Comparative focus test of 2 versions of C Sonnars

It's good to hear real use stories. I'm definitely getting one and will trade my Summicron against it. I just think the 'Cron has too much bite to it and would appreciate the extra stop or so.

In other peoples experience, how does the focus shift issue work at distances between 3-10 or so meters? Does the actual place of focus when at f1.5 move forward proportionally? That would be my only concern, that I would be in a low light situation focusing on something at 5m and actually get a result focused 12.5" in front of the subject and the natural DOF coverage at that distance not being enough to cover the margin or error.

Actually, as I write I'm checking the Online DoF calculator and at that distance there is some overlap in DoF to nearly cover focus shift as the DoF at f1.5 would be 0.85m and the focus shift would be about 30cm forward. This reminds me of Roger Hick's article and what the dude at Zeiss told him about the DoF coverage. Easy to get around, IMO.

Either way, I'm going to get one. I just think the images I see made with them have the look I'm missing since migrating to modern lenses. Can't wait to get my hands on one!
 
TJV said:
how does the focus shift issue work at distances between 3-10 or so meters? Does the actual place of focus when at f1.5 move forward proportionally? That would be my only concern, that I would be in a low light situation focusing on something at 5m and actually get a result focused 12.5" in front of the subject and the natural DOF coverage at that distance not being enough to cover the margin or error.
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Have not noticed any, I always assumed that any focus shift was eaten up by DoF.

Hope you enjoy it, it's a great lens!
 
After almost a year with the C Sonnar optimized for f/2.8, I am contemplating, with some regret, having Cosina adjust it for f/1.5 .
Overall, I still think the lens is best optimized at f/2.8 . However, since I usually carry this lens in a kit with other lenses that are slower, I end up turning to the C Sonnar precisely for its speed. And most often at MFD. Here the focus shift is pronounced. I have been trying to train myself to compensate. However, although my success rate has increased with practice, the results are still not reliable enough for me.

I'll probably regret the change in performance at f/2.8 - 4.0 once the lens is recalibrated by Cosina, but
everything is a compromise.
 
It's great that the option to have the lens recalibrated is there, and for free! I can't imagine Leica ever offering such a service for free. It's interesting to note that the Noctilux shifts more in focus according to most tests I've seen.

I'm really looking forward to getting my Sonnar. I have to thank a friend who I met at work who will send one back for me from Singapore. I'm stressing what sort of film to run through it first, colour or BW!

noimmunity said:
After almost a year with the C Sonnar optimized for f/2.8, I am contemplating, with some regret, having Cosina adjust it for f/1.5 .
Overall, I still think the lens is best optimized at f/2.8 . However, since I usually carry this lens in a kit with other lenses that are slower, I end up turning to the C Sonnar precisely for its speed. And most often at MFD. Here the focus shift is pronounced. I have been trying to train myself to compensate. However, although my success rate has increased with practice, the results are still not reliable enough for me.

I'll probably regret the change in performance at f/2.8 - 4.0 once the lens is recalibrated by Cosina, but
everything is a compromise.
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I've owned the ZM 50/1.5 C Sonnar optimized for f/2.8 and found it to be a good performer providing that the lens gives exactly correct rf focus with the camera body used. An easy way to tell would be to make sure the lens didn't cause the camera's rf patch to overshoot infinity coincidence at it's endpoint, even in the slightest amount. If it falls slightly short of perfect coincidence, this may be quite acceptable as well since this mitigates effective focus shift by inducing a little "backfocus" to offset the "frontfocus" effects of it's inherent focus shift.
 
Dante_Stella said:
Try this focusing technique with the Sonnar. At f/1.5, focus from near to far and stop at the farthest distance where the RF arguably lines up. At f/2 and smaller, focus the other way and stop at the nearest distance that the RF lines up. Your break point may be f/2.4 or f/2.8, but you can figure this out pretty quickly.
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I wonder if someone can help me with this one.

