My guess is you will not be able to focus it accurately enough to achieve satisfyingly accurate and precise manual focusing results if the lens is used at wider f/stops...even f/2 is dubious, in my experience, in many situations that are even the least bit non-static. Why? It's the viewfinder screens in d-slr cameras! These viewfinder screens do NOT, I repeat, they do NOT show the limited depth of field of wider aperture values; what is seen through a modern d-slr screen is roughly around f/4.5 depth of field wise...which means that what you see, visually, is NOT as crisp and as IN-focus nor as OUT-of-focus as you'd see with say a 1970's or 1980's manual focusing SLR's viewing screen. You're focusing by eye with basically moderate aperture depth of field, but if you happen to be photographing at say f/1.4, the chance for focusing boo-boos is wayyy high. If the subjects are moving, then the problem just gets worse and worse.
And as Tirediron mentioned, 50mm? Not that useful as a studio lens length! I'd want something longer, like maybe the Cosina/Voigtlander 58mm f/1.4 for a specific example. 50mm forces you to be sooooo close to people...the distortion of the body and features is pretty apparent, compared against a longer lens length. Outdoors, in real, actual social situations is where the 50mm lens shines, but honestly, I think the newer autofocus lenses are the smarter bet for more situations; you will find out soon enough that with a D800, if your focus is not EXACT, that your 36MP camera's photos look like they were made using a 10MP camera. Focusing is becoming more and more and more of an issue as MP counts soar.