My husband got a Canon SL1 for his birthday. He has the kit lenses that come with it, 18-55 and 75-300. I know absolutely NOTHING about camera lenses, and he is really just getting started with photography other than a point and shoot, so he's not exactly sure what it is he wants/needs. When he was taking pictures on our last vacation, he indicated he wished had a lens that was somewhere in between these two for zoom? Does this make sense? Can anyone help me out with a recommendation as to what may be a good fit? And a few other stupid newbie questions....are lenses interchangeable with brands? meaning do I have to buy canon lenses for this camera? He mainly takes pictures of vacations, not much action shots. Thank you!!!