ASR666 wrote:
the 100-400 is lighter and fast focusing. the push - pull zoom takes a bit of getting used to. Versatile and can be used for sports, birding. can be used hand held if you crank up the ISO a bit. Sharp, wide open.
the 150-500 is more a tripod lens, stopped down to f8 its sharp and produces good results. heavier and slower focusing than the 100-400 but you get an extra 100mm.
Thanks for your comments. I think I will wait until the Tamron 150-600 is released and reassess the whole thing again. Appreciate your input.