In addition, you really shouldn't be pixel peeping a lens, especially a wide angle lens with a CPL on. CPL's can cause strange results with wide angle lenses. Have you tried the same test without the CPL? I wouldn't be surprised if the results are much better.
"Finally, as I regard this as being within normal lens performance boundaries for a 24mm lens when viewed at 100%"
Respectfully disagree. It might be normal for a zoom, but not a good prime.
A 24L Mk2 is expensive but at f11 its images are stunningly sharp on a 5D2, even at the corners. even at 100%.
Although i've no experience of the Canon TS-E 24mm f/3.5 L II, that has the reputation of being a really great lens too.
I recommend you start saving for one of these 2 lenses. Wide angle zooms are fine up to a point, but its clear to me that in your heart of hearts you don't like to compromise! I have the 24L prime for critical work, and the excellent 24-105 when I need flexibility.
I think f/16 would have solved it. Furthermore I think you are demanding a bit much from a budget L zoom like another poster mentioned. Unless you are printing something large does it really matter?
gdanmitchell wrote:
There are lots of things that can cause corner softness, but in the second example a couple slots before this comment there is little to no specific evidence of field curvature being the issue. To show that you would need a sample in which the level of optimum focus stayed the same but the distance from the camera to the optimally focused subjects was different. The second example cannot show that, given the closely spaced comparison points and the fact that the degradation is more associated with position in the frame than anything else.
I do not understand how you can say that the sample above isn't indicative of field curvature. When the focus distance is at infinity, the bottom center is sharp but the bottom corners are very soft. You say that this degradation is associated with position in the frame. And yet look at what happens when the focus is moved from infinity to 2m. Now the corners are almost as sharp as the bottom. The only reason it appeared "soft" was because it was out of focus.
If degradation was associated with position in the frame, then the corners would be soft regardless of focus distance... wouldn't it?
gdanmitchell wrote:
Your original example does not demonstrate it either, at least not convincingly, since all elements in the defocused area are somewhat out of focus.
It may not have looked convincing because I separated the affected areas by cropping them. I will present the same areas together without the crop. Look at the photo below and remember that my focus distance is in the foreground (not infinity).
The sharpness of the foreground foliage is reasonably even. The sharpness of the background terrain is very clearly not even. To me, it looks like the right background terrain is in focus, but the left background terrain is out of focus. That's why I concluded it's an example of field curvature.
On the other hand, if the softness was simply due to position within the frame, then the foreground sharpness would've been just as uneven as the background.
(Also: This not a "decentering" problem because remember the entire crop above is from the left side of the full frame. I assure you that the foreground on the other side of the full frame is very much in focus)
crazeazn wrote:
I think f/16 would have solved it.
I agree. Having shot with APS-C for so many years, I've become accustomed to the idea that f/11 is sufficient for maximizing depth of field with my EF-S 10-22mm lens. That habit has carried over to 17-40L on full frame. I probably should be using f/16 more often than I do.
crazeazn wrote:
Furthermore I think you are demanding a bit much from a budget L zoom like another poster mentioned.
I don't remember "demanding" anything at all. I was only trying to learn more about the idiosyncrasies I noticed with my lens. I did not realize some people would chastise me for my curiosity just because the lens in question was a "budget" zoom.
crazeazn wrote:
Unless you are printing something large does it really matter?
Well, it satisfied my curiosity about the oddities I was seeing. And it convinced me to use f/16 more often. So yes, it matters.
I had the same experience with the 24-85...sideways "stretched" grass on the left side but NOT the right side...I got rid of that lens...the 28-105/3.5-4.5 does not exhibit this phenomenon..
