Welcome to Mossberg, a weekly commentary and reviews column on The Verge and Recode by veteran tech journalist Walt Mossberg, now an Executive Editor at The Verge and Editor at Large of Recode.

Welcome to Mossberg, a weekly commentary and reviews column on The Verge and Re/code by veteran tech journalist Walt Mossberg, now an executive editor at The Verge and editor at large of Re/code.

Now that Microsoft’s Windows 10 is here, hopes are running high among PC makers that their laptop sales, which have been declining or flat for years, can be revived.

At the same time, these hardware makers are hoping to nudge Windows users into the $1,000-plus category traditionally dominated by Apple, since margins are pretty thin on the more typical $600 laptops.

Many OEMs are relying on touchscreen designs that allow laptops to double as tablets, either via flip-around hinges or detachable screens. Microsoft itself is launching its first laptop — with a detachable screen — the sleek, handsome, 13.5-inch Surface Book, due out October 26 for $1,500.

Toshiba is taking a different approach

But Toshiba is taking a different approach, with a light, thin, 12.5-inch laptop that has a 4K Ultra HD screen, similar to those on the latest generation of TVs. This isn’t the first 4K laptop, but Toshiba claims it’s the first to be available in such a small size. It’s called the Radius 12 4K, and starts at $1,300 with 256GB of flash storage. With 512GB of storage, it costs $1,600. A version with just a normal HD screen and 256GB of storage starts at $1,000.

Though Toshiba didn’t say this, one reason for going 4K may be that convertible / detachable laptops have been around for a few years and have failed to revive the Windows laptop market. So the company may have felt something more was needed.

It’s also not a given that Windows 10's popularity will translate into higher laptop sales, despite the generally positive reaction. Microsoft — unlike in the past — is strongly encouraging users to upgrade their current PCs for free.

I’ve been testing the Radius 12 4K and I did indeed find the screen to be dazzling. It’s not only super-sharp, but has brilliant colors because Toshiba worked with Technicolor to calibrate the display. It’s also a sleek, handsome machine, a hair under three pounds. It can be flipped around to be used as a (heavy) tablet. And it’s fast, because it uses the top-of-the-line i7 version of Intel’s sixth-generation Core processors.

I compared the Radius 12 4K to two other laptops, both widely admired. One was the 13-inch MacBook Pro with Retina display. The other was a 2014 Lenovo ThinkPad Yoga with a 12.5-inch screen.

Screen shots taken displaying the same 4K image on a MacBook Pro with Retina display (inset) and the Radius 12 4K.

When it comes to pixels on the screen, the Toshiba beat both, hands down. Its screen offers a resolution of 3840 x 2160 compared to 2560 x 1600 on the Mac and just 1920 x 1080 on the Yoga.

But I also found some significant downsides. The really bad news: Battery life is poor, presumably because it takes a lot of juice to drive all those pixels. Based on my experience, this laptop could never get you through a work day unplugged.

Also, like so many Windows laptops, its trackpad is jerky when used for scrolling. I — and other reviewers — have been complaining for years about this, especially since Apple’s trackpads are smooth as silk. It’s 2015 and we are on Windows 10 and this is a $1,300 laptop. But the problem persists.

Like so many Windows laptops, its trackpad is jerky when used for scrolling

More importantly, I’m pretty sure most average users won’t get much value out of the 4K display, at least today. To my eyes, even the carefully selected 4K images Toshiba supplied for testing didn’t look noticeably sharper or better on the Radius than they did on the 13-inch MacBook Pro with Retina display, which has lower screen resolution, but much better battery life (albeit a higher price — $1,499 — for the same amount of storage and a lesser processor). This was true even when I zoomed deeply into the image.

Of course, 4K is likely to be increasingly important; Apple just bumped up its low-end iMac desktops to 4K. So, even for somebody who isn’t, say, a prosumer photo or video enthusiast, buying the Radius 4K may be a way to future-proof your laptop.

And, a test 4K video I tried did indeed look richer on the Radius than on the MacBook Pro, though not so much that an average user who wasn’t writing a review might notice.

Also, I viewed a YouTube compilation of 10 short 4K videos on the Radius using a fast network. The Toshiba showed finer details in 4K — whiskers on a tiger, crevices in rocks — than when I watched the same thing on the Mac in HD. But it stuttered all the way through, undercutting the quality of the 4K experience.

The Toshiba Radius 12 4K doesn’t just come with a ridiculously high number of pixels, however. This laptop packs in lots of other high-end features that help justify its premium price.

For instance, it supports Hello, the new Windows 10 facial-recognition log-in feature, even though it is too thin and light for the special camera typically used for that purpose. Instead, it employs a smaller infrared camera. In my tests, this worked almost every time on a desk, though less reliably on my lap.

It comes with 8GB of memory, and its screen is Corning’s Gorilla Glass, which makes it more scratch-resistant than the typical laptop display. It also has Harman Kardon speakers that the company says can adapt to whatever position the screen is in, so the sound doesn’t get muffled. In my tests, I found this to be true.

There are also a plethora of ports, including a new USB Type-C connector (which isn’t used for charging) and an HDMI port capable of 4K output.

And then there’s the Achilles heel: battery life

And then there’s the Achilles heel of the Radius 12 4K: battery life. Toshiba claims up to six hours, which is in itself a pretty low number in 2015 for a manufacturer’s claim. But, using my own battery test, the one I’ve employed for many years on scores of laptops, I got only about 3.5 hours. In this test, I disable all power-saving software, crank the screen to 100 percent, leave on Wi-Fi to collect email in the background, and play an endless loop of music.

Because I don’t expect real people to use their computers this way, I assume you’d likely get four and a half or five hours out of this new Toshiba between charges in typical use. But that’s still pretty weak. (Toshiba says the non-4K version of the Radius 12 gets up to nine hours between charges.)

All in all, I guess the Radius 12 4K might be good for photo and video enthusiasts, or anyone who wants a brilliant screen in a light laptop, or who just wants to be ready for 4K everywhere. But I can’t recommend it, because Toshiba didn’t build a machine with the battery power to support its ambitions.

Check out Ctrl-Walt-Delete