Watching the 2nd video. Nice stuff but right at start someone asks, what happens when you change little of your composition and he is like you have to make sure you don't as he using eTTL and Av mode. If you change horizontal to vertical or your shooting position or zoom in, eTTL and Av mode going to change flash as well as ambient exposure. So he says in that case I will move to manual exposure. So my rookie question is why not be in manual to begin with? That older gentleman he is trying to shoot is not moving, lighting is not changing, so why eTTL or Av mode?