my suggestion is there is no hard fast this is what happens with fireworks rule. As stated by another, ISO 100 f11, yes, that is a good starting point, but what works at the beginning does not work in the finale. Throughout the course there will be big flashes of light, lesser flashes, then a big one followed by little ones. I was ranging between f8-f22, and from about 10 sec to 30 sec last night (ISO never left 100). So yeah, f11 is a good place to start, but, depending on where the display is, and the surrounding light, size of display, and overall creative effect ---f11 is a good start, but play around!!!