Hi, I'm taking a big group photo - abt 90 people at Sentosa for my company retreat. The photo will be taking in the morning, at 8.30AM in front of Rasa Sentosa hotel (next to swimming pool). I hv not done anything like this before. I'm thinking to hv 7 layers and each layer consists abt 18 people. Would that be any problem? And what aperture should I used to achieve perfect converage? Pls advice.