I am going to be shooting during the day outdoors, and want to use a shallow depth of field with my f1.4. However, I can only shoot at a max of 1/4000th of a second. If that is still overexposed, am I correct in thinking that I could use an ND filter? That way I can retain depth of field but cut down on the amount of light? Would a polarizer help as well ( how many stops do they typically cut? ).