Really want to get to know more about lenses I own a Canon vixa hf g10, I mean there is so much out there to learn I guess my real question is what's the diference some lenses? is the Iris on some able to open and shut further then other lenses? What is considered a good lens when measuring in F Stops? any kind of info would be appreciated, I tried looking it up on my own but am having trouble expressing what i want to learn in the google search bar.