Comparative focus test of 2 versions of C Sonnars

Thanks for a very helpful post. I recently took delivery on the f/1.5 optimized C Sonnar for use on my Hexar RF. I think the body's very slight front focus tendency (due to extra 0.04 mm film channel depth) offsets the slight back focus (WRT the subject) resulting in a small amount of front focus wide open but at f/2.8 and smaller, it's spot on using the same focus test chart as in your examples or even a distant subject at infinity. I'll post some examples in a day or so.
 
mfogiel said:
Having thought a little bit about the results of this test myself, I've actually decided to keep both lenses... However, if anyone from Zeiss will stumble on this thread, I'd like to suggest, to make a new version of the C Sonnar - with an adjustable switch between the F1.5-f2.0 range and the f 2,8-f16 range. I think this is perfectly doable with little extra engineering. This way, you could switch the best focus position as a function of your aperture, just like you adjust a FLE in one of the Hasselblad Distagons as a function of distance.
Click to expand...

Mazurka said:
Then it wouldn't be a Sonnar design anymore -- I don't believe the classic construction can incorporate a floating element.
Click to expand...
It may not take a floating element to accomplish... It might be feasible to just have the focusing cam move slightly as the aperture is changed.
 
Hi all. This is my first posting on this forum.
I just came back from Hanoi where I spent a week shooting at night a lot, with an "f2.8 version" C Sonnar mostly at around F1.5. When the focus was "on", and that was a measly 25-30% of the time, the results were magical. But what about the '0%+ shots I had to throw away. This was with an Epson R-D1s by the way. I put the lens on sale in Tokyo and bought a highly dependable ZM Planar.
I already miss the extraordinary, heartbreakingly beautiful bokeh though...
One question: can anyone tell me succinctly how a pre-asph Summilux 50 compares with the Sonnar in terms of both "bokeh" and "focusing accuracy"?
Thanks!
 
I agree, the focus is always spot on and the bokeh is also very nice. However, the Pre-asph. Summilux does suffer from a bit more residual astigmatism outside the central image zone requiring about f/5.6 and smaller to snuff it out. The C Sonnar doesn't have this issue and this gives it a bit of an advantage for better edge to edge sharpness at apertures of f/2.8 and smaller, something useful for critically sharp landscapes when shooting between f/2.8-5.6.
 
My adventure with the C-Sonnar Part II

My adventure with the C-Sonnar Part II

Well I started missing this strange and wonderful lens like crazy so I put a STOP on the sale, called Cosina HQ in Nagano, Japan and they assured me that they would gladly recalibrate the beast at around F1.5 for free and within a week...
And that's what I've done.
Why? In Hanoi I shot wide open or at F2 in near darkness and although I managed a few luminous "keepers" I lost a good 75% of the shots. I really enjoy night shooting in SE Asia, even here in Tokyo, and in order to keep the iso at 800 or 400 on my R-D1s, there is no way around using F1.5 or thereabouts. And the bokeh wide open and at F2 is wondrous.
Hope I'm not boring everyone with this tale. Thought I'd update you on the story...
Part 3 wil be the "return of the beast" newly calibrated for F1.5...
 
I'd be very curious to see some sample images with the f/1.5 version, especially at f/1.5 and f/2.8. My concern is the possible softness between f/2.8-4 where dof may not completely cover the "new" focus shift induced at these apertures by compensating for the "old" focus shift at f/1.5.
 
Thanks a lot Mfogiel for your finding.
I have this lens with F2.8 version.I shot a lot wide open at night, and know this could be a big problem, I can move my lens forward a little or focus far a little to compensate the focus drift.

Here is my C sonnar 50/1.5 set on flickr

I felt unhappy when I knew my lens was a 2.8 version, Now I am very glad with it, I prefer the F2.8 version. the @F2.8 and @F4 is the most useful of this lens.
 
Last edited:
If it is any comfort, this is an issue that is hardly unique to the 50/1.5 Sonnar. It's present in a lot of high-speed lenses; it's just a little more obvious because the ZM Sonnar is a very, very good lens.

The 75mm Summilux can be just as tough on an M8. After you have it recollimated for a flat sensor, you can choose to (a) have the lens (or if you prefer, the rangefinder) dead-on and ultrasharp at f/1.4 and lose usable focus at f/2-5.6 to have it return at f/8 or (b) have it focus a little bit in front wide-open and either at or a tiny bit behind everywhere else.

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.

