ive just recently got into skateboard photography and low light situations are a bit tricky for me. i know how to find great angles and i can shoot farely well when the lighting is great but ive never used a flash before and i wanted to start getting into it. i dont know much about flash photography. i have a vivitar flash with a hotshoe but the camera doesnt read the flash. the flash will go off but my light meter doesnt recognize the flash is there. i dont know if thats normal or not. preferrably id rather not have to burn through a bunch of rolls to dial it down. are there any basic rules i should follow? i read a bit about guide numbers for flashes, how i should take the guide number, divide it by the distance of how far my subject is and use that for the aperture number. i dont know if thats for skate photography though.