I´m using a Tamron 150-500 mm G2 for my Zoo, Wildlife and Sport photos. As a CameraI have a Canon 7D Mark II. I´m really satisfied with the combination. The Speed of the lens fit with the camera speed even on high speed mode 10f/sec. For scenic photos I using my Canon 7D with a Canon 24-105mm USM IS Lens. A fantastic combo
My big doubt, it's Sigma Contemporary better than Tamron G2 in general performance, or not? My camera is Canon 80D by the way.
I have not used either lens, but my instinct tells me Tamron G2 is better than Sigma Contemporary. As you probably know, Sigma has two versions and the Sport is the more professional (the Contemporary is the lower end). I think the Sigma Sport is likely comparable to the Tamron G2 but the Contemporary is beneath both of them in build quality and sharpness.
