p.1 #1 · 24-70/2.8L II field curvature (is this normal?)
So, once again, after getting home from a 15-day road trip I'm finally getting a chance to take a critical look at images from several new lenses and bodies. As one would expect from the title of this thread, I'm seeing massive field curvature from the 24-70/2.8LII, especially in the middle of the zoom range, even at 5.6.
An example is provided below; I went through the image from one side to the other at 1:2 and put a mark where the plane of focus seemed to be. 100% crops showing different areas of the image follow.
I owned the Mark I version of this lens and never noticed such extreme curvature, and it was, in fact, my go-to lens for group portraits (which I also need this lens to be). As you can see from the plane of focus, I'm not sure how anyone could get any sort of group portrait without lining them up along said 'line in the sand'. And for what it's worth, some landscapes at 24mm and focused out towards infinity exhibited soft left and right sides as well (f/5.0), similarly alarming for me given how most contend that this lens is sharp from corner to corner. In other words, I'm thinking that this lens just can't be 'right'.
Has anyone else seen such pronounced field curvature from this lens? It's going back for a replacement, but I'm wondering how likely I am to get the same thing back, as some of this is almost certainly lens design, to some degree.
p.1 #2 · 24-70/2.8L II field curvature (is this normal?)
That's pretty fierce. I may get motivated and try shooting a sequence at f/2.8 with mine. Probably need to check 2-3 focal lengths for comparison.
I don't think this is a repair issue so long as the lens behaves properly with the newspaper on the wall test. But I'd check that first to see if the corners are equally unsharp just in case a lens element is out of alignment.
p.1 #3 · 24-70/2.8L II field curvature (is this normal?)
In a recent post, we saw that most lenses have some field curvature. My 11-24 and 17TSE have it and even at landscape apertures it can cause issues. I focus my 17 and 11-24 on an edge and at f11 or f13 to get good edges at some cost to best central sharpness.
I have not seen this with the 24-70 f2.8 mk2 but I seldom shoot below f8.
Your pattern is weird. I almost always have very sharp lower center (where the R is) and softer corners and edges. At f5.6 everything in the pattern ought to be sharp. I am not sure where you focused from reading your post.
p.1 #4 · 24-70/2.8L II field curvature (is this normal?)
ben egbert wrote:
Your pattern is weird. I almost always have very sharp lower center (where the R is) and softer corners and edges. At f5.6 everything in the pattern ought to be sharp. I am not sure where you focused from reading your post.
Good point; I probably focused around the furthest tip of the heart or just beyond, just below where the center 'mark' is located.
p.1 #5 · 24-70/2.8L II field curvature (is this normal?)
This is exactly what I see with mine. I think it's part of the lens design and why I only use it for certain types of images. This is just part of knowing your equipment and working around its limitations.
p.1 #6 · 24-70/2.8L II field curvature (is this normal?)
Peter Figen wrote:
This is exactly what I see with mine. I think it's part of the lens design and why I only use it for certain types of images. This is just part of knowing your equipment and working around its limitations.
If that's true, then I probably need to break up with this new girl before the relationship goes any further.
With this sort of characteristic, how could anyone possibly get a group portrait in acceptable focus, short of lining people up along the 'line'? Shooting f/5.6 vs. f/8 wouldn't make *that* much difference in this shot, and some group portraits have to be staged in a straight line.
So, in trying to evaluate whether this lens can be useful for me, here is the effect upon a typical landscape. North Rim of the Grand Canyon, horribly crappy monsoon weather, horribly crappy handheld image. The center of the image is what I would consider to be acceptably sharp given the shooting conditions, but the left and right side of the image in no way resemble the center. Does your lens also exhibit this phenomenon? At f/2.8 I might be able to stomach 50% of this lack of sharpness, at the edges (now we're back to the Mark I lens), but shooting at f/8 shouldn't add *that* much to the effective sharpness nor DOF, in this case of near-infinity focusing (i.e. 1/4 mile or 2 miles).
Thanks for providing any clarity on what's considered normal and acceptable for this lens.
p.1 #7 · 24-70/2.8L II field curvature (is this normal?)
The middle of the range, here at 42mm, is probably where the lens is at its weakest. I recently did a group band photo on location shot at 24mm and f/11 and it was very very nice everywhere, but the both ends of the focal range are where this lens is best. I have seen exactly what you're showing at 50mm in a landscape setting. Zoom lenses are a compromise and this is definitely where this one is compromised. It's a phenomenal lens when used closer in with people and you don't need everything in focus or the corners don't matter, which is the case in many images. Now, if you shot this with a Sigma 50mm ART, you'd be singing a very different tune.
p.1 #8 · 24-70/2.8L II field curvature (is this normal?)
Peter Figen wrote:
The middle of the range, here at 42mm, is probably where the lens is at its weakest. I recently did a group band photo on location shot at 24mm and f/11 and it was very very nice everywhere, but the both ends of the focal range are where this lens is best. I have seen exactly what you're showing at 50mm in a landscape setting. Zoom lenses are a compromise and this is definitely where this one is compromised. It's a phenomenal lens when used closer in with people and you don't need everything in focus or the corners don't matter, which is the case in many images. Now, if you shot this with a Sigma 50mm ART, you'd be singing a very different tune....Show more →
Which tune is that? (not familiar with the Art lenses been out of the Forum game for quite awhile)
Landscapes shot at 24mm and f/5.6 also exhibit this lack of sharpness away from center; would you consider that to be 'normal' for this lens? Perhaps we're dating identical twins?
