External Flash for a Homecoming Dance?

I was asked to shoot a high school homecoming in mid October. I know the venue will be poorly lit so I would need to use an external flash, correct? I shoot with a Nikon D3100, so I'm thinking high ISO, manual, but unsure about the lighting issue… Help?

400 ISO is fine with a nice mid-level external flash. You should get good exposures from 20 to 25 feet away, and of course much closer. You do not need manual settings for this event. Your biggest challenge might be recycle time and battery depletion. Be prepared with extra accessories such as storage card, camera, and flash batteries. Some flash units allow for the connection of an external battery pack. Maybe a local camera store can rent a flash and battery pack.

Watch out for people wearing white. The images will under expose unless you compensate.

External flash should also help with red-eye problems because it sits higher on the camera. If your camera syncs at some slower shutter speeds, the ambient room light will become visible in your shots. Be careful, however, because there could be some image blur even though the flash speed is in the 1/000 or shorter range.

One more thing. Maybe you are doing this gig for free and that's okay, but ask the requesting party to pick up your out of pocket expenses. School homecomings usually budget for photographers. Pack a tripod.

I've done proms for over thirty years and yes, you would need to purchase or rent an external flash and a modifier for it. You could just bounce your flash off a white index card rubber banded to the flash head. Do not use a super high ISO or you will get noise. Manual is unnecessary, tripod unnecessary.