Hi Everyone, I was hoping to get some advice. this is my first post. 90-95% of my photography is around getting the absolute best candid and portrait shots of my friends and family either at events or travelling. I have a Canon 20D and bought the 17-85mm IS lens thinking this would be the perfect multipurpose lens for me. It has been fantastic. The range is great and IS is fantastic for me (I drink lots of coffee - I am very very dissapointed with the lack of background blur (bokeh) capability of this lens. I love this aspect of photography. I love the 3D effect created by it. So I want to ebay this lens and am looking at either the 24-70 2.8L or the 24-105 4L. I'm leaning towards the 24-105 4L for the range flexibility, lighter weight and IS capbility, but am really woorried that an F Stop of 4 will still not produce the kind of background blur I love in most sitautions. Any help you can offer would be greatly appreciated?