if u use ETTL, the flash actually fires 2 burst when you release your shutter. The first flash is reflected off your subject, back to the lens and is used by the body to compute the flash power. This info is communicated back to the flash which then fires the 2nd burst for the actual exposure.
All this happens in a blink of an eye :bsmilie: so you sometimes cannot see it!
I usually FEC +2/3 to +1 if I bounce. Bouncing is an art I feel cos the angle needs to be right as well, otherwise some parts bright, some parts dark :sweat: