERFECT at 1.5, but if I'm not using 1.5, I apparently need to stop down to F8. I think I will be purchasing the EVF and using it with that.
 
SaveKodak said:
Man, the focus shift from my 1.5 optimized version at other apertures is REALLY bad. It's basically unusable at f4. I had to focus a good 8 feet in front of a subject that was like 20 feet away for it to properly focus on my intended target. It's PERFECT at 1.5, but if I'm not using 1.5, I apparently need to stop down to F8. I think I will be purchasing the EVF and using it with that.
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This does not sound right in a couple of ways. First, as any contact with Zeiss will confirm, they were all made at the factory to not show focus shift at f2.8. They will front focus about one inch at f1.5 at minimum focus distance. Focus shift is inherent in the Sonnar design, and setting the lens up with this particular set of compromises to deal with it in a consistent way was just the way Zeiss chose to go. Some people in the Internet world have decided to label the lens as "optimized" for f2.8. Well, okay.
Zeiss agreed to change the function of specific lenses for people who spent a lot of time shooting wide open at one meter focus distance, by recalibrating the lens, so that there would be no focus shift at f1.5. These are the lenses which people refer to as "optimized" for f1.5. This was always an after the sale modification done by Zeiss per customer wishes.
There were never two different versions of this lens offered for sale as new, there were never old 2.8 and new 1.5 versions; that's just an Internet myth, as Zeiss has confirmed over and over.

Sample variations sure. Modified to 1.5 lenses floating around out there adding to the confusion, sure.

But, if your lens is unusable at f4 and focusing the way you say it is, there is something wrong with that copy, as they do not behave that way.
 
Maybe something changed. Who knows? I bought mine brand new less than a month ago from B&H. It's perfect at 1.5 on my my Zeiss Ikon and M 240. I have to assume that this is what optimized for 1.5 really means.
 
My C-Sonnar is clearly calibrated for exact focus at f2.8.

FWIW, this is what I got when I tested my lens at minimum focus distance. The five panels correspond from left to right to f1,5, f2, f2.8, f4 and f5.6:



I shot these while trying to understand why some of my images were very soft. However, I think that the "problem" is just that the lens itself is quite soft wide open. The shift is only an issue at minimum focus distance, but the lens is so soft at these apertures that you do not need to be very precise when compensating (eg focus on the ear rather than the eye for a close portrait). Shoot at 2m or more distance or slightly stopped down and you can completely ignore the effect.

BTW, these were shot on an M7 with Ektar 100. Does anyone know if the cover glass on digital sensors significantly affects the behaviour?
 
SaveKodak said:
Maybe something changed. Who knows? I bought mine brand new less than a month ago from B&H. It's perfect at 1.5 on my my Zeiss Ikon and M 240. I have to assume that this is what optimized for 1.5 really means.
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I don't think anything has really changed, regarding how they come from the factory, but you can confirm that with Zeiss directly. I have found them to be quite helpful and responsive, on this issue and others.

The part that raised my eyebrows about your particular sample was this:
" It's basically unusable at f4. I had to focus a good 8 feet in front of a subject that was like 20 feet away for it to properly focus on my intended target."

That's just not right, and would have nothing to do with the known and negligible problem with focus shift which is only really an issue at minimum focus distance and wide open, or close to it. There are too many good photographers using this lens who can truthfully say they have never even noticed the focus shift in routine every day use, to think that, no matter where the wide open close focus is set for, 1.5 or 2.8, that you have to focus at 12 feet in order to nail focus on something 20 feet away at f4.

That doesn't sound like anybody's idea of a Sonnar/1.5 design issue, that just sounds broken.
 
Mark, I don't think the cover glass on a digital changes anything in the centre of the lens. Off-centre with my Sony A7S there is obvious smearing. The focus-shifting behaviour of the lens is the same on digital as film from what I've seen.

:: Mark said:
My C-Sonnar is clearly calibrated for exact focus at f2.8...

BTW, these were shot on an M7 with Ektar 100. Does anyone know if the cover glass on digital sensors significantly affects the behaviour?
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brbo said:
How many f1.5 optimized Sonnars did you try?
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One, though to the extent that your question is a form of argument, which is how it seems to me, I would guess that the only answer I could give which would be satisfactorily convincing would be, "all of them."

At any rate, asking everyone else who owns a C-Sonnar 50, which has been modified ("optimized") to show no focus shift at f1.5, if it is true that the only way they can obtain focus at f4 on an object 20 feet away is to set the lens focus at 12 feet would seem to be more to the point. My guess is there will be few takers.

It isn't behavior which is inherent in the design, and isn't remotely evident in my (one, sad and lonely) example.
 
Even if you ask Zeiss for 1.5 optimization, you will get something like f1.8. But some camera/lens combos can be "real" f1.5. And yes, focus shift on a lens like this from f1.5 to f4 at 20 feet is VERY noticeable.

Argument that focus shift is present at close distances and wide open is simply wrong.
 
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