With an all-new and world's first stacked CMOS full-frame sensor, the Sony a9 looks to be a force to be reckoned with. Check out our first look video to get yourself up to speed on Sony's latest sports shooter.

We got some additional time with the camera, and captured some through-the-viewfinder video showing the new AF system in action:

We start off showing AF tracking by using the camera's 'Lock-On: Flexible Spot M' mode. This does a seemingly improved job of sticking to our intended (initial) subject. Sony claims much improved subject tracking; and our initial impressions confirm this, though Lock-on still experiences a delay in initially locking on to your subject.

We then take a critical look at AF joystick usage. The joystick allows a function to be assigned to an inward press (it's Center AF-S by default). In our video we experienced the camera misinterpreting directional pushes for inward presses, but we've subsequently found this was limited to the unit we were filming.

Lastly, we look at the newly added ability to tie a specific AF mode (with or without AF activation) to custom buttons, which is potentially game changing when it comes to quickly adapting to changing scenarios. Unfortunately, you can only ever switch to one other AF mode; but quickly switching back-and-forth between two AF area modes is still fantastic, and one of the things we truly enjoy and use when shooting high-end Canon/Nikon DSLRs.

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