I just can't imagine that these results are typical for this lens, otherwise I'd think people would be returning them in droves, after all, it's supposed to be somewhat of an all-around lens, especially for landscapes. Honestly, for all its quirks the Mark I gave me similar overall image quality, for a *much* lower price. I've not seen the center-to-corner sharpness from this lens that all the reviews were crowing about when it came out. I do see that kind of stellar performance from the 16-35/4 IS, however, and wouldn't trade it back for the 2.8 II for anything...
p.1 #9 · 24-70/2.8L II field curvature (is this normal?)
No, 24mm @5.6 should be pretty darned good. I'd first try shooting the same scene right side up then upside down and see if the pattern of unsharpness is the same. If it's not, then you have a problem with the lens. You can also try shooting a lens test target and examine it closely to look for inconsistencies, but printing a target big enough to be meaningful with a wide angle lens is beyond the scope of most of us.
p.1 #11 · 24-70/2.8L II field curvature (is this normal?)
"Which tune is that? (not familiar with the Art lenses been out of the Forum game for quite awhile)"
The Sigma 50mm 1.4 ART is, in a word, a remarkable piece of glass. It's probably the second best 50mm lens available for Canon, with the Zeiss OTUS being the best, but the Sigma has autofocus, virtually zero distortion and is sharp beyond belief even out to the very corners on a 5DS. It's also a relative bargain compared to the Zeiss at about $850 these days, down about a bill from when it was introduced. Oh, and a very flat field of focus. This lens has completely changed how I feel about 50mm lenses.
p.1 #12 · 24-70/2.8L II field curvature (is this normal?)
ben egbert wrote:
Here is one from my 24-70 at 30mm f11 focused on the distant mountain.
Thanks for that, but hard to tell anything relevant about focus plane from an 8000 pixel image reduced 90%
Any chance of providing a few small 100% crops of relevant parts of the field of focus, especially on the foreground if there are extreme deviations in the plane as the foreground departs the (near) DOF?
p.1 #13 · 24-70/2.8L II field curvature (is this normal?)
Peter Figen wrote:
"Which tune is that? (not familiar with the Art lenses been out of the Forum game for quite awhile)"
The Sigma 50mm 1.4 ART is, in a word, a remarkable piece of glass. It's probably the second best 50mm lens available for Canon, with the Zeiss OTUS being the best, but the Sigma has autofocus, virtually zero distortion and is sharp beyond belief even out to the very corners on a 5DS. It's also a relative bargain compared to the Zeiss at about $850 these days, down about a bill from when it was introduced. Oh, and a very flat field of focus. This lens has completely changed how I feel about 50mm lenses. ...Show more →
Interesting, may have to dump my EF50/1.4 (my least-used lens) and pick one up. Thanks!
p.1 #15 · 24-70/2.8L II field curvature (is this normal?)
Jeff wrote:
Thanks for that, but hard to tell anything relevant about focus plane from an 8000 pixel image reduced 90%
Any chance of providing a few small 100% crops of relevant parts of the field of focus, especially on the foreground if there are extreme deviations in the plane as the image departs the (near) DOF?
I will look for some. I generally find bottom corners and edges to be the toughest. But at 100% everything looks soft on an 88 dpi monitor. Going to lunch, check back this afternoon.
p.1 #16 · 24-70/2.8L II field curvature (is this normal?)
Jeff - It's really a bargain at the price. And it's sharp enough to use wide open when you need it, which, as you know is almost pointless on the Canon. All I can say is that it's opened up all sorts of new possibilities.
p.1 #18 · 24-70/2.8L II field curvature (is this normal?)
I have had 3 Sigma ART 50 1.4 lens and no matter how hard I tried with the dock and the camera microfocus adjust I just could not get my three to focus at all. I understand when you get a good copy they are amazing. My 7Dmk2 and 5Dmk3 were unable to even remotely get them to be in sharp focus. I spent hours trying
p.1 #19 · 24-70/2.8L II field curvature (is this normal?)
I bought perhaps the first 50 ART to hit L.A. and I did have focus issues with it. Sigma was very good about dealing with it even if it did take more time than I had hoped. It was the first one they had back and didn't even have the software from Japan yet to deal with it. That's not the case now. This is now one of my most reliable and certainly best built lenses. And while I do have the adjustment dock for it, I have not had to use it. The Sigma 35 ART also has a stellar rep.
p.1 #20 · 24-70/2.8L II field curvature (is this normal?)
100% crops for Jeff. Bare in mind this is a very dark image and I used it as a how far can you push it using Gdanmitchells workflow. I just had it on hand so I posted it. As I said, nothing looks good at 100% on a 50 mp camera. But this is what the raws look like at 100%. The focus was on the mountain. Then I am showing left center and a left corner. You be the judge.
