Has anyone used the Sigma 70 mm/2.8 macro on a FF camera ? I'm moving to a 6D or 5D for "surface photo reasons". I have the 100mm L macro, but would also like to have something with less mm and the 70 mm has good reviews. The macro side of FF is giving me some headace as I have read that the DOF is much less on FF ( I currently use a 550D w. 60 and 100 mm macro). Any comments on that ? Has anybody had second thoughts after moving to FF ?