In another topic there was a lot of generalized discussion of Focal, to the extent useful here is one for a specific lens/camera combination if anyone else cares to try.
I did this test with the standard target at the left, center and right focus point, at 14mm and then at 24mm, at about 2.4m distance. Then I ran one more at a distant (30m) target.
These look concerning as it would appear I have inadequate adjustment capability to actually get the best focus. Most of these curves are still rising as they approach the left (-20) axis, and would seem to imply that I need a greater negative value than -20 to get the best look. In all cases except the 14mm/center Focal gave a -20 recommendation, and there it was -13 but a quite flat curve (i.e. -17 was close to the same value, though -20 was down quite a bit).
Focal, interestingly, hung in an infinite loop 4 times trying to do the right focus point at 24mm.
I've had quite good real world results with the 14-24 (adjusted to -18). So I am not too worried, but this makes me think my D800 really does have a focus issue, perhaps even at the center, to need such strongly negative adjustment. Or maybe it is the lens.
Does anyone have similar results from a D800/14-24/2.8 combination?
I'd be careful with focus adjustments on wide lenses. It may be your lens - or camera - but you have so much DOF to work with that an AF adjustment is usually unnecessary.
Testing on the ultrawides has been inconsistent on all bodies - its very hard to truly tell if AF is off due to field curvature, huge DOF, and the very wide field of view. Focal is a good tool, but I would look for more consistent results as short to medium distances. DOF is near huge at 30 meters so I would not use that test.
Congrats on your new camera. It really is spectacular.
Sun 29-Jul-12 11:09 AM | edited Sun 29-Jul-12 11:12 AM by Ferguson
>Yes - that's a huge improvement. That's a big enough >difference that service might be in order.
These are 1:1 crops on a very dense sensor, so for the wide angles you would need an awfully large print, or a pretty tight crop. But still...
I am coming to the conclusion that the D800 needs to go back first. It clearly has some left side issues, and at the very least those adjustments will probably make all this change in some way, then see if any lens has issues.
That's disappointing, as frankly I was happy with the focus on all lenses except the 85/1.4. I had largely convinced myself I did not have the issue, or at least not enough to fix. But bad real results drove me to do the testing, now naturally I see even more problems. Sigh.
A reason one who is fully happy may want to avoid testing.
Same thing happened to me-I complained from day one that I could not get a sharp image w/the camera - just thought it was a learning curve on the new babe until I did the test-Obvious as ever in images & tests just confirmed!
I get mine back this week so the sooner you send it in the better!
Art is the only way to run away without leaving home.
I believe the 14-24 has focus breathing issues at 2.8. That being said, I don't completely understand the concept, so perhaps it doesn't apply to your situation.
If you can get your D800 adjusted easily, you may wish to do so. But if it's a hassle, I might ask how often you shoot your 14-24 with autofocus, especially on one side. For situations that demand that wide an angle, I am almost always using live-view manual focus. OTOH, I completely understand if the idea of a defective $3000 camera bothers you; I think mine is in the clear.