The darkness of January has been lightened by the prospect of Firmware 3.0's Centre Scan. I'm shooting a doc (mostly on the Sigma 18-35) and being able to punch in when needed, will be really useful. I can see how to change to centre scan in the menus but obviously this is way cumbersome. There doesn't appear to be a way of assigning it a button. Or is there...? Any wisdom gratefully appreciated...