Some time ago I doubted IR shooting could work on D800, having tested my single (!) wavelength filters. Just to be sure, I got a cheap 850 nm filter and tested it on my D800 today: and it worked!
The reason being, every wavelength above 850 nm goes through this filter, while single wavelengths in the IR spectrum are too weak to be detected.
Pictures can be converted to black and white only, no blue skies, due to complete absence of red green and blue. Here below the procedure how to work with pure infrared pictures on D800:
White balance: take a picture of grass only and use it as white balance, or just leave the AWB on, anyway you cannot play with colors at this wavelengths.
Focusing the subject: choose film mode live view, max aperture, max ISO, shortest time, press AF-ON or equivalent until you focus – it will not work in cloudy dark days. Without autofocusing through the IR filter, focus cannot be sharp due the different length of IR wave and visible light waves.
Autofocus: turn it off, once focus is setup
Aperture: choose the soft spot of your lens to increase sharpness, as IR pictures are already quite softy
ISO: the lowest the better, around 400-1600 it works good
Time: not longer than 15 secs or in the center of the 50 mm f/1.4G a light spot will appear – although it looks like it depends on the light source location
Finder: close the light path or any light will generate stripes on your picture
Shooting mode: 2 secs delay to avoid vibrations
Enjoy pure IR shooting with your D800! Notice the dramatic difference in light emission of same subjects in the sun or shadow by comparing picture 1 and 4…
… and also, large leaf trees look like reflecting more IR than needles of pine trees (figure 2 and 3)