Liveview AF not working? i have a nikon d7000 and a d3200 with a sigma dg 70-300mm f4-5.6 lens, when i try to focus through the viewfinder it works perfectly on both of them but when i try to focus in liveview neither of them can, they just move the focusing ring slightly closer every time i half press the shutter to focus, although when I tried the lens on a friend’s d…