When I work as a wedding photographer in the church I use two camera houses with different camera lenses attached on the bodies. It allows me to quickly change focal length without any delay or unnecessary clang. I am the first person receiving the bride and her father in time of the church. In an image that Johan Rosén has taken of me dressed in black, you see how I stand ready with two Canon digital SLR cameras.
I have a Canon Speedlite 580EX II flash mounted on each camera. Now I do not use the flash in each picture, but I try to vary the motives as much as possible. When I use flash light I try to bounce the light to any wall or ceiling as much as possible. In these pictures, I used the following settings on the camera; ISO 800, f/2.8 with a shutter speed of 1/40. As you can read in settings that it was the pretty dark in the church.
It pays for bride couple to move slowly in the church. They will get more and sharper images. If it goes too quickly, it is difficult to obtain sharp images specially whether it would be dark in the church. And a wedding photographer have time to perpetuate any event during the ceremony.