I'm not understanding what Dante is telling us with this focusing technique. Can anyone explain it so that I cna understand. The problem is me - not Dante - but I'm just not getting what he's saying. Help.

Thanks.
 
Huck, what Dante is saying is that it makes a difference as to whether you rotate the focus ring from nearest focus or from infinity due to play in the rangefinder mechanism on Leica Ms.

I confirmed this by marking the position of the lens focus ring when focusing on an object 3 metres away. When focussing from infinity to 3 metres the rangefinder lines up a bit further away than 3 metres on the focus scale of the lens. When focussing from nearest focus to 3 metres the rangefinder lines up a bit nearer than three metres markings on the lens.

You can use this way of focussing to make up for a bit of front or backfocus in the lens if you know its behaviour.

I hope this makes it clearer

Gert
 
T - I opted to get a lens optimized for f1.5, because: 1) I don't want to have to adjust when I want to shoot wide open, and 2) if I stop down, the DOF will "hide" the focus shift anyway. As others have said, in the real world, I'm not sure that it matters one way or another.

Example - on the street, with a subject 10 feet away: at f1.5, DOF is about 1 foot, while at f2.8 DOF is about 2 feet. A lens optimized for f2.8, even with focus shift, would still capture the point of focus within its DOF if shot wide open at f1.5. However, since things are moving relatively fast on the street, I would typically stop down anyway and shoot at f5.6, which makes moot the question of optimizing at f1.5 or f2.8.

I'll post some when I get a chance.

Keith
 
Sonnar is a very attractive choice. First here is mentioned "new" and "old" version and new was 1.5 calibrated. Was that new/old true for Zeiss manufacturing or something personal purchace? Did I know which one it is when buying brand new and Zeiss is manufacturing both still?
 
Zeiss calibrate them to f2.8 out of the factory and for special requests adjust it to f1.5 for fee under warranty.
T

mirrored said:
Sonnar is a very attractive choice. First here is mentioned "new" and "old" version and new was 1.5 calibrated. Was that new/old true for Zeiss manufacturing or something personal purchace? Did I know which one it is when buying brand new and Zeiss is manufacturing both still?
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i dont understand one thing - why zeiss dont make f2 version - i think that version would cover both mistakes on f1.5 and f2.8... i think it would make f1.5 acceptable and on the edge of DOF and also it wouldnt make big mistakes on smaller apertures...
 
kxl said:
T - I opted to get a lens optimized for f1.5, because: 1) I don't want to have to adjust when I want to shoot wide open, and 2) if I stop down, the DOF will "hide" the focus shift anyway. As others have said, in the real world, I'm not sure that it matters one way or another.

Example - on the street, with a subject 10 feet away: at f1.5, DOF is about 1 foot, while at f2.8 DOF is about 2 feet. A lens optimized for f2.8, even with focus shift, would still capture the point of focus within its DOF if shot wide open at f1.5. However, since things are moving relatively fast on the street, I would typically stop down anyway and shoot at f5.6, which makes moot the question of optimizing at f1.5 or f2.8.

I'll post some when I get a chance.

Keith
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Since the focus shift changes, it's not covered by DOF as you stop down. You just experience focus shift at different apertures. As I recall, it's f/2.8 & f/4 with the lens optimized at f/1.5. So, you have to choose your poison.
 
TJV said:
Zeiss calibrate them to f2.8 out of the factory and for special requests adjust it to f1.5 for fee under warranty.
T
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The adjustment is free under warranty. Customer pays for shipping.

Huck Finn said:
Since the focus shift changes, it's not covered by DOF as you stop down. You just experience focus shift at different apertures. As I recall, it's f/2.8 & f/4 with the lens optimized at f/1.5. So, you have to choose your poison.
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It's worth repeating, too, that the direction of the focus shift relative to the camera is different. On the f/2.8 optimized version shot at full aperture at MFD, the DOF falls well in front of the point of focus. On the f/1.5 version at f/2.8 and f/4, the DOF goes back starting from the point of focus. So with the latter, you at least have a reliable index in the VF of where the starting point of the DOF lies.

