Sonnar 50mm 1.5 - optimized at which F stop?

[jc48375]

I recently aquired a nice Sonnar ZM 50mm f/1.5 - the seller didn't know if it was optimized at f/1.5 or f/2.8.

It has worked flawlessly on my Fuji X-T1 -

I am about to buy a Zeiss Ikon ZM body and would love someone to help me identify how this lens is optimized..

Besides running a test on the camera body when it arrives, is there anyway I can tell how it was optimized with the serial number?


cheers,

 

[mfogiel]

No, serial numbers are unlikely to help, but most of these lenses were optimized for f 2.8, or actually 3.2, where at portait distance they deliver a stunning combination of sharp plane of focus with nicely melty background and a strong 3d effect. Wide open on film, this lens is rather low contrast and weaker resolution, so it is better to shoot it this way on some sharp emulsion, or on digital.

 

[Robert Lai]

Mine is about 2-3 years old, and it seems to be optimized for f/2.
For wide open I need to nudge inwards 1-2 cm. At f/2.8, the depth of field seems to cover the intended plane of focus.

 

[willie_901]

After a while one Zeiss offered free f 2.8 lens optimized for early units. I think the only way to know is test it on an optical rangefinder camera

This optimization was only to alter the focus shift behavior (not eliminate it). I don't remember any discussions of rendering differences.

I don't see how the focus shift modification is relevant for adapted lens usage on a camera with an EVF. In fact I don't think it's relevant with the X-Pro 1's OVF.

 

[Monochrom]

Thre is a simple test to know the optimization of the c_sonnar.

Put a ruler in a table then shoot at a given distance at 1.5 and then at 2.8.

Once you develop and scan you´ll know.

The best optimization for the c-sonnar is 2.8, the lens will pin focus from 2.8 to 16. and at 2 and f1.5 it will front focus at short range...but at 3 meters it will nail focus again.

The 1.5 setting is mediocre, beacuse from 2.8 up to 16 the lens will back focus by meters! Some say it´s ok becuase at 16 the dof will compensate...

So get it optimized at 2.8 that is the correct setting.

 

[mfogiel]

The solution to focus shift is simple: buy two C Sonnars... Cheaper than one Summilux...

 

[Michael Markey]

Great lens ... love mine .
My copy is optimised at 1.5.

 

[:: Mark]

Mine was bought new this year, and is set for exact focus at f2.8 (on a rather more ancient M7). I find that don't need to compensate for focus shift if shooting f2 or narrower.

The infinity stop seems also to be set at f2.8, which means that it is not possible to perfectly focus at infinity with the lens wide open on the M7.

With an adapter on u4/3 it is very easy to see the focus shift, and the adapter I have seems to allow focus slight past infinity. Aside from testing, it was quite helpful as a means to practice how to compensate when shooting wide open.

And yes, this is a great lens...

 

[Richard G]

Doing your own tests is the best way, if you seriously want to tread this dangerous path. It's harder than you think. You need a tripod, that's for sure. And a ruler, and something which you can focus on precisely. And Lightroom is a great help with the resulting images zooming in to 2:1 to look at the focus. I tried this on film with some chess pieces and a note book and it was a mess.

Mine is optimized for about f2.2 I think. This give slight front focus by a cm at 1.5 at 1m and slight back focus at 2.8 and 4 which is quite liveable.

There are users who've happily shot the lens and had no problems and have never heard of focus shift. It's too late for you, however.

 

[Doug]

Personally, I shoot f/2 and wider very little of the time, so f/2.8 optimization is my preference. For wider apertures it's easy to just lean forward a little after focusing to get it right. But if you shoot wide open a lot, that's another matter.

 

[Roger Hicks]

See about a third of the way down http://www.rogerandfrances.com/subscription/ps firstlook sonnar 50.html for a real-life test of focus shift (+ review).

Cheers,

R.