Whatever it is. The fact here is, you are shooting indoor. And are the lights in the ballroom going to provide you with lights as bright as daylight?:think: i doubt so. Yes, you might say the ISO may be able to compensate on your end of pushing your camera to take faster pics. However, do not be surprised about taking shots as slow as 1/10 at f2 with flash on. If i were you, I would have told my chairman, there are only 2 options for him.
1) Give me a free entry + cash for me to rent a flash; then you will appear for the event.
2) No free entry + no money to rent flash. You will not be going for the prom night.
I believe since they are working on tight budget. They would require as many people to attend as well as to pay for thier entry fee to cover cost. 1 person out, means one less amount to the amount to cover cost.:devil: