Zeiss Sonnar 50/1.5 M Mount Question

[whitecat]

I have more than one Zeiss lens and was about to look into the 50mm. I do remember reading that this lens had a problem with focus shift and at a certain aperture it was slightly out of focus. Any truth to this?
Thanks

 

[EdwardKaraa]

Yes, the c-Sonnar has substantial focus shift and beautiful rendering. If you like the rendering, you need to learn how to deal with focus shift. Some samples are calibrated for wide open, while others are calibrated for f/2.8. It is difficult to get information from the online stores about that.

My copy was calibrated for WO. Here is what to expect:


1.5 by edward karaa, on Flickr


2.0 by edward karaa, on Flickr


2.8 by edward karaa, on Flickr


4.0 by edward karaa, on Flickr


8.0 by edward karaa, on Flickr

 

[whitecat]

Thanks for that info. Amazing how such a fine prime lens can have this "problem". I might go to the 2.0.

 

[Monochrom]

Hi it is in deed.

But the out of focus area depends on which optimization it´s made in the factory.

Optimization @ 1.5 menas:

1.5 in focus, but from 2.8 on you´ll have back focus, so if you want to shoot sharp at 5.6 you wonñt make it.

2.8 optimization menas you´ll have perfect focus from 2.8 till the end, but you´ll miss focus at wider apertures than 2.8 about 1, 5 inches front focus.

In the past all of the sonnar were optimized at 2.8 because it´s the steadier way. And if you shoot a 2.8 optimized lens at 10 feet you´ll have perfect focus...but noone does such a thing...

Bye!

 

[EdwardKaraa]

Thanks for that info. Amazing how such a fine prime lens can have this "problem". I might go to the 2.0.

You're welcome! To be honest, I really loved the rendering of the Sonnar but I wasn't too keen on the focus shift (which affects many RF lenses by the way, not only the Sonnar). I think the 50/2 Planar is a more universal performer, while the Sonnar is a specialty lens that will give you amazing background blur and three dimensionality. I kept the Planar and sold the Sonnar, but if I took more portraits and low light shots I would have done the opposite.

 

[Benjamin Marks]

Mine is "optimized" for 2.8 and it really is an amazing lens. But it is not a lens you can turn your brain off when you use. If you have a camera like a NEX that lets you focus through the lens stopped down, you can do away with the focus shift without too much effort. If not, or if you are more of a "fire and forget" kind of guy, the Planar is also a great lens - easily the equal of the Summicron in sharpness, if not quite in build quality.

BTW, many, many lenses have a bit of focus shift inherent in their designs. Often it is masked by depth-of-focus as you stop down. This particular 50 Sonnar design has enough that you have to learn the lens a bit to get the best out of it. No biggie, and less in fact than it used to be, as you can get instant feedback from the digital cameras that will take this lens.

Ben

 

[whitecat]

I got this off of the Popflash Photo site......


-all production since 1997 is focus optimized at f/1.5 for film based cameras to a FFD distance at 27.86mm.

-this adjustment works well for film based cameras, but causes a noticeable shift on digital rangefinder cameras - since their FFD is longer than film-based M-mount cameras (basically they do not meet the standard M-mount spec). When the optimized lenses are tested with digital rangefinder cameras at a close focus distance of 0.9m and at f/1.5, they front focus by about 2cm

-because of the differences between film and digital rangefinder cameras - which we cannot control - it is impossible to have a focus optimized C Sonnar for both systems.

-for customers who want their lens adjusted for digital rangefinder cameras, Zeiss Germany have set the FFD to a distance of 27.90. This provides good results on digital cameras, but will cause a focus shift on film cameras for the reasons mentioned above

-If an individual customer wishes to have their C Sonnar optimized for use with a digital camera, the customer can send the lens into Zeiss Germany for adjustment.

 

[Richard G]

My Sonnar was apparently optimized for 1.5. I have rarely observed focus shift in practice. Mine seems to be optimized for about f2.4. Here's the test:
http://photo.net/leica-rangefinders-forum/00aKSW

 

[mfogiel]

Take a look here:

http://www.rangefinderforum.com/forums/showthread.php?t=51742&highlight=TWO+VERSIONS+OF+C+SONNAR

This is the best 50mm potrait lens ever made, but you have to know what you want from it. Personally, I prefer it at f2.8-4.0. Wide open it becomes a bit exaggerated, with low contrast, bokeh as if it was a 0.7 lens and some bleed from the highlights. On digital, this looks slightly more aceptable.

 

[whitecat]

I had a 50mm Summilux and did not have to play the little adjustment senario. I guess I am going to do a little research into the Contax 2.0.

 

[Steve Bellayr]

The problem occurs wide open at the minimum focus distance. I shoot wide open. For example at 20 feet there is not problem.

 

[EdwardKaraa]

The focus shift is caused by under corrected spherical aberrations. The 50 lux is well corrected.

 

[thompsonks]

In practice it's less a problem than it might seem.

1) You can check your own lens and use it accordingly. IMO you have to do this anyway, because besides the different factory optimizations, you'll find sample variations and lens/body mating variations. With a ruler test like the one above, mine turned out to be optimized for closest distance at f2.2. So I shoot at that aperture, or else at f5.6, with no problems.

2) As mentioned above: the smaller the aperture and the farther away, the less you can see focus shift anyway – it's compensated by DOF. But f 5.6 is as far as I like to stop down, because at smaller apertures the lens becomes quite contrasty, losing the 'classic' character that was the reason for buying it in the first place.

BTW, 50 pre-aspherical Summiluxes do exhibit some focus shift. Did you mean aspherical?