Most of the digital camera comes with attached flash guns albeit not sufficiently powerful. They do come with hot shoes too. Can anyone use any external powerful flash guns with a digital camera? For example, I have a small (pocket size) flash gun and one heavy Vivitar make flash gun, both of which I used with my earlier analogue cameras. Can I use them with my Cannon Powershot S5 IS? Cannon company seem to advice to use only those flash guns made by them!!