Consensus on 24-70/2.8 II field curvature at infinity focus?

Benedict, thanks for binging this up. I'm in a similar situation as you are. I always do buy several samples of a zoom lense and pick the best. I have seen great sample variation with tamron (as expected). With the Nikkor 80-200 2.8 there was non at all ( 3 samples), and the Nikkor 18-35 2.8 had extensive variation also. As i'm just switching platform, i have no experience with canon (actually i have, but thats 20 years back). Can you desribe how the samples differ and did you test several focal lengths or just one? I expect corner resolution to vary mostly, right?

All lenses (well, I don't know about Zeiss, perhaps they are in a league of their own?) have some asymmetry. Most commonly, the focal plane is tilted in some way. It's almost never perfect (which is understandable). Also, it can be almost perfect at one focal length and tilted at another. No matter what brand is in question.

I care about this if it's obvious enough to be distracting. The first copy of the 24-70 II that I tried actually had a very severe left/right tilt at 24 mm but none at all at 70 mm. It was enough for me to shoot 4-5 photos to see it immediately.

To my best knowledge field curvature is not really subjected to sample variation (lense alignment), but is a design limitation.

The only thing you can do about it is to harmonically optimize diffraction and hyperfocal distance.

Yes, I think field curvature is less dependent on unit variation - but not completely, since I suppose any extra offsets in the distances between elements can alter field curvature as well.

B. Slotte
Turku, Finland
http://bslotte.smugmug.com