COLOGNE—It's been a long-standing rule that you need to make a choice when it comes to digital photography—you either get a top-end SLR that supports an incredible burst rate, but at a relatively modern megapixel count, or you can go with a high-resolution camera with a modest burst rate.

Sony's long overdue update to the full-frame Alpha 99 doesn't just break that rule, it shatters it. The SLR (or SLT if you want to argue semantics) shoots at up to 12fps while tracking subjects, and it does it at 42MP in Raw, JPG, or Raw+JPG format.

That's an incredible feat unto itself. It gets there by leveraging what's arguably the best 35mm image sensor on the market, the same 42MP chip used by the Alpha 7R II. That gives the camera access to on-sensor phase detection, which is coupled with a dedicated autofocus system with its own phase detection points. Working together, the hybrid focus system boasts 399 individual focus points, covering 47 percent of the surface area of the frame. To compare, even the Nikon D5's 151-point system only covers 21 percent of the frame.

Despite having such a beefy focus system, the Alpha 99 II isn't a huge camera like the D5. Sony says that it's roughly the same size as the Alpha 77 II, which seems right to me, as it felt very much like the similarly sized Canon EOS 7D Mark II and Nikon D500 in my hands.

That may be a turn-off for pros who are used to a larger camera, especially when paired with a big telephoto lens. I only had about 15 minutes to give the 99 II a test drive, along with the updated version of Sony's 70-200mm f/2.8 zoom, but I've used bodies of similar size and weight along with longer telezooms like the Sigma 150-600mm Contemporary in the past.

I'll pass on a final judgement until I've had more time with the camera, but my initial impression is that it seems like a fine size, and one that will actually be appreciated by nature photographers who need to schlep camera gear into the wild. And the Alpha 99 II is a good choice for location shoots, as its sealed body is protected from dust and moisture. Feel free to take the camera out into the rain in hopes of getting a shot of some elusive critter.

Sony set up a small studio with continuous lighting and a few sets of dancers in a conference room in the Koelnmesse convention center at which Photokina is held. I went for tight shots at 200mm to stress the focus system as the dancers moved through the frame. I also tried to switch the camera between the two moving dancers, who were different distances from the lens for the most part, to see how quickly the focus system kept up. I was shooting with a pre-production camera, and wasn't allowed to remove the memory card to look at photos critically, but reviewing shots on the rear LCD showed that the Alpha 99 II has a pretty solid hit rate. Again, further testing is required to get a real handle on how it compares with the top-end competition.

Electronic viewfinders don't have the best reputation, but that's in large part to just how underwhelming early EVFs were. The Alpha 99 II uses the same EVF that you'll find in the Alpha 7R II, and it's one of the best in the business. It's big to the eye, refreshes quickly, and previews exposure and depth of field in real time. When shooting at 12fps you do have to deal with black out, however, which can make tracking moving subjects a challenge. Like the smaller mirrorless Alpha 6300 you can set the A99II to shoot at 8fps. When shooting at that more modest (but plenty quick) rate you'll see an image in the viewfinder between exposures, so you can better move your camera to keep up with a moving target.

Focus during video is just as quick as it for stills. I set the camera to record and played close attention to its focus system as it subjects moved through the frame. Subjects were kept in focus, even as they moved, but again, further testing is needed to see how the camera performs in various real-world situations. The buffer is big enough to shoot for about 4.5 seconds when shooting in Raw mode at 12fps—about 54 images—and just a bit longer (60 shots) if you opt for JPG capture.

You can read more about the Alpha 99 II in our initial announcement story. It's set to ship in November and is priced at $3,199 as a body only.