Got a great deal on a Zeiss C Sonnar ... struggling with focus shift

[mcfingon]

You're welcome. We did have a good Leica tech in Perth, Western Australia but he retired recently. I did the rangefinder adjust myself as I didn't have any of my lenses with me when I went to Perth to have the shutter speeds on the M6 adjusted.
John Mc

 

[CharlesDAMorgan]

May help but there is a longish post on 35mmc about the Zeiss C Sonnar. Hamish McGill asked Zeiss about the settings from factory for the lens for focus shift - in the article but the summary

"The out-of-factory adjustment of the 50mm C Sonnar when combined with a perfectly adjusted camera rangefinder will show about 1.5cm front focus at f/1.5 and 1m focusing distance, perfect focus at f/2 and 1m focusing distance, and about 2-3cm back focus at f/2.8 and 1m focusing distance."

That may or may not help!

 

[pyeh]

PFD, I am in Sydney too. You're welcome to try your lens on my M9 and digi CL if you like. It will give you an idea where the misfocusing lies.

 

[alexandru_voicu]

PunkFunkDunk, congratulations on your new purchase. I've read what the other people posted on this thread and I must say that some replies were more or less inaccurate.

I have had my C-Sonnar adjusted by Zeiss in Obekochen for what the people at Zeiss consider "the best compromise". This means that the photographer must accept a slight front focus when shooting wide open and slight back focus when closing down. How much front focus and how much back focus at minimum focus distance? About 1.5 cm when shooting wide open at the minimum focus distance (90 cm). As you close down to F2.0, the front focus roughly halves and by F2.8 the lens starts to back focus a little. In other words, the "best compromise" is a lens adjusted for perfect focus at F2.2 or F2.5.

What can you do? Put your camera on a tripod and shoot wide open a chart at minimum focus distance. Focus as carefully as you can and shoot. Without refocusing, start closing down the lens and take a photo at each individual step. Do it until you reach F4.0. Analyze the frames. The focus should move backwards with each individual shot. When the target is in perfect focus, that is your workable aperture. In my case, as I mentioned, is F2.2 or F2.5 (can't really remember my result). You will use this aperture as the "safe aperture". If you close down, you'll have to slightly compensate to bring the focus slightly closer and vice-versa.

Most of the spherical lenses with no floating elements do focus shift. Even the Planar 50/2 does it it little. The Biogon 35/2 a little more. But the C-Sonnar is the worst offender. However, it can be tamed.

If you don't like "the best compromise", you can have your lens adjusted for shooting wide open, but you can say goodbye from shooting closed down, as the manual compensation will have to be a lot larger - and therefore impractical.

Alex

 

[colker]

Forgot to add that my incentive to figure out the C Sonnar use is that in my M system hiatus last year I shot mostly a F2AS with Zeiss 50/1.4 ZF.2 but found the Planar renderings vanilla. Nothing wrong, but nothing magical, unless the light made it so anyway. Which is true of all lenses of course but the C Sonnar makes even pedestrian assemblages or still life objects sing. And the portraits of course.

As I say this I just recalled my short stint with the CV 50/3.5 Heliar that I fooled around with back when I had my M2 three years ago. Amazing optics but horrible ergonomics for casual shooting. Still regret selling it however. I do not wish to repeat that seller remorse with the C Sonnar through my own temperamental impatience. To be continued. Somehow I always bleed money with the bloody M system.

Now you are talking. First thing i would find a tech around you.. And calibrate everything.

 

[Richard G]

PunkFunkDunk, congratulations on your new purchase. I've read what the other people posted on this thread and I must say that some replies were more or less inaccurate.

I have had my C-Sonnar adjusted by Zeiss in Obekochen for what the people at Zeiss consider "the best compromise". This means that the photographer must accept a slight front focus when shooting wide open and slight back focus when closing down. How much front focus and how much back focus at minimum focus distance? About 1.5 cm when shooting wide open at the minimum focus distance (90 cm). As you close down to F2.0, the front focus roughly halves and by F2.8 the lens starts to back focus a little. In other words, the "best compromise" is a lens adjusted for perfect focus at F2.2 or F2.5.

Alex

I agree with Alex. His figures here are almost exactly what I found in my tests, https://www.photo.net/discuss/threa...c-sonnar-apparently-optimized-for-1-5.461113/ with my lens optimised for around f2.4. M Fogiel found that a truly 1.5 optimised lens is almost unusable at f2.8 and f4 because of the back focus. He has another optimised for 2.8.

