How do you take a group photo of about 70 people in a night environment? How much lighting do you need to get it done?
I was thinking of how to shoot this group shot, and in the end, I used 4 strobes at 1/2 power each to achieve this shot. A wide angle lens was used (12mm @ ISO640 + f/8 + 1/125s), and I was in an elevated position shooting downwards. There was one strobe at each side of where I was standing, with a silver+white reflective umbrella. On the photo left, the white wall was used as a light bounce, so a flash was shot at the wall. On the photo right, another strobe with a reflective umbrella was used. The silver reflective umbrellas give a nice contrasty look to the photo.
The final result is what you see, and I was quite pleased with the results... but there are still some shadow areas cast on a few faces. I could have placed a 3rd strobe in the front, but aiming it further towards the back, or shifted the side strobes higher. Anyway... you can see the rest of the group photos here.