Since setting up the photobooth before a wedding reception is not really the kinda thing you want to do in a suit and tie, we often find ourselves in a position where we need to change clothes, and don't have access to a convenient place to change.
Sometimes, vacant parking lots located a little ways off the main road work out as great places to change. And yes, I suppose changing in a bathroom at the reception hall would be the normal thing to do... but honestly, would that be as much fun?
