I noticed my shots are backfocused when I use SB-700 or SB-900 flash in dim light where AF assist lights UP. I'm using Speedlights mounted direct on camera hot shoe.
I have also discovered my shots are focused spot on when I turn off the AF assist light in flash menu. I have D700 with MB-D10 and Nikkor 24-120/4 VR, Nikkor 50G/1.4 AF-S, Sigma 85/1.4 HSM, Sigma 50/1.4 HSM lenses. This issue is present to some extent on every lens.
Lately I have found it's more visible on the non-cross type AF points, but on the cross type ones it's OK with SB-900. With SB-700 is backfocus present on every AF point, but on the cross type ones to much lesser amount. Camera is still able to achieve focus when I turn AF assist light off in flash menu, but it's slower so I would be glad if I can use this feature.
Is anyone experiencing same problem with Speedlight AF assist light and is there any solution to this? I was told in service they never heard about such problem :-(
Thanks for answers :-)