[Denant]

I bought the SB900 recently for my D700. I found it will affect the focus of my Sigma 24-70 2.8 EX DG Macro. I tried newer Sigma lens e.g. the HSM ones and also the Nikon lens AF-D or AF-S, the focus functioned well and sharp. But when I used back the Sigma 28-70, the photos were out of focus. Can any C Hing help or give advice?