i need some help with my d800. it is back focusing, usually around 10-20 ft. multiple lenses and with any settings. but most prominently with the sigma 50mm 1.4. i have been using the camera for about 4 years, and never had this problem untill recently,about 15,000 shutters. i took it to a camera shop, the service guy took a few in focus pictures with it and said he has no clue...

so wtf is up? anyone else have this problem?

>pic unrelated