Question about lenses... I own a Nikon D7100 with a 16-85, a 50 1.4, 70-300, a 105mm f1.8 AIS lens. thinking of getting the 10.5 fisheye or the 28mm 1.8g, I tried the 10.5 , but it had issues with a extremely tight focus ring while on the camera, off the body it was fine. The 28 is a FX lens but could be used for DX as well. Any feedback or experience with these lenses would be helpful, thanks much.