>Thank you very much for the info. If I might ask a couple >other comparison questions, since I haven't found anyone yet >who has used both.
There are a few of us out there.
>Given my primary paid photography genre is horse events >(rodeos, cutting horse shows, etc.), how would you compare the >two for AF tracking of fast moving subjects?
Fast moving, means different things to different people, and conditions can mean a lot too. Tracking a VERY fast moving object in good light and with good contrast is very easy for nearly any camera. Tracking a somewhat fast moving object in poor light, and with horrible contrast is a test for all AF systems. I tend to break down AF performance in 2 primary ways.
1. Arc distance. Or how far across our 180 degree field of view the camera must move to track a subject. Imagine yourself on an oval track with cars going around. If you stand at the very center, the cars will be moving relatively slowly but in a very wide arc. If you stand close to the track but at the end of a straight, the cars will be moving in a VERY simple way from the far end of the previous turn, but as they get closer, they will be harder to focus on.
2. Dwell time. This one really is about how long an AF system needs to lock focus on a moving subject. If the subject is still, dwell time is short. If the object is moving rapidly, the AF system needs longer to verify distance to target and compute in what way that target is moving so it can begin to track. The D3s/D4 are excellent at this. The D800 also quite good but slightly less so. The D600 will be better than your current camera, but not up to the standard of the pro level cameras.
>Surprisingly, this just occurred to me...I have learned I can >get what I need 80% of the time with 1 shot or 6fps, it does >no good if the camera cannot track the subject well, >especially in less than ideal light ( think covered arena lit >with sodium lights, using strobes for the actual image)
This doesn't really tell me much. I shot tennis this week in a venue where the correct exposure was 1/500, F2.8, ISO 3200. How does that compare to your environment?
>I know the area covered with the AF points is smaller in the >D600. Can you comment on how the AF area size difference >affects your photography, if at all? What about the 9 v 15 >cross-point sensor difference?
None at all. And frankly, I didn't even notice it until someone pointed it out on the internet. I use the center point or the 4 surrounding it on every camera I own.
>Thanks in advance for any additional input you MIT be able to >offer.
I saw later on you are shooting with an 80-200. An upgrade to the 70-200 will make a bigger difference in your focusing speed than putting that 80-200 lens on a D4. In my opinion anyway. I still have my 80-200 but it's a backup now.