Yup, I know, it isn't a Canon review or a lens that will fit on Canon but the review is worth reading as both the reviewer and site owner are willing to experiment with new equipment, even if it means not getting the shot, e.g. from the review:
Last year Michael used the Olympus E-M1 in Antarctica and missed some crucial images because he was using 4/3 lenses that did not use the Dual Phase-Contrast auto focus. By the time the lens focused, the shot was gone. This was most noticeable when shooting a whale breaching against a dark ocean background. I am convinced with the 40-150mm and 12-40mm Olympus Pro Lenses that this kind of shot won’t be missed this year when I take this gear to Antarctica.
... it is reviews like this where you find people talking about the bleeding edge of photography - included what blood was drawn!
It's great to see the potential allowed by not only a smaller sensor, and mirrorless. That will keep improving rapidly, as happens with electronics.
But you've got to wonder, what would a EF 80-300/2.8 look like?
and how big would it be, etc?
The 40-150/2.8 lens on M43 would give a broadly similar depth of field to an 80-300 lens on full frame. The light needed to get the shot at f/2.8 on M43 would be vaguely similar to that needed for f/5.6 on full frame, given the extra high ISO performance of a full frame sensor compared to M43. So to achieve broadly similar goals, the equivalent lens would be an 80-300/5.6 - that is not far from the spec of the 70-300L.
That exists already, is just over 1kg in weight, much fatter than the Olympus, but not hugely different in length. Canon have done an amazing job of giving that amount of reach for full frame in a reasonably short package. I love mine, but sometimes wish it wasn't so conspicuous.
Perhaps there is a market for an EF-M (or EF-S) f/2.8 telephoto zoom to compete with the Olympus?