Lance B
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Jay968 wrote:
I think that one of the things I have seen with the 14-24s is that its field curvature very often makes it look as if the corners are not very good. I've tested it against a flat surface and found that it is indeed very sharp corner to corner. But in real world shooting field curvature does some nasty stuff to foreground corners. It's imperative to either get to know how this behaves and work with it, or stop down enough to try and avoid it.
The Photographylife review of the lens which you have provided the link to seems to contradict this.
I'm not exactly sure why, but if I photograph a flat surface, I see very little falloff in sharpness in the corners. However, if I photograph a landscape I see corners ranging from what I would call fair wide open to acceptable at F8 and pretty good at F11, but still discernible from the center of the frame. I'm not sure what those who say the corner sharpness on this lens is superb are looking at or shooting. There is always a noticeable difference in sharpness between the bottom center and bottom corners. If this is not due to field curvature, I don't know what accounts for it. No I don't expect any ultra wide to have perfect corners, but the praise I have seen for corners on this lens is something I just don't understand. I've done some decentering testing using Fred Miranda's technique and while not perfect (what ultra wide zoom is) I see no problematic evidence of decentering.
I don't know Photographylife but I do sometimes wonder if some reviews are based on published MTF curves and not on real hands on use. The MTF curves for the 14-24s are superb. Far better than what I am actually seeing in using the lens.
Most samples that I see from this lens (including your terrific images at Nikon Cafe) seem to be of landscapes which have either dark or non detailed foregrounds. I've been searching for examples which show a lot of detail in the near foreground areas, but they are few and far between. In another forum I asked anyone who owns this lens to take a few simple shots of something beyond 20 feet or so but also showing the foreground closer to the camera. I have yet to see a shot which shows real good edge to edge sharpness in that foreground unless shot at at least F8. However, as I said earlier, a brick wall test makes the lens look superb corner to corner.
If not field curvature, then what is accounting for this?...Show more →
Thank you for your kind comments on my images at Nikon Cafe.
I have been advised that the published MTF charts fom Nikon are calculated, not measured. I do not know how you are judging these MTF's and what you are "seeing" in the results as not being indicitave of it's performance. As far as I can tell, the MTF charts reflect the lens's performance quite well as do the resultant test results from Photography life and elsewhere. This is a super sharp lens and indicated by the test results at Photography Life and yes Photography Life actually tests the lenses on a test bench. They also use the lenses in the field.
Field curvature should not be an issue if you are focusing in the correct plane fror the lens. This is why it is important to get to know your lens. If we consider DOF - at 14mm and f5.6 and focusing at 2mts (6ft), DOF runs from 740mm (3ft) to infinity! At 24mm f5.6 and focusing at 3.5mts, DOF runs from 1.73mts to infinity. In other words, if you are standing to take an image, pretty much everything will be in focus from your feet to infinity at f5.6. Use f8 and it will be even better.
If the 14-24 f2.8S is considered a fairly flat field curvature lens, then focusing nearer to the front of the image should give you sharpness edge to edge and well to infinity. So, if you have focused at these distances and the field curvature is reasonably flat as like a test chart, then you would have good sharpness into the corners and edges. If you are focusing deep into the scene, then you may expect that the edges to not be quite as sharp if the lens has low field curvature. If it has high field curvature, then it may be better to focus deeper into the scene and then the edges will some into better focus.
I don't as a rule, "test" lenses. I take photos and judge for myself the results using my seat of the pants judgement and years of using lenses and knowing what to expect. I leave the real testing to the experts. The issue is that unless the test is controlled and repeatable, then it is not a real test and may put the lens in a good or bad light depending on how the test was done. I just take photos in real world environments, conditions, and use and judge the results against what I know and feel. As stated above, getting the focus perfectly right for the field curvature of the lens is critical for critical work and testing, whereas my real world shots are not critically focused to get full perfect DOF. However, I have a pretty good idea where abouts it needs to be for a given lens for it to be excellent in most situations, IMO.
You can see my 14-24 f2.8S images on my Pbase photo hosting site in my 14-24 f2.8S gallery here:
https://pbase.com/lance_b/1424_f28s
There are a few that have detail near the edges of the frame say like these? These are focused more to the front of the frame rather than the rear as I know the 14-24 f2.8S has a relatively flat field.
The detail in the wood to the right is there, clear and sharp:
As is the sandstone pillar on the right
The paving at my feet are pferfectly sharp edge to edge corner to corner. I mean, how good does it have to be??
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