...I do think the Tamron handles the transition from focus to defocus more smoothly than the Canon.
I was never pleased with the (latest) Canon's rendition of transition areas; went from busy to garish to, "what's that other stuff in there?"
I'm thinking of getting this Tamron in F mount to replace or complement my Nikon 70-200/4vr. Also a very sharp lens but suffers from similar transitional area bokeh ugliness. (but it's so small and light..)
Wow, I never thought I will hear this about 70-200 mk II (I hope you guys are referring to that lens) which some here (and elsewhere) consider to be the best canon zoom lens made till date (it surely may be so)! Now day by day my itch of buying the Tamron 70-200 grows exponentially. (now the rose petals will suffer) I should buy it now, I should wait till next year, I should buy it now, I should wait.........
That's the one.
Canon's lens (& Nikon's) may be incredibly sharp and very well corrected for the focus plane, but the out-of-plane areas can look like garbage in some conditions.
see my e.g. here, look at the R side of the apple on the R side and tell me that's a nice bokeh rendition of the branches behind it. www.canonrumors.com/forum/index.php?topic=819.210
I've had many shots with busy backgrounds made more ugly by this lens so I got rid of it.
I posted a similarly ugly shot from the Nikon 70-200/4vr somewhere too.
A good lens is not always about ultimate sharpness, those other areas matter too. (Also, Canon's 70-200/2.8L IS 2 has a fair bit of CA in FF corners)
I really like what I saw when just quickly testing the Tamron. I can see the Canon and Nikon lens trouble areas just thru the viewfinder while racking focus over busy backgrounds. Do that w the Tam and you won't see nearly as much of that radial bokeh
I'll trade ultimate sharpness for a better-balanced performance on pretty much any lens. As such, I sold my Canon 2.8 L 2, have been still using my Nikon kit for now and will likely add this Tamron in the future.