On M cameras, there is also some microscopic play in the RF system that can sometimes make a difference based on the direction in which you focus. Unidirectional focusing is explicitly discussed in the instruction leaflet for the Mamiya 6 150mm lens, so it's not anecdotal or speculation.

That said, I had my 50/1.5 recalibrated in Germany - and on the second try, it worked very well.

Dante

mfogiel said:
I've made little brackets 4cm wide, to mark the best focus zone, and put an arrow where to my eyes, the image looked sharpest.
First of all, the reference Planar shot is really quite impressive, because it really is spot on the target, i.e. the black line with the "focus here" text.

The f1.5 shots show you right away what's happening - the "new" C Sonnar looks like it's missing the precise point by 1cm, but the dof covers the best focus quite well, while the "old" version is plainly off, front focusing by about 5 cm, which is not so easy to manage in real life, making this version little usable wide open.

The f2.0 shots display a similar story, and here indeed one can see the phenomenon described by Roger Hicks and Dr Nasse - in the "new" version, the usable dof sits right behind the point of best focus. Since f2.0 is probably the most interesting aperture for low dof portraits, because it gains quite a bit of contrast with respect to wide open, yet the bokeh remains exceptional, obviously this version should perform well for the "dreamy and creamy" assignements. The "old" version is a bit like a fish out of the water here.

At f2.8 we see a capsized situation: the "new" version is disappearing behind the horizon, while the "old" starts pulling out the bite, and is entering the best overall performance zone. I suspect this lens is at it's best around f3.5, and this is where Zeiss has actually calibrated it in the first place.

At f4.0 the "new" version has become almost unuseable, while the "old" version focuses like the "new" one wide open, and, believe me, at this aperture delivers the goods in large amounts...

Finally, at f5,6 the relative best focus does not move by a detectable amount, but the dof increases, making the "new" version just useable - by f8,0 the focus stays the same and both lenses cover easily the "focus here" sign.

It is difficult to draw a definitive conclusion just on the basis of some ruler shots, and in fact I'd like to make some real portraits with both lenses, to see how it works out in practice.
However, if you are attracted to the C Sonnar for its absolute bokeh wide open, or for using it exclusively in low light and between f1.5 and f2.0, then the "new" version is for you, but you better keep another 50mm lens handy for more general shooting. On the other hand, if you like the soft but contrasty drawing with good detail, which this lens delivers between f2.8 and f4.0, plus you do not disdain great sharpnesss beyond f5.6, then the "old" version should be for you, and you might want to keep one of the older f1.4 or f1.5 lenses for the wide open soft images.
Click to expand...
 
It doesn't say, and apparently Zeiss cannot tell (or is not prepared to tell) from the serial number either, so you have to test the lens out. But you will find out pretty fast which it is.
 
noimmunity said:
It doesn't say, and apparently Zeiss cannot tell (or is not prepared to tell) from the serial number either, so you have to test the lens out. But you will find out pretty fast which it is.
Click to expand...

Exactly! You'll soon know if you test the lens.

I recently tested my Nikon S-mount Zeiss Sonnar 50/1.5 (as shown in this thread), and the results showed that its optimised for f2.8, and front focuses at f1.5 and f2. Though the front focus isn't nearly as bad as I was expecting it to be.
 
So I've revived this old thread from the ashes...

To those who are still using this lens, how about posting some shots here that prove the focus shift issue is only of very minor importance, able to be tamed, along with a note as to which version you own.

I'd love to see more examples so I can compare the Zeiss with my Summicron.
 
I had a Sonnar which I sold and didn't know which version it was. I think it was 2.8. Regardless I contacted Zeiss about adjusting it if needed, etc, and got this nice response. Thought I'd share it for those interested:

thanks for your request.
It is not possible to know about the calibration of a lens by its serial number.
Depending on the type of camera in use, the tolerances of the rangefinder and flange focal adjustment of the camera, and the preferred f-stop you are using you will get slightly different results regarding focusing accuracy.
So please make some tests with your camera to decide if you would have get the lens readjusted. Only a few photographers felt that another kind of adjustment of their C-Sonnar lens would fit better to their demands until now.

