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

billythek wrote:

andrewD2 wrote:

billythek wrote:

andrewD2 wrote:

That's not how it shows itself, 24mm usually is no/less problem.

http://www.photoluminaire.co.uk/posted/6B9C4262.jpg

Explain to me why the center of the far middle tree is sharp and yet the base of it isn't.
Then look at how sharp the corners are of the foreground tree that were just the other side of a fence from me. No other lens I have does this, the old 24-70 actually curved the other way!

Luckily it doesn't affect my intended use, I tested for field curvature at a few meters and its minimal.

Andrew

Not sure what I'm supposed to get out of that picture, regarding field curvature. It looks to me that focus was somewhere near the railing of the fence surrounding the close tree. Is the complaint that the whole scene is not in sharp focus at f/5.6 with a full frame camera, when the focus point is set somewhere close to the camera?

To me, the tree in the middle is entirely out of focus because it is farther away from the focus point, as are everything else that are even farther away. I don't see anything that I would call "sharp focus" on that tree. There are some branches that appear to be a little less OOF that are extending towards the camera, which would put them closer to the focal plane.

If the complaint is that this lens/camera combination doesn't have much DOF at f/5.6 when focused at something nearby, well that is true, but not really a cause for complaint in my opinion. If someone wants massive DOF, they shouldn't be using a full frame camera. Thin DOF is one of the reasons to use such a camera.

Like I said, I didn't check for field curvature other than at 24mm, and saw some, but it was pretty minor. There could be worse problems at other focal lengths, but will need to do my own tests to verify, with subjects which are actually flat rather than trees which tend not to be. Also, I thought the OP's complaint occurred with focus set to infinity. Here, the focus point is far closer than infinity.

Anyway, I'm done with this, unless the OP wants to post pictures that show what he is talking about.

Look at the top right of the tree. Its centre image and in focus.

OK, I went back and took one more look, just to make sure I didn't miss something the first time.

Sorry, I still don't see it that way at all. When I open your file and view at 100%, the tree in the center of the image does NOT look focused to me, especially not the top right of it.

My theory about the picture is that it was taken in AF auto-select mode, perhaps as a result of being in the full automatic shooting A+ green box mode. The camera chose which AF points to use, and chose the ones closest to the camera that could achieve focus, which is what it is designed to do, and happened to be on the closer tree on the right, or the fence around it (but most likely the trunk of the tree).

Of course, I could be wrong about that, but if you had actually focused on the far tree in the center of the picture, it would be in much better focus. The 24-70II is not that bad at making trees sharp.

You are welcome to other opinions, though. Perhaps you can start a poll and have people vote on it. That will not change my opinion, but it might be an interesting social experiment to see what some people will say.

Green box mode? I have that? Lol.

Single focus point chosen, actually there is a bit of front focus but the centre is still sharp. I have now set +2 at 24mm and +5 and 70mm. That helps, the field curvature is still there but it's not starting as far forward in the centre.

You can get the exposure mode from the exif and the focus point from DPP.

I had plenty of live view focused 10x mag examples that showed it very well.

Well, whatever the cause, if you were trying to focus on the far tree in the center of the frame, you didn't do it. The 24-70II is able to get much sharper images than that in the center. If you have other pictures which actually show the point you are trying to make, please show them.
--
- Bill