Well, Theodoros,
Pixel count of the higher sensel arrays of the D800 must be reflected in more lines/mm discerned in objective tersts such as DXOmark and Imatest. I have no doubt that you'd find that the D4 would capture less lines on the Imatest chart.
I do not have a current copy, but if you posted your results, doubtless they could be analyzed by someone who has the software up and running. I believe you could even get a trial version for free.
As to printing size, one can use a 3 Megapixel camera to print perfectly good billboards to be viewed at a substantial difference over a freeway. It's all a matter of the angle subtended by the detail in your eye and what's needed to discern the picture content.
Subjectively, I too have been surpassed by people's skin color with some cameras when there are a mix of skin types including the red skin of alcoholics, the red skin of Rosacea or odd makeup or skin oils that show metamorism.
As to color, there's a lot beyond the standard test charts to consider. Some colors, appearing to us as pink, for example, might have a lot of other components we don't appreciate and so the camera might be fooled. I've a pink-orangy flower which never comes out right on my Ricoh GR at sunset! Now that's the only occasion it gives weird colors. If your camera is more sensitive to UV or IR reflections in your environment, these factors can also skew the subjective results.
Frankly at party receptions with varied light, I will take multiple gray card pictures all around the room as light can vary within a few feet sometimes.
Now why your D4 behaves like magic, I have no idea, but likely as not, there's some systematic error with your D800 because of they were off as you describe all around the world, folk would not be quiet and DXOmark results would be abysmal.
I believe your experience with the D800 has been less than you want but I'd rely on objective measurement for resolution and look for the missing factor that makes the color odd.
Asher
But Asher... I never said that my (new) D4 behaves like magic... I said "it performs better than any other DSLR that i've used..." By DSLR, I by no means include MF in the comparison.
Coming to resolution, I believe that you are well aware that it is not totally depended on pixel count... no?
I mean, if it was, some cell phones would be able to print as large as 22 mpx MFDBs, which of course is far from truth... Compared to the D800, D4 has
insignificantly so less resolution at base ISO,
that no reasonable photographer would care about with only the most resolving of lenses, while with the rest of good (and expensive) FF dedicated Nikkor glass,
there is none that could see a difference no matter what the size of print... Obviously the resolving power of modern lenses is not as capable as we think...
OTOH, with D4, (if you know what you are doing - which I know you do) you can print at 36ppi output, ...while with D800 there is no way that you can print below 72... As for colour, ...forget it! D800's sensor has many colour shifts (but again most DSLRs do - D700 is one of the few that has very little), there is no way that one can have a group of people with different skin and get a decent appearance with D800... D4 is much-much better, better than any FF DSLR i've tried yet, but still, no where near to an MFDB (where the task is simple)...
By the way, D4
is (at least) as sharp as D3X with both 50/f1.4 and 105/f2.8vr at f5.6 (their best f-stop) and it does exceed D800's (plain) sharpness above 800 iso... as of DR and micro contrast, D4 is insignificantly better at base ISO and up to Iso400, ...but leaves D800 into dust thereafter.
Mind you that (as I said in the OP)
I am talking about real DR, not what the sensor can record (which seems to be equal at base ISO) ...in other words, I am talking about DR that one can turn into a print...
By the way, you call DXO results "respectable" but I've yet to see the 2 stops DR advantage that D800 has over 5Diii and more so than P45+... I guess they have to show us what they mean by "print" and "screen"... not to mention the "colour advantage" that they claim D800 has over the P45+ MFDB... To me this sounds (only to be polite) laughable! ....certainly not "respectable" anyway...