If I were to invest in a flash for my 400D would you suggest either the 430EX or 580EX or indeed any other.....(to be used in low light indoor situations only).
Or would I not really notice a difference from the 'on the camera flash'
You'll notice a massive difference with a proper flashgun. I've got a 430 and it's great. The 580 is more powerful and has a few extra functions afaik, one of which is a strobe mode. It's down to cost really.
