Hi to all,
Just thought I would share my opinion on the D4 and D800. It might help some of you guys out.
I owned a D3s and D300 and now use the D4 and D800 for weddings, model shoots and urban photography.
First I would like to state that the D4 is just the best camera I ever owned. It is really superb. I also shot with Canon (5D mkII) but the Nikon models just feel better when holding them. When it comes to overall image quality I would just as easily use a Canon camera. Just to point out I am not one of those guys who loves to bash the other brand :) Nikon or Canon are both great camera manufactures but I just prefer Nikon.
On all camera's I use a 14-24 2.8, 24-70 2.8 and 70-200 2.8. So there was no difference regarding lenses.
The picture quality of the D800 and D4 are in my opinion pretty much the same. The higher resolution of the D800 makes reducing noise somewhat easier and brings out a little more detail.
The D4 however is much better build. I find the D800 more plastic and it feels somewhat cheap.
But when it comes to model shoots the higher resolution is just great to have.
During a wedding I use the D4 for the make-up shots, ceremony, diner and party. But for the bridal shoot I use the D800 for 90% off the time. When I need higher ISO's I drop the D800 and go back to my D4.
The D4 is fast while focussing and has a better ISO performance than the D3s. Most say that the ISO performance of the D3s and D4 are the same but that is not true. I can go up to ISO 10000 on my D4 and get the same quality as when I shot at ISO 6400 on my D3s. For my D800 and Canon 5D MKII I won't go higher than ISO 3200. And on my D300 I really didn't go any higher than ISO 1200. Just to point out that I am really picky when it comes to noise.
The battery life of the D4 is also better than some say. I shoot around 1700 images during a wedding (starting at 8:00 AM till 1:00 AM) and still have 3 bars left.
I don't do video so I can't say if Canon does a better job on this part.
In my opinion the D4 is the best camera to have.
If you can afford it, go for it. I sold my D3s and paid a lot extra for the D4 and find the better focus (in the dark), higher resolution (for cropping) and better ISO performance are worth the money. For all types of photography in which you need a fast focussing monster camera this would be the one.
When doing solely model shoots or urban photography the D800 would be the best choice because of the higher resolution.
For nature photography go for the D800E.
If you don't need the higher resolution and don't have the cash for a D4, then buy a second hand D3s. You can buy one for around 3000 euro's which is the same price as a D800. But the D3s is much better build. And the ISO performance of a D3s is so much better than on a D800.
Hope this will help some of you decide.
You can find my work on pixed.nl