Grahame wrote:
Place the camera on a tripod in daylight outside. Set the camera to 1/400s, f/8, ISO 100, AF single centre focus point, IS/VR Off. Aim it at a good target, contrasty with edges, with centre focus point over this. Take a shot using the self timer.
If the image is in focus and sharp where the focus point was your camera is good. If not, you need to post the image for further diagnosis, or any others you consider "not in good focus" as examples.
👍👍👍 The FE 70-300 G (I own) on that camera which I use to own (now own the a6500) is the equivalent to a 140-450mm You need to be generally using a shutter speed of at least 1/500 sec to prevent motion blur. With the lens I usually use spot or center with autofocus set to AF-C (continuous) vs single. If all else fails, go to green auto mode.