Focus shift is unavoidable and you just have to learn to live with it. Close in it is better not to use f1.5 if you can help it, if you need critical focus. Or bracket the focus. Or just take several shots. Standing with a camera to your eye you may have at least 1cm body sway anyway.

 

[jawarden]

Forgot to add that my incentive to figure out the C Sonnar use is that in my M system hiatus last year I shot mostly a F2AS with Zeiss 50/1.4 ZF.2 but found the Planar renderings vanilla. Nothing wrong, but nothing magical, unless the light made it so anyway. Which is true of all lenses of course but the C Sonnar makes even pedestrian assemblages or still life objects sing. And the portraits of course.

As I say this I just recalled my short stint with the CV 50/3.5 Heliar that I fooled around with back when I had my M2 three years ago. Amazing optics but horrible ergonomics for casual shooting. Still regret selling it however. I do not wish to repeat that seller remorse with the C Sonnar through my own temperamental impatience. To be continued. Somehow I always bleed money with the bloody M system.

Agree. No need for seller's remorse here - you got a special lens for a good price that you can resell if it doesn't work for you. You stand to lose nothing by calibrating everything and working with it for a while. That way if you eventually sell it you'll be selling a lens you've analyzed thoroughly instead of just punting it prematurely.

 

[willie_901]

This!!!

This!!!

Tip: slavishly following the RF is not helpful on any Sonnar. To hit focus below f/2.8, you will turn the focusing ring to the left by a hair (toward infinity). It will be the smallest perceptible motion you can make with the focusing ring (as in you just feel it move).

Your only other option is to recollimate the lens for f/1.5, which will royally screw up your focus at f/2-2.8-4 (and possibly 5.6) unless you are committed to hiking the focus in the other direction. I think it's better to work with it set at 2.8; this is the same way every single fast lens is anyway (the 75/1.4 is exactly the same thing) - they all front-focus at wide apertures.

And in terms of affect, front-focus is almost always preferable to back focus.

I have used pretty much every version of the Sonnar that you can jam on a Leica, and they all behave pretty much identically. Sonnars are also far easier to learn on a digital body, since you can instantly see what your focusing technique is doing.

D

12345678910

 

[Ko.Fe.]

It is still possible to test this kit without additional lens,
With ground glass or its alternative.
If it is rangefinder or lens shift then distance mark on the lens and matching distance between target and ground glass should give sharp image on the ground glass,
If not, then something is wrong with the lens.
Is here any wobble, loose parts on the back?

Here is Nokton 50 1.5 asph. No focus shift issues and very pleasing rendering.
I had Planar and many J-8. I didn't find significant difference in rendering between them.
J-3 is diffrent. Planar should be sharp out of the box. Most J-8 has to be shimmied.
Most easy to shim are black ones. They also gives more contrast.

 

[robbeiflex]

I have been through all of this as well, twice. I did a lot of testing and in my case I did not find any defective equipment, but I did learn the behaviour of my lens on different cameras. The C-Sonnar is a really fantastic lens, one of my favourites, but I might not feel that way if I did not know that mine is optimal at f1.5 on film, and f2.2 on digital, and in time learn how to compensate for that. What an amazing lens though!

Before you spend big bucks, spend another roll of film on a common sense but controlled test. Here is what worked for me:
1.) Camera on a tripod
2.) Place camera at close focus to a bookshelf at an angle
3.) Focus - and remember (or better write down) the book spine you focus on
4.) Run through the apertures at equivalent exposures
5.) Place the camera/tripod at 2m (but consistent angel) from the bookshelf - repeat
6.) Repeat the above with another lens that you know doesn't have issue
7.) Develop film, print/scan/whatever
8.) Analyse the results

Consider the time and few dollars you spend to do this test as the price of confidence in whatever you do next. If you want to be even more scientific, feel free to measure the distances and angles, have fun with pythagorus, etc., but in my case I as soon as I saw the the prints / scans / jpgs I had a very good feeling for what I was dealing with.

Cheers,
Rob

 

[kxl]

I have one that’s optimized for f1.5, which is how I use it most of the time. I eeven go to the extent of using an ND filter so I can still shoot at f1.5 if it’s too bright. So the focus shift is a non-issue for me. For other uses, e.g., at f2.8 to f5.6, I switch to my Planar.

 

[Carey M]

I just couldn't live with the focus shift and sold the C-Sonnar. The size is great and the look at is really nice for people shots, but I'm sticking with the Planar.

