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

Benedict Slotte wrote:

I have tried a few copies of this lens, and settled on the one that was best among them. In spite of this, I do see significant field curvature in landscape shots (read: focused close to infinity) even at f/8, meaning that not even at f/8 will it be possible to have decent sharpness from one edge to the other.

And that's a pity, because I think at least one review said it was better than version I in this respect. I'm not sure what focusing distance they were referring to there, though.

As pointed out, curvature is not something that is usually adjustable, it's part of the design.

This might be an interesting read:

http://www.lensrentals.com/blog/2013/09/there-is-no-perfect-lens

Question to all owners of this lens: what are your own copies like when focused at something distant? I'm starting to think that this lens is just not designed for use with landscapes at all, but rather optimized for shooting at closer distances.

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

andrewD2 wrote:

I praised the lens at 24mm and at all focal length and there is far far less CA than the old 24-70II at all focal lengths. I sold my old one and I like the new one. Mostly due to the lighter weight. Because you feel I'm knocking your expensive baby doesn't make real issues go away. Equipment is a business, not personal, thing for me.

I've got plenty of gear to compare it to and its the only lens I've noticed strong field curvature on.

At 40mm and f2.8 the pancake is sharper across a scene that is parallel to the sensor and focused in the centre.

Do the test yourself.

The most expensive choice is not always the best landscape lens. E.g. the 85/1.2 huge front element makes it a poor choice.

Andrew

You are arguing that the 24-70's field curvature is strong (obviously a matter of opinion and taste) but for the sake of argument and those avid readers of Photozone, I'll stipulate to that. What I am saying or should have made clearer is that this lens' field curvature doesn't harm most scenics. If you are shooting the horizon at water level, maybe you'd want less field curvature. If you have mixed scenics with buildings and straight lines in your composition, the smart lens is the TSE-24mm but you lose the bennies of the 24-70 II.
But the OP wants "decent" edge sharpness across the frame and I am telling you, he ain't going to find it as he presumably defines it if he has such a low opinion of the 24-70 II @f8.

But, let's see the visual evidence. I don't mind standing corrected.

Rick Knepper wrote:

But the OP wants "decent" edge sharpness across the frame and I am telling you, he ain't going to find it as he presumably defines it if he has such a low opinion of the 24-70 II @f8.

None of the overly dramatic wistleblowers here want to answer a simple question: at what aperture the field curvature is within the DOF? Let us assume the curvature is there wide open, but at f/8 the DOF is from 10 yards to infinity. Is the field curved from infinity all the way back to 10 yards? Doubtful.

Secondly, a lot of landscape folks successfully use 17-40 that is not the sharpest blade at the edges. Does the field curvature of 24-70 II stopped down make it softer than 17-40? I'd find it hard to believe.

Unless these questions are answered, this is much ado about nothing.

This one comes closer to proving your point, although I'd rather see test shots of something that was truly flat (in a plane) and farther off, if the complaint is about the curvature of the infinity focal plane (and not just the thinness of the DOF, or soft edges in general). Not saying the problem doesn't exist. Just it would be good to truly isolate field curvature from other effects.

What I'm thinking of is taking a picture of a row of objects off in the distance that are known to be in the same plane, and you are shooting perpendicular to that plane. Shoot one shot where the center is in optimum focus, and presumably the edges will be out of focus due to the curvature. Then manually adjust focus so that the edges are sharp and the center is out of focus. How much you can turn the focus ring to make that adjustment is a measure of how much the focal plane is curved.  If you can't make that adjustment, and the edges never get sharp, then you are seeing some other problem, like soft edges in general.

You also have to separate field curvature from the fact that the DOF is surprisingly thin with a full-frame camera if you are pixel-peeping, even at moderately long distances.  So if the objects you are taking a picture of are not in the same plane to begin with, you have to wonder if it is field curvature, or just the fact that they are nearer or farther than the focal plane.

You guys will have to carry on without me. I'll be in Yosemite this weekend. Maybe I can find something flat there to do some tests on.