Am wondering if any one uses the 70-200 f2.8 vr I/ii or the 70-200 f4 on their travels o/seas. The f4 is lighter, however are the optics as good as the F2.8? Would like to hear what people think as I would also be taking 16-35 f4 and the 24-70 f2.8. Will be using d800.