I have a Canon 350D and want an everyday lens. I'm considering: Tamron 28-75 Canon EF 28-105 Canon EFS 17-85 IS Canon EF 28-135 IS How much faster is a F/2.8 compared to a F/3.5, or F/4? Will F/4 be ok for evening use? Also does IS work very well? My 350D is very light and probably would need it. I'm coming from kit lens so anything will be better Or maybe suggest me buying 2 lenses to handle that range, for about the same price.