I'll know soon enough. Ordered the Tam 150-600 in Sony A-mount for the A7Rii. I did watch T.Northrups review pitting it against the Sigma 150-600, the Canon 400/5.6 and the Canon 100-400ii. The bottom line is that they are all sharp, just minute varying degrees. Chelsea liked the Tam 150-600 due to weight alone, their sidekick on the review liked the heavy beafiness of the Sigma. I've got the 100-400ii already and it is a cracker lens but even with the latest Metabones it and my other EOS long lenses are not what I want on my Sony. So I rented the Tam in the Sony mount and was impressed, enough to add it. Not perfect but on the Sony a push of a menu button and I can be at an effective 900mm.