If you´d like to get your lens recalibrated, you can contact our representative in the US:

Carl Zeiss MicroImaging, Inc.
(Regional Distribution Partner)
Photo Division
One Zeiss Drive
10594 Thornwood / NY
Phone: +1 800 543 1033
rschleuning@zeiss.com
USA


or you can send your lens directly to us. Therefore, please fill out the following repair form and add it together with the neccessary documents (warranty card, copy of the invoice) to the shipment:




Here is some further information about the classic C-Sonnar lens:

C Sonnar T* 1.5/50 ZM

Information about special features for dealers and users


The C Sonnar T* 1.5/50 ZM is a very special lens; based on a classical lens design concept from the 1930´s. The additional letter “C” in the name of the lens expresses this designation.

This lens design helps to achieve pictures with a special artistic touch. This lens ‘draws’ your subject in a fine, flattering manner and is therefore ideally suited for portraiture. It renders a sharpness that is slightly rounded, being less aggressive than in contemporary lens designs, but at the same time not soft in its rendition.

Many famous portraits of glamorous and prominent people during the 1930´s used this technique to great effect. These images are characterized by portraying the person in a shining, nearly celestial way. This effect is very well balanced and not exaggerated; therefore many viewers see it in a subconscious way. The trained observer, however, understands the underlining technique and enjoys the results.

This lens design exhibits some additional effects, which should be understood to achieve the maximum benefit from the C Sonnar T* 1.5/50 ZM:

Because of the above mentioned classical characteristic of the lens the best focus position in the object space can not be kept exactly constant for all f-stop settings.
The passionate photographer might notice a slightly closer best focus in his pictures than expected. When stopping down the lens to f/2.8 or smaller this effect is minimized, so the focus position will be as expected.
In order to balance the performance at full speed and other f-stop settings the lens is adjusted with above described characteristic.

The special features of the C Sonnar T* 1.5/50 ZM are best used in emotional, artistic, narrative images, portraits or atmospheric landscapes. For documentation or technical subjects Carl Zeiss recommends to stop down the lens at least to f/5.6 or to use the Planar T* 2/50 ZM lens.

If the C Sonnar T* 1,5/50 ZM should predominantly be used at full aperture, in a few cases a recalibration of the lens to f/1.5 might be necessary to minimize focus shift at full aperture. Together with this calibration to f/1.5 comes an increase of the focus shift at f/2.8 and smaller, but this will be covered by the depth-of-field in most cases.
Because the results of the focus shift of the C Sonnar in practical use depend on different factors (e.g. on the calibration of the flange focal distance and rangefinder of the camera body in use, the preferred distances and f stops, the 3-dimensionality of the subject etc), we strongly recommend to make individual test shots with a C Sonnar before you decide to send it in for recalibration.

In most cases, a recalibration of the lens is not necessary.

If you´d like to get your lens recalibrated, you have the following alternatives:

-return it to the dealer where you purchased it, so he can send in the lens to us
-send it to our distributor in the country of purchase
-send it to us (Carl Zeiss Germany), if you have an European warranty card that came with your lens
-send it to Cosina, Japan, if a Japanese warranty card was included

The recalibration is free of charge as long as the lens is covered by warranty.



Best Regards

Bertram Hönlinger
 
Thanks Abenner.
I emailed Tony at Pop Flash to check to see if they are still coming out of the factory at f2.8 and he says they are. They will only receive ones set to f1.5 upon special request.
It's interesting because I also emailed B&H and they stated that all new ones are set to f1.5. Either way, I'd sooner trust the guys at Pop Flash.
In real world terms I doubt It'd matter anyway. My type of photography doesn't usually allow for 100% accurate focusing, it's too hurried.
 
TJV, I bought mine from Tony and it is the 2.8 version as far as I can tell. Have not noticed any focus shift so far.
 
I'm pretty much decided I'll get the lens and don't mind a 2.8 version. Actually, I think I'd prefer it set to 2.8.
It's actually hard to find decent examples of what the lens can do on the internet and seeing as there isn't anyone in NZ that stocks ZM or Zeiss lenses next to impossible to judge what it's like for myself. Think it's just time to take the plunge!
 
I'm still in the process of taming the focus shift. I have not found the proper amount of leaning necessary to be spot on.
I have Tony's 2.8 even though he/they thought it would be 1.5 optimized.
I like it better that way, and it makes for a characterful lense. I rarely use it at 1.5 and if I do, I bracket it to 2.8! Better safe than sorry!

Check flickr for images, maybe I'll post one here when I get home tonight. Not sure if it's the "Sonnar-look" (never owned a sonnar before of any kind/age), but I love the character.
 
You must log in or register to reply here.
Back
Top Bottom