The WT-4A (which I have) reportedly will work with the D800. I use it with my D3 in my small studio to send images to my laptop for real-time client review. I never send the raw image as that takes too long. I shoot Raw + small jpeg and send the jepg only. That goes quickly. I suspect that even with the WT-5's higher data rate it would take a long time to transfer D800 Raw files.