higher speed focusing in very low light with a D700 and SB800 flash ?
im not a driver so sorry i dunno :(
I am pretty sure there is an AF-Assist Illuminator on the SB-800. Make sure your camera is not in continuous focus mode and that the center dot is chosen for focusing. Then the flash should emit a red light allowing you to focus in total darkness. I know it works with my SB-900 and my D700. If you have any questions, shoot me an email. Best wishes.
