I'm having a strange problem with shutter synchronisation on a Nikon D600 with twin YS-D1 strobes and fibre optic triggering, 105 mm macro. Mostly it works fine in macro at f22 but if I increase subject distance I sometimes get a black border on the bottom of the photo. If I open up to f16 this goes away. I'm not sure if I move farther from the subject at f16 if the black border comes back.
I have the strobes on DS-TTL II mode (red ready light). Someone just showed me that slave TTL mode gets rid of this problem (blue ready light, engaged by long press on target light button). Can anyone explain or confirm that I should be using slave TTL and not DS-TTL II mode?
Images attached: DS-TTL II mode - Slave TTL mode