The Gary fong Lightsphere is great for smaller rooms and when the subject is close to you. It gives very natural results. However, for the wedding in a large reception room with high ceilings I would not recommend it. Too much light is lost around the sides and back of the sphere that would have no effect at all in a large room like that. Especially using your SB600 which is not all too powerful to begin with.Originally Posted by melaman
I would suggest just using a bounce card secured to the flash. A large enough one will throw alot of light forward. The light going up towards the ceiling will be enough to give some nice ambient fill.
Another thing is that if your going to rely on the cameras metering system to put the correct flash output you may have a bit of trouble unless you specify your subject and lock Flash exposure on it.
I have good results from my 5D by spot metering and using FEL (flash exposure lock) on my subject just before snapping. Great consistent results, whereas just using evaluative metering and letting the camera decide whats right can give you a mixed bag of very poor to ok results.