To answer your question, I do notice an improvement in the D200 over the D70. The D200 seems faster to me. However, it's not a night-and-day sort of change for AF speed. I have no way of measuring this for sure, mind you. The D200 certainly feels more responsive, as if it's locked on with more resolve. I know that's a rather subjective assessment. You'll just have to try it out yourself, either in the store or once you've purchased the D200.
As a D70 owner, I was definitely not disappointed moving to the D200--it's an impressive piece of equipment.
As soon as I get my D200 in, I will post a response. I have owned a 2 d70 bodies and have been rather disappointed at the lack of AF response in both of them. This was one of the major factors for me to upgrade. I don't know how many times I have missed a critical shot due to AF hunting in low light. Point to note, I have a 17-55mm that improved the situation a bit, but when it comes down to nuts and bolts, spot on performance is the only answer I & my customers want.
Does anyone else out there have any experience with this combo - D70/D200 & 17-55mm f/2.8?
Just did a highly unscientific comparison in a dimly lighted 6m x 8m room - twilight with windows facing east and many areas in deep shadow. The on body focus assist light was enabled in both cases and the requested 17-55 2.8 lens used. In all instances the D200 acquired the subject more quickly, in some cases substantially so, and was also able to lock focus on lightly colored low contrast objects that the D70 failed on. Interestingly both cameras were equally successful with locking on darkly colored objects eg stained timber carvings but the D200 was appreciably faster. In doing the comparison I was surprised that persistence beyond my normal limit in allowing the D70 to continue focus attempts resulted in many unexpected successes.
>Just did a highly unscientific comparison in a dimly lighted 6m x 8m room
I think you nailed it on the head. It's the low-light situations where I noticed more of a difference, too. The D70 seemed to hunt too much.
>In doing the comparison I was surprised that persistence beyond >my normal limit in allowing the D70 to continue focus >attempts resulted in many unexpected successes.
Yes, indeed! Looking back, it seems I was much more patient with the D70 than I thought. Sometimes with the D70 AF, I caught myself thinking, "OK, how about now? No, well, how about now? Ah, come on, lock on, darn it!"
I have both cameras, my prime lens is the Tamron AF28-75, f2.8, and it appears to me that the D200 focuses noticeably faster. It was almost to the point of me thinking that the lens wasn't working, but the pictures were sharp at all of the right places. I am not sorry that I got the D200; so far it's all I could ask for.
thanks to all the posts so far, excellent answers, practical usage is better than a scientific test in a lot of cases. As in lens tests, no one ever goes out and shoots test charts. Beleive it or not my charge card was frozen (due to a phishing scam that tried to access it thru internet use) the day my local camera store called with my D200 in stock and they obviously woulndt hold it until the mess got straigtened out.
My observations with non-AF-S lenses lead me to conclude that AF sesnitivity is better by leaps and bounds than the N80/D100/D70. It is very quick and decisive. However, I do not notice a big improvement in the actual physical speed of a non-AF-S lens with the D200 motor vs the CAM900. Focusing from near to infinity with my 80-200 2.8 is about the same with the N80 and D200.