You can get a new Canon 70-300mm f4-5.6L IS USM for $1350. Add a Metabones auto focus adapter and you are ready to go with one of the sharpest zooms on the market for about $1750. I see the Amazon price for the new Oly 300mm is $2500. Both lenses are weather and dust sealed. I have been using the Canon/Metabones on my em5 Mk ii for a few months now and continues to operate fully as if it were a native Olympus lens. EXIF data, auto focus through the full aperture range, just a great combination. The one feature it does not support is continuous focus. Considering that you can pick up a near mint 70-300mm L for around $850, it makes the Canon/Metabones combo a great option when looking for exceptional glass out to 300mm range. I've seen the reviews and posted images of the new Oly 300mm and they all look beautiful I am certain it will be a great lens. $2500 for a single focal length it above my price point. But for those with the money, I'm sure it will be an enjoyable ownership experience. Don't discount the exceptional Canon lenses out there with the Metabones adapter as an alternative.