And maybe getting a vintage Sonnar type lens for those urges...

 

[Richard G]

I have been through all of this as well, twice. I did a lot of testing and in my case I did not find any defective equipment, but I did learn the behaviour of my lens on different cameras. The C-Sonnar is a really fantastic lens, one of my favourites, but I might not feel that way if I did not know that mine is optimal at f1.5 on film, and f2.2 on digital, and in time learn how to compensate for that. What an amazing lens though!

Before you spend big bucks, spend another roll of film on a common sense but controlled test. Here is what worked for me:
1.) Camera on a tripod
2.) Place camera at close focus to a bookshelf at an angle
3.) Focus - and remember (or better write down) the book spine you focus on
4.) Run through the apertures at equivalent exposures
5.) Place the camera/tripod at 2m (but consistent angel) from the bookshelf - repeat
6.) Repeat the above with another lens that you know doesn't have issue
7.) Develop film, print/scan/whatever
8.) Analyse the results

Consider the time and few dollars you spend to do this test as the price of confidence in whatever you do next. If you want to be even more scientific, feel free to measure the distances and angles, have fun with pythagorus, etc., but in my case I as soon as I saw the the prints / scans / jpgs I had a very good feeling for what I was dealing with.

Cheers,
Rob

I agree with this as a good cheap next test. The tripod is essential because of body sway. Hand held you can never work out focus shift reliably. The child on the beach shot of yours almost couldn’t be due to the lens unless every shot you take is as bad. I will say that focussing a Leica in portrait mode is very difficult and prone to gross errors.

 

[PhotoGog]

Got a great deal on a Zeiss C Sonnar ... struggling with focus shift

PFD, I am in Sydney too. You're welcome to try your lens on my M9 and digi CL if you like. It will give you an idea where the misfocusing lies.

This is a very kind offer! My plan is to carry out some testing of the lens across apertures with a tripod to see if I can deduce where my copy is best calibrated. As I do not own any digital bodies on which to adapt it, this is somewhat tedious to do on film. If I am unable to come to any consistent conclusion then I would absolutely love to take you up on this offer! Of course, would happily shout you a lunch at a cafe for the privilege! Great generosity here on RFF ...

 

[PhotoGog]

Thank you to everyone who responded with useful advice. This portrait of my son is the best frame on three rolls of Ektar that I first shot with the C Sonnar. Yes, a touch soft at the point of intended focus, but still magical character and 3D rendering of a kind I have never experienced with lenses in 35mm systems (I can only achieve this look with my Pentax 67 105/2.4). So I will persevere. Got in touch with Youxin to book my CLA to ensure my M6 RF alignment is OK and as previously mentioned my patch flares badly so will invest in the MP finder upgrade while I am at it. More outlay of $$$ but hopefully it will pay for itself in satisfaction over the years if I can tame the C Sonnar.

 

[PhotoGog]

Got a great deal on a Zeiss C Sonnar ... struggling with focus shift

Last night I was scanning some frames shot with my Zeiss 50/1.4 ZF.2 on a F2AS (both sold to fund the C Sonnar) and the difference in rendering is palpable despite the Nikon mount Zeiss being no slouch.

 

[pyeh]

PFD, definitely a good idea to get your M6 checked over. PM me anytime if you want to use my digicams for testing. Much more convenient than film. You can also compare your ZM 50/1.5 with mine. Mine behaves exactly as described by Alexandra Voicu above.

 

[colker]

Thank you to everyone who responded with useful advice. This portrait of my son is the best frame on three rolls of Ektar that I first shot with the C Sonnar. Yes, a touch soft at the point of intended focus, but still magical character and 3D rendering of a kind I have never experienced with lenses in 35mm systems (I can only achieve this look with my Pentax 67 105/2.4). So I will persevere. Got in touch with Youxin to book my CLA to ensure my M6 RF alignment is OK and as previously mentioned my patch flares badly so will invest in the MP finder upgrade while I am at it. More outlay of $$$ but hopefully it will pay for itself in satisfaction over the years if I can tame the C Sonnar.

No pain no gain. You like the lens. Now tame the beast.

 

[ptpdprinter]

Q: My lens doesn't focus properly. What should I do?
A. Get a lens that focuses properly. All the character, magical rendering, pop, and wow factor won't make up for an out of focus image.

 

[willie_901]

Q: My lens doesn't focus properly. What should I do?
A. Get a lens that focuses properly. All the character, magical rendering, pop, and wow factor won't make up for an out of focus image.

There is another option.