I'm having another strange flash experience with my G6. Ive just set it to second curtain sync otherwise known as rear curtain sync. I did a long exposure and to my surprise, the flash fired at the beginning of the exposure certainly not what I was expecting. Though it also fired at the end of the exposure as well. Don't suppose the first flash was like a pre-flash or something like that but it was pretty bright. Looked just as bright as the second flash.