So it seems that I am not the only one who has had this issue with the sb900. Apparently it affects the sb700 as well. With the AF assist light on the sb900 mounted on my d700 and confirmed with my d90 as well, my images are back focused. I am going to try it on another lens since it seems to be an issue I've had with my 35 1.8 g ( on the d90) and my 35-70 on the d700. My 80-200 didn't have this issue and it seemed to be sharp all the time. I also rented a 24-70 2.8G that didn't have the issue as well. I will double check later on with the rest of my lenses. I bought the sb900 to add to the 800 and it can be used as a commander on the yn622n's. Has anyone else had this issue? I have my 800 to hold me over but I am contemplating getting another sb800 or replacing with another sb900. So my question would be, if you were in my shoes, take another gamble with another sb900 ( I am sure some folks don't have this issue ) or just replace it with another sb800 and get an external battery pack like a quantum or a godox ( cheetah) or whatever the brand? Or just shell up the extra 200 and get a 910.....But I have seen some folks with the same issue but not mentioned as much as the 900. And by the way- with the af assist light off on the flash, focus is spot on all the time. Edit- tried with the 50 1.8g and inconsistent. Some are sharp and some aren't in AF-S and in AF-C spot on. And I was shooting at F3.5-4. I also mounted it on a yn622n and same issue with the AF assist pattern. I shut it off to see if maybe it would just emit from the trigger but unless I'm doing it wrong- when I turn it off from the flash- it doesn't emit from the trigger either. Nonetheless, inconsistent focus with the sb900 and its aF assist light on in AF-S I don't mind retiring it as an OCF but I was hoping to use it on camera as a commander with a wireless set up.