ZM C Sonnar Re-calibrated

[sjgslack]

Hi All,

I recently sent my ZM Sonnar off to Germany to be re-calibrated to f1.5. It returned back today (after less than 2 weeks), even though i haven't even received an invoice to pay yet!

But apart from the fantastic service:

The focusing at f1.5-f2 is now spot on. At f2.8 and f4 there is a bit of focus shift, but it's so nearly covered by the DOF that if i didn't know about it already i might have missed it.

Anyway - it feels like a completely new lens! I just though I'd stick this up here for anyone contemplating getting the work done - well worth it in my opinion. 🙂

Silas

 

[Ronald M]

Surprised they are still making them wrong. What good is a fast lens with focus shift full open .

 

[Mark C]

I agree, and it seems an odd approach. Leitz did it too back in the Summarit days. I honestly don't think much of anybody even knew about these issues back then.

Some people find it a non-issue, and some are not bothered by the slight adjustment. I personally can cope with a slight adjustment, but not remembering which way to go when the direction of the error shifts at 2.8. I probably would have bought one of these by now, but can not really find an answer to what to expect as far as focus calibration out of the box.

 

[redisburning]

Surprised they are still making them wrong. What good is a fast lens with focus shift full open .

it's not wrong.

and the good is when you have a lens that is unusually good at the optimized aperture for a specific situation that Zeiss considers to be more relevant than shooting wide open.

I mean personally I shoot my f1.2 lenses at f2.0 and f2.8 way more frequently than f1.2. I'd do the same if I had a c-sonnar. Very few fast lenses have good OoF rendering wide open, personally I don't think the c-sonnar is an exception. Conversely, they tend to be REALLY good at f2.0 (the best example of this IMO is the Rokkor 58/1.2) so there's that.

 

[sjgslack]

I can certainly see why they ordinarily calibrate for f2.8. It's much simpler to deal with the problem if you only have to adjust progressively from one end. Also, as redisburning says, one more commonly uses f2.8.

But for me, I also have a 50 summicron, which is the better lens in my opinion. I found that I way only using the sonnar for the extra stop in low light, hence the recalibration.

What has surprised me however is how minor the issue is at smaller apertures. The shift is worst between f2.8 and f4, but even there it's within the margin of my own focusing errors 🙂

So of course it may not be the best answer for everyone, but I'd have it calibrated wide open even as an all-day lens (and I wasn't expecting to be of that opinion)

Silas