I'm obviously late seeing this thread (only about 3 years:)), but thanks for your post @HockeyFan12- very helpful info. I have a Canon C100 mark i and have to shoot some handheld tennis footage and looking for a lens that's relatively light with fairly quiet and fast AF & IS. Are you still a fan of the STMs? Good to hear you especially like the IS on the 55-250 STM since I'm looking at that one, though I'll be shooting some stuff behind players on the court so may need something wider. I'm also looking at the EF 24-105 f/4 L IS II though I'm not sure if the IS & AF are as good/quiet as on the STMs or whether the image is significantly better to justify the higher price. If there's a lens suggestion that springs to mind for what I'm doing, I'd love to hear your thoughts.