is it a good idea to change the lens for a Canon EF-S 17-55 mm f2.8 is USM. gonna pick up the lens tomorrow but i can still change it. it is brand new in his box at the shop so....
the only thing im afraid is that the auto focus is a bit slow and f4...... over a f2.8.......
if im shooting 90% day and 10% night..... 24-105mm can hold it???