Upload & Sell: Off
if you read the comments following the pictures in the link, you'll find that some one states you can set the d700 to have masking also:
I didnít realize that turning the AF Point Illumination off (Menu item A6) would also enable the masking. Thanks ovas. Iím sure that means the D800 will do that too.
Read more on NikonRumors.com: http://nikonrumors.com/2012/02/11/nikon-at-the-2012-cp-show-pictures-d800-hands-on-d4-demo-videos.aspx/#ixzz1m7VMnv1D
I don't have a d700 anymore, so I can't test it out, but someone should clarify this info
I have a D700 and yes, this is the way it works. With A6 'OFF' and image ares set to DX the viewfinder is masked like the D3.