Welcome to my Sony a6400 Gallery. This little camera has an excellent APS-C image sensor, blazing fast autofocus and unbelievable AF tracking. It's a great small (but very powerful) camera to keep with you for travel or any other purpose.
I had the a6000 in the past (gallery) and was not happy at all with the very slow startup time and the horrible 'PlayMemories' built into the camera. It made the camera slower and the menus more of a problem. Fast forward to the a6400 and now we see the same type of menus found in the a7R III and other recent cameras that (fortunately) ditched PlayMemories. That's a good thing! :-)
Unfortunately, like the a6000 I tried in the past, I just couldn't get used to the a6400 and while the AF is excellent and the image quality is great, the body is just lacking basic functions you'd expect at this level, like a front dial. I ended up returning it in a short time and replacing it with a Fuji X-T30 (the baby X-T3).
I have some full resolution ISO test photos HERE.