I tried the 1.4 II teleconverter today on my d4 withe a 200-400 vr2 and I could barley get enough light through the viewfinder to focus manually. Works fine in live view mode and on my d800. Also is taking pictures fine and AF works. Put in a fully charged battery with no change. Anyone heard of this? Am I missing a setting somewhere? Same issue with the 1.7.
Welcome to Nikonians! With a maximum aperture of f/5.6 with the TC-14E II I would expect the viewfider to be darker than without the TC. What was the ambient light level? Did you have the lens fully locked in the TC and the TC fully locked in the cameras lens mount? Is the viewfinder dark with the 200-400mm w/TC-14E II mounted on your D800 in the same ambient consitions? Good Luck and Enjoy your Nikons!
I use the 200-400VR-I a lot with baseball and a 1.4x Nikon TC. I have had zero problems with it on the D4 (nor the D800). Nice bright view - not quite as bright as without, but no issues either manual or auto-focus, and quite sharp.
Can you look down your lens and see if maybe you have an electronic problem that is causing it to not stay wide open? Maybe it's not really at 5.6, but is closing down on you?
I use my d4 with the Nikon 500mm f4.0 vrII lens and tc 1.4EII and tc 1.7EII with no apparent darkening of the viewfinder. I've used the 1.7 tc on dark rainy days with the 500 lens with no problems. I prefer the use of the tc 1.4EII over the tc 1.7EII for more consistancy of sharp auto focus.