best light source

[igus mikler]

hey. preparing for a shoot daytime to night. where the music band and camera will be on an open truck and will be in motion (slow speed) want one frontal light that I will diffuse. But since will be on a truck driving around town all day (no power supply) what light would be strong enough and give daylight - I am thinking a small HMI- with regular (cheep) generator (but that is a problem when we also need the sound for the band to hear the music.

This will be shot digital- so dont want to blow out the background.

would you think a regular white bounce card would do the trick? but still need some light for shooting at night.