Quote: What is the best ISO to use on a Nikon D40, with Nikon SB-800 speedlight, without a tripod for a wedding in a register office and outdoors? ISO 200 or ISO 400? And what is the best aperture to use? I photographed my other 2 weddings with a fully automatic film SLR, so my next wedding will be my first with my new camera.
My opinion? The lowest you can safely use. If the light/flash allows 200, use 200. I haven't done a digital wedding, but in the old days of film that was always my motto. When it comes to enlargements the lower the ISO the better.
Oh, and if you are using the kit lens and it's in a church or old registry office the chances are more likely that your choice will be using ISO 400 or 800 inside, not 200 or 400.