I started with a Minolta and then switched to Canon. I have a nice line of Canon lenses, to include a Canon 400 f2.8 and a 600 f4, which are fantastic. I am considering switching from a 5D3 to an A9, but I am reading that the A9 will not shoot at 20fps when using a non-native lens. Can someone explain why this is the case seeing that a lens is just something that the camera sees through? Unless this is just a tactic that Sony is using to force sports photogs to use their lenses, instead of the ones they have already spent 10's of thousands on?