Upload & Sell: Off
I'll try to answer before the moderator shoots this post down (as he's done with my previous gear related post as this is a no-no on this forum...):
I had 2 D3s's that I replaced with a pair of D4's. To answer your questions:
1) I personally don't see any improvement in the AF in the D4 over the D3s, I was actually disappointed in the results I got with all the hype around the D4 improved AF. Where I have the most problems (not applicable for weddings) is when I have a subject fast moving toward me and I shoot a high frame rate (10fps). The keeper rate is abysmal, to a point where now I shoot 3 frames, wait a bit for the AF to catch up, shoot another 3 frames, etc... No improvement compared to my D3s's there!
I've been messing around with the settings recently and I am getting a little better results, but nothing to write home about honestly.
2) DR? Nor sure what you mean there...
3) I really appreciate the extra pixels, which let me crop a little tighter and maybe save some shots that would have been lost on a D3s. Is that a big advantage? For us sport shooters where you might be stuck in a game were all the action happens that particular day at the other end of the field, that can really if not save the day, make it a little less disastrous! But you'll definitively need to have the lenses to go with it (i.e. all pro level lenses).
Other things to consider when looking at the D4 vs the D3s:
- Improved ergonomics: when you are going to shoot 1000's of frames per day, this will make a difference. This is still not perfect (i.e. the positioning of some of the buttons aren't exactly the same in landscape vs portrait orientation), but it is better than on the D3s.
- XQD card - Honestly it's a pain. There is very limited supply and prices are really expensive when compared to CF cards. You can decide to shoot on the CF cards and get some big fat ones... but then you loose the backup... and neither Sony nor Nikon offer a dual mode reader (so you have to carry two different readers now!
- Low light / high ISO performance: it is hard to compare because of the difference in resolution, but my impression is that at equal noise level, the D4 will allow you to crop tighter because of the increased pixel count.
- Battery life: I personally don't see any difference. I have yet to run out of battery on an event on either the D3s or D4... But the fact that the batteries and chargers are different where a pain for a while when I used both cameras!
- Connectivity: if you do some studio work and want to shoot tethered, the D4 has a huge advantage there... The Ethernet and built in web server on the D4 are great. Too bad that ounce per ouce Nikon WiFi dongle for the D4 is more expensive than gold! Even as a sport photographer I would have some uses for it.
- Face recognition: This might be something useful for wedding / group shooting. I am not sure how it works exactly, but in Live View mode, the D4 is able to find faces in the frame and focus specifically on these (and might even in P mode be able to select focus distance / ISO / Shutter speed / Aperture to try to get them all in focus. Never tried tho!
Hope this helps.