A word about focusing technique: for the f/2.8 version, it is often said that all you need to do is "focus on the ear" at MFD and full aperture. In practice, I found this is much harder than it sounds. It may sound elemental, but ears are not actually all that visible. Trying to focus on an ear in its natural habitat, i.e., covered in hair, especially in low light, is much harder. Noses and eyes, generally exposed, offer excellent targets for low light focusing.

(I did try and practice quite a bit with other techniques such as the unidirectional focus, the physical lean-in, the additional turn of the lens. But I couldn't get my results to be reliable at f/1.5 and MFD on an f/2.8 optimised lens. But that's just me. Other people will have better technique, Bravo!).
 
Huck Finn said:
Since the focus shift changes, it's not covered by DOF as you stop down. You just experience focus shift at different apertures. As I recall, it's f/2.8 & f/4 with the lens optimized at f/1.5. So, you have to choose your poison.
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Without knowing what the actual focus shift is at f/2.8 and f/4 at distances greater than the MFD, that's not possible to prove or disprove.

Example: presetting the focus to 10ft, @ f/1.5, DOF is 1 ft (9.5 ft to 10.5 ft); @ f/2.8, point of focus shifts back to 10ft + X, with DOF of 2 ft (1 ft in front and 2 ft behind); at f/4, focus shifts back to 10 + X + Y, with DOF of 3 ft (1.5 ft in front and 1.5 ft behind).

So, as long as X is less than 12 inches and X plus Y is less than 15 inches, DOF will be sufficient, the point of focus of 10 ft. will be within the DOF.
 
Huck Finn said:
Since the focus shift changes, it's not covered by DOF as you stop down. You just experience focus shift at different apertures. As I recall, it's f/2.8 & f/4 with the lens optimized at f/1.5. So, you have to choose your poison.
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Correction: I checked my notes & it is at f/5.6 that focus shift is a problem when the lens is optimized for f/1.5.

I also came across an interesting note from Dr. Hubert Nasse in a correspondence we had about the C-Sonnar. It reads as follows:

"As a rule of thumb, you may assume that up to f/5.6 the focus shift roughly corresponds to half of the total depth-of-field. In other words: in a lens in which the lens & the lens cam are adjusted for best focus at f/1.5, when the camera is focused with the rangefinder, the best focus of the stopped down lens will be at a distance which is not at the main index but at the corresponding DOF mark.

The shift is positive, so the best focus distance is larger than intended. This means that the distance at the left of the DOF mark has to be set to the main index to achieve best focus of the stopped lens. (As with all non-floating lenses , these effects get a bit stronger at close distance.)"

I hope that this is helpful.
 
after a few months of messing with the C-Sonnar, optimised for f/2.8, i am finally giving in and having it re-calibrated by Zeiss Germany (they are great to deal with, btw).

i use this lens, more often than not, wide open on my R-D1 (which i believe, is less forgiving than a film camera). i shoot in very low light most of the time as the 75mm-equivalent (1.5 crop factor) makes the 50mm lens less than ideal for street.

i love the lens but have agree with noimmunity that focusing on the ears is easier said than done.... having to "lean in" also messes with your framing and i've just become altogether to obsessed with getting focus, making the lens less of a joy than it should be.

TJV asked for a real world example. here's one taken at minimum focusing distance and then leaning in (larger version here):
 

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also, i need to make a CD of images to show Zeiss where the focus shift occurs on my camera (they have an Epson, but says each camera is unique).

does anybody have suggestions on the best way to go about this?

thank you in advance!
 
Hi cam. I sent my C Sonnar to Cosina yesterday.
If that's the way you are going about it I would just send the camera body with the lens. Especially since it is just over the Rhine, the turnaround should be very quick and no extra import duty.
 
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