Advice please..I have the 70-200mm F2.8 and am very happy except on occasion would like a little extra distance..ie Imperial Hill,KLAX. Thinking about the canon 100-400mm but lots of money so any advice on any alternatives ie 1.4 or 2.0 extenders which I'm told will give comparible results ?? Other alternatives Sigma etc but what would give the best results in sharpness and quality ??
Thanks in advance