(This post is from an email conversation with a coworker. I thought the content might be useful for others.)
Q: Are you shooting everything at the full 36.2 Mp or have you played with DX crop. Im thinking with the DX crop you still get 15.3 Mp (more than the D3 or D700) and you get that effective 1.5x from the crop.
A: Definitely using the DX crop often. I have a button assigned to give me the option so I press that and rotate the dial between DX and FX (easily, w/o removing my eye from the viewfinder). The screen shows a box around the DX image area when DX is selected.
That ability to switch easily and minimize the file size where appropriate is one of the big positives for me. It has been available in the D700, etc., before, but only now does the resolution make it a viable option. (Well, I guess it would have been OK with the D3X, but that’s a bit pricey.) The D800 can be a souped up D700 for normal shooting, but also instantly become a replacement for the D300 (w/better resolution and noise) for birding, etc.
The sample image of the Warbler was in FX mode only because the thing was too close to get in the frame of the DX crop, so I quickly switched to FX and fit her in perfectly. BTW, that’s a real improvement over the D300 for me. And shooting in DX mode, you have the area around the crop indicator to help you know what’s just outside the frame and what may be on its way into the frame. It’s a little like having the 200-400 zoom. I can see a larger area to help with quick framing, and I can zoom out if need be by switching to FX. (I remember shooting whales with you wishing I had your zoom’s flexibility to help quickly acquire the subject and then get tighter once I had it in the VF. This gives me something close to that, at least to help get the subject in the VF more quickly.)
And the 15+MP is definitely a step up from the D300, both in resolution and quality of pixels.
I’m really concerned about the storage thing getting out of hand, so the DX option really helps there when I’m birding.