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

Benedict Slotte wrote:

I suspect you are right and I rather doubt Canon did design this lens with landscape photographers primarily in mind. I know that the original brief for the original 24-70/2.8L and its 28-70/2.8 predecessor was to produce a fast zoom for photojournalist use and I doubt that brief has changed significantly with the MkII. As such some field curvature at infinity would probably be considered a reasonable trade off against other performance characteristics that a photojournalist might consider more important.

Yes, that's what I start to think as well. However, the major increase of field curvature when focusing at infinity was a surprise.

I'm certainly not implying this is the case with you but I fear some photographers do buy lenses because they are the fastest or most expensive, rather than with a realistic assessment of what they are actually going to use the lens for, and so can end up making expensive mistakes, perhaps like this. It would be nice if a manufacturer could list all the things a lens is not so good at but naive and unrealistic to expect that of course. In the meantime we rely on test reviews and hope the reviewer is able to cover the aspect we are particularly interested in.

I upgraded partly because of the much more convenient size of this lens. The design of the old one was a bit annoying in comparison. Also, the sharpness seen in reviews was just as important as a factor, but resolution tests shot at a few metres obviously say *even less* about curvature at infinity than I would have expected. Note to self: next time, test before buying at genuine infinity rather than e.g. 10 m.

Yet another technical hypothesis I made was the following: since phase detection AF relies on light passing close to the edges of the lens, chromatic aberration will supposedly make AF ambiguous, meaning that the AF system can front-focus or rear-focus depending on the colour of the subject. A lens having less CA (read: 24-70 II compared to the original) should, technically, also have more consistent and accurate AF. I noticed this also with the 24 f/1.4 II vs the original version. Less CA, more consistent AF.

More consistent AF in itself can be reason enough to upgrade. I wasn't happy with the inconsistency of the original 24-70. I don't care about CA otherwise, since it is easily processed away in Lightroom, but I do suppose it matters for AF consistency.

Name one Canon lens prime or zoom that doesn't have some field curvature (at least below 200mm where my experience lies). The very famous Zeiss 21mm has that gullwing pattern but folks manage to use it for landscapes anyway.

I shoot "from the ledge" so to speak for a lot for my landscapes meaning.... well...a pic is worth a bunch of words. See link below. I use this scene/location constantly for testing lenses and cameras and have posted it many times here on DPR. Every corner of this scene is at infinity (at least 75 ft away) for at least the first half of the focal length thus creating a "flat wall".

http://farm6.staticflickr.com/5471/9383518701_0ac494525f.jpg

I find the premise of this thread ridiculous since you are suggesting that  the 24-70 II is unusable for landscape. I use f2.8 -f5.6 for this type of scene all of the time with barely any unusable softness in the corners which I can ovberlook. If you require perfection, a tiny bit of cropping around the edges will get the job done. In fact, f8 will begin show the visible signs of encroahing diffraction and is not necessary for this type of scene.

Having said all of this, I had to return my first copy because it was decentered.