Hi Nabu thanks for your answer. I tried to make it work the way you said but the bullet behavior is messing up. I cannot make the camera object go to the position I want it to be.
By the way, I made two instances variable attach to the camera object to track its position. PosX and PosY, I simply add the number of pixel to this variable to keep it updated (not sure to be clear). I'm not comfortable with the arrays.
Anyway, if you have some spare time I would gladly see an example of yours. Thanks again.