I know, I know another lens topic.... I think I have it narrowed down. ---70-200 f/4 L ---1.4 x converter ---400 L --- sigma 24-70 ex For basic general shooting what do you think. Most of my lowlight stuff would be stills so I would be using a tripod so do you think I can get away with the f/4? I like that lens because I think it would be a better walk around lens since it is lighter than the 2.8. I may be taking some racing shots also but I think the f/4 or the 400 will be OK (or am I on crack) I have thought about the Sigma 70-200 2.8 and 80-400 or even the 100-400L but I am not sold on those yet. Do you see any flaws in the logic???