Originally Posted by Khun

Constant light or strobe? If you are shooting strobe and are ok with the loss of depth of field control and low light shooting, the f4 will work. Again though, if it were me personally, I would get the f2.8 24-70 and a f2.8 70-200. This allows for a great range of shots with outstanding depth of field control (and is what I personally have, well the Nikon eqiv.)