I was thinking of buying a nikon speedlight SB900. I havenot bought it yet and was just researching what all i can do with it. On one of the links I read that when u r firing SB900 off camera (wireless)... the inbuilt flash on the camera also fires. I have a D90 1)so I am confused that if the flash on the camera will fire wont it ruin the exposure or am I wrong in understanding this? 2)Another thing is how can u prevent from firing this inbuilt flash while using SB900 in off camera mode. 3) If we can not prevent from firing this flash how can we avoid affecting the exposure?