Olympus 100-400mm IS VS 40-150mm Pro, which one?? – RED35 Review

Preorders:
Olympus E-M10IV at Adorama, Bhphoto. GetOlympus. Amazon.
100-400mm at Adorama, Bhphoto. GetOlympus.

If you don’t know which one is best for you check out the video from RED35: