The A6400's body might be the same old, same old, but the electronics and software are new and very much improved. It has the same 24.2-megapixel CMOS sensor that we liked on the last model, but it now packs the latest Bionz X processor. That boosts the native ISO range to 100-32,000, expandable to 102,800, for one thing.

It also yields burst rates up to 11 fps with the mechanical shutter and 8 fps with the new, fully silent electronic shutter. What's more, you can fire off quite a few shots before the buffer fills: 99 for JPEGs and 46 for RAW files.

Shooting such bursts is pretty useless if the autofocus can't keep up, but that's where the A6400 really shines. The hybrid AF system has 425 contrast-detect and 425 phase-detect pixels that cover 84 percent of the imaging area. It makes better use of that tech than ever with new software borrowed from its quick-draw cousin, the full-frame A9.

Sony's real-time Eye AF and tracking features are powered by predictive and recognition AI. All you need to do is select your subject and it will lock on and hold it, and if it's a face, you'll get automatic face and eye detection. It'll keep tracking your subject, even when they look away, then lock on once they turn back. Sony said the AI system uses depth, pattern recognition and color to track subjects, all the way up to the maximum 11 fps shooting speed.

This feature is miles ahead of any other camera manufacturer's tracking/face/eye detection. I tested it with dogs, bikers and other subjects, and it helped me get the highest percentage of in-focus shots I've ever had at high burst rates, particularly with people. Obviously, it works best in good light, but I found it very effective even at ISOs as high as 12,800. That'll be particularly handy if you're trying to shoot sports in dim gymnasiums, for instance.

It's not perfect, of course. There are still moments when it loses track of subjects even though they're clearly in frame. Overall, though, Sony easily has the best AI eye- and face-tracking autofocus system on the market.

And it will only get better. Later this summer, Sony will release a firmware update that includes animal-eye tracking. Even if Sir Mewmew has particularly fluffy fur, the system will lock on its eyes to ensure the best shot. What's more, these features will be coming to Sony's A7 III, A7R III and A9 via future firmware updates. And it will benefit not just photographers but video shooters, too.

Video

Now let's talk about my vlogging issues. It might be unfair to single out this feature on the A6400 because it does so many other things well, but Sony actually encouraged this idea by publishing not just one but two videos touting the feature.

The biggest problem is the lack of in-body stabilization. A lot of vlogging involves walking around while holding a camera, often while extending it by using a Gorilla Pod or monopod. To put it mildly, without stabilization, your viewers are going to get sick. The best you can do is get a stabilized lens zoom, but that's no match for an in-body system, and many of Sony's best primes aren't stabilized.

The A6400 and other Sony cameras suffer from pretty bad rolling shutter. When combined with that lack of stabilization and occasionally bumpy handheld video, it's a perfect storm of rubbery, wonky shots. I found that the A6400 has more jello than the Fujifilm X-T3 or Nikon Z6, both of which reportedly use Sony sensors, weirdly.

Another issue is the lack of a headphone port. Fujifilm showed that's possible on a budget camera like the X-T30 by letting you output audio over USB-C, so you can either use USB-C headphones or a simple dongle. It's a bad look for Sony that it can't do the same.

Vlogging is best done with an external microphone because camera mics tend to pick up a lot of ambient noise while yielding tinny, low-quality audio. However, if you install an external mic on the top hot-shoe, it blocks the screen, rendering the monitor useless. You can add a bracket to get it off to the side -- in fact, Sony conveniently sells a GP-VPT1 shooting grip for that very purpose -- but why not just have a screen that flips to the side like the GH5 or Canon's EOS R?

That said, the built-in microphone is actually good enough that many vloggers who don't need perfect quality could use it. I recorded much of this video with it and the quality is certainly acceptable, though clearly not as good as what I recorded with my Rode external mic.

And the autofocus system is just as good for video as it is for still photography -- all you need to do is touch your subject, and the system will track it. Much of the time, it's relatively automatic -- once selected, your subject will stay in focus, which is ideal for casual video shooters. While it's not quite perfect, this is the best AI face-tracking system on the market. The result? Better photos.

Image Quality

Since Sony kept the imaging sensor from the A6300 and A6500, you'd expect the images to look roughly the same. However, Sony does seem to have improved image processing a bit -- noise is better controlled at high ISO settings, for instance. JPEG photos look great right out of the camera, though noise reduction can be a bit strong -- I'd recommend the low noise-reduction setting to minimize that.