I am an "early adopter" of a D4 - due to the generosity of a friend who got his order in before I did, but decided not to keep it himself. It's a GREAT tool, but one which has already spent some weeks back at Nikon already. The first failure was of all circuits that handle external inputs. It was fixed and updated, under warranty, of course.
Yesterday I turned it on and took a couple of test shots before an event that I was shooting. I was surprised to see gross underexposure. I played around for a few minutes but without finding any obvious reason for the underexposure. It bahaved similarly with my 24-70 f/2.8 and with my 14-24 f/2.8, so I put it back in the car and used the D800 instead. I had a bunch of shots to take indoors without flash - a situation for which the D4 is ideally suited! Anyway, I shot at ISO 2000 with the D800 and am fairly pleased with the results.
Back to the D4: This morning, I investigated the problem fairly thoroughly but found no explanation. Auto exposure (I use Matrix mode 99% of the time I'm using auto) is low by, typically, 2-3 stops. However, if I turn on LV, the exposure is accurate. Using full manual and setting exposure according to my Sekonic meter, yields perfectly exposed shots.
Can anyone offer a suggestion? I have already tried complete resets, but to no avail. No settings seem to be "wrong".
I'm beginning to think that this body needs to go to El Segundo AGAIN.
EDITED to add that, when in full manual mode with shutter speed and aperture set according to the Sekonic meter, the camera's exposure indicator shows significant overexposure - but the actual shot is correctly exposed. This seems to confirm that the camera's exposure system has taken a turn for the worse!