50 C Sonnar re-calibration

[sjgslack]

So,

I have just taken the plunge and sent my C Sonnar to Germany to be re-calibrated to focus correctly at f1.5.

Since getting a 50 Summicron I'm finding I don't use the Zeiss much - having it set to f1.5 will make it my go-to indoor lens to use almost exclusively wide open.

My question is - has anyone else done this? And if so, what's your experience? (especially regarding how accurate it is and how much focus shift there is at smaller apertures).

Silas

 

[Richard G]

No I haven't done this. Mine seems to be optimized for about ƒ2.2. It slightly front focuses (1cm) at ƒ1.5 at 1m, and then slightly back focuses at ƒ2.8 and ƒ4, where the depth of field cancels out the effect of the focus shift. mfogiel of RFF had a ƒ1.5 optimized copy that was unuseable at those other apertures mentioned above, so he has an ƒ2.8 optimized copy as well. maggieo of RFF seems to have a C Sonnar optimized like mine.

 

[sjgslack]

Maybe the answer is to have one in between like yours 🙂

I'm envisaging only really using mine wide open now as i like the rendering of the Summicron more at smaller apertures... It will be interesting to see how it is!

Silas

No I haven't done this. Mine seems to be optimized for about ƒ2.2. It slightly front focuses (1cm) at ƒ1.5 at 1m, and then slightly back focuses at ƒ2.8 and ƒ4, where the depth of field cancels out the effect of the focus shift. mfogiel of RFF had a ƒ1.5 optimized copy that was unuseable at those other apertures mentioned above, so he has an ƒ2.8 optimized copy as well. maggieo of RFF seems to have a C Sonnar optimized like mine.

 

[brbo]

I had my C-Sonnar optimized for wide-open at Zeiss in Oberkochen. It came back with still a slight front focus @1.5. I guess they aim for something like f1.8 or f2 when you send it to them for wide open optimization.

 

[sjgslack]

Thanks for the info. That sounds pretty reasonable

I had my C-Sonnar optimized for wide-open at Zeiss in Oberkochen. It came back with still a slight front focus @1.5. I guess they aim for something like f1.8 or f2 when you send it to them for wide open optimization.

 

[jonmanjiro]

I had my C-Sonnar optimized for wide-open at Zeiss in Oberkochen. It came back with still a slight front focus @1.5. I guess they aim for something like f1.8 or f2 when you send it to them for wide open optimization.

Same as Cosina in Japan. I've sent several Sonnars to them for optimization to f/1.5, and they came back calibrated like your lens. I spoke to an engineer about it on the phone, and he said if a lens was calibrated to focus perfectly at f/1.5 it would be unusable at more moderate apertures.