Originally posted by osv you could be right about the dof, if i wasn't perfectly parallel to the side of the car...
... i was already at iso10,000, and i dropped the shutter to maybe 1/2000th(?), and even tried to pan on some of the shots, to make up for the slower shutter.
I could be wrong here, but it seems to me that EVEN IF you had been perfectly parallel to the car, even then, the straight-line distance from your lens to the car's middle is different than the straight line distance from your lens to the car's front fender/rear fender (simple triangular geometry).
Depending how far you were standing from the subject, this difference in distance I suspect may be enough to cause the fender portions to be slightly out of focus with respect to the car centre, simply because of the somewhat inadequate DOF at f2.8.
Put another way, the centre of the car may well be in accurate focus, (which it is in that picture), but the front and rear ends of the car, being quite a large subject, may already be drifting slightly out of focus, all the more if you were standing quite close by snapping the shot. And I think the only way out is to stop down more, maybe f4 or 5, to increase DOF. But I know this causes ISO noise.....
Also, even with some other lens, which is sharper in the corners when wide open, it still can't solve this problem, because sharpness can't overcome out of focus; hence the need to stop down to obtain enough DOF, and as a bonus, also get improved corner sharpness.
This was one of the points I was making earlier - when a lens is wide open or near wide open, the DOF is going to be small, and it's going to be really, really hard to get any significantly large portion of the picture to be in focus, no matter how sharp or not sharp the lens may be, because the DOF is shallow. So sharpness in the corners wide open just isn't relevant in most cases I can think of, because the DOF is going to be so shallow.
Wow, didn't realise it was 1/2000 second. I'm not experienced capturing motion at such high shutter speeds. Was 1/2000 needed? Because for sure that would run your ISO way up.
Love the fill flash in the second shot...