I'm not sure how, but Lenovo managed to cram a full-on desktop PC into what looks like a tiny monitor. The Ideacentre 510s is the company's sleekest and most compact all-in-one yet, with razor-thin edges and a borderless 23-inch display that makes it easy to focus on work or get lost in a movie. But although the 510s is an absolute all-star in the design department, its lackluster screen brightness, webcam and accessories keep it from being the best all-in-one value in its price range.

Design

From the day the Lenovo Ideacentre 510s landed in our lab, virtually everyone who has walked by it has stopped to stare. This is far and away Lenovo's best-looking all-in-one yet, packing a virtually bezel-less display into a strikingly slim silver chassis that gives the iMac a run for its money. However, while the iMac is aluminum throughout, the Ideacentre's display portion is made of sturdy plastic.

You won't have to make much space for the 510s. At just 20.5 x 12.8 x 1.6 inches, the PC is smaller than Apple's 21.5-inch iMac (20.8 x 17.7 x 6.9 inches), and the 0.28-inch-thin edges at the top of its display make it look like a small monitor. And at 9.8 pounds, it's also a breeze to carry around. The all-in-one's stand allows you to tilt the display from 5 degrees forward to 30 degrees back, making it easy to adjust the desktop to fit your workspace.

MORE: Best All-in-One PCs

Specs

Display: 23-inch, 1920 x 1080 10-point multitouch display
CPU: 2.3-GHz Intel Core i5-6200U
RAM: 8GB
Hard Drive: 1TB, 5,400-rpm drive with 8GB SSHD
Ports: 4 USB 3.0 ports, full HDMI, audio jack
Webcam: 1080p
Size: 20.5 x 12.8 x 1.6 inches
Weight: 9.8 pounds

Privacy Webcam and Ports

In order to maintain the Ideacentre's borderless design, Lenovo tucked the PC's webcam into a hideaway hub beneath the bottom of the display. It's a nice touch; you simply click a button, and a small brick pops out that packs both the desktop's 1080p camera and two USB 3.0 ports for plugging in accessories without having to reach around the back.

But although the pop-out camera keeps things sleek (and allows for some privacy when it's tucked away), it does have some drawbacks. For starters, having a webcam beneath your display is just awkward, and results in photos that focus more on the bottom of your neck than on your actual face. (I had to slouch to get a decent head-on pic.) The camera itself isn't that spectacular either, producing viewable but noticeably blurry photos.

HP's design on its Pavilion All-in-One is a lot smarter, as its webcam pops up from the top of the display, resulting in much more normal-looking photos and video.

The rest of the 510s' ports are in the back, where you'll find two more USB 3.0 ports, an Ethernet input, a headphone jack and an HDMI port, the latter of which allows the Ideacentre to double as a stand-alone monitor. The machine's power and display switch buttons are conveniently placed just behind the right edge, though I would have liked volume buttons as well.

Display

The Ideacentre 510s' 23-inch touch display seems to be made for movies, with no pesky bezels to get in the way of whatever you're watching. The gritty galactic action of the Rogue One: A Star Wars Story trailer looked crisp on Lenovo's PC, which highlighted everything from the individual lights on a massive Star Destroyer to Forest Whitaker's war-damaged face. Perhaps more important, the borderless display made it easy to get immersed in any videos I watched.

The 510s' screen was also very responsive to my touch, whether I was pinching to zoom in and out of websites or making ugly doodles in Paint with all 10 fingers at once.

I do wish the PC's screen were just a little brighter, however. The Ideacentre registered 249.6 nits of brightness on our light meter, which is better than Lenovo's 4K AIO 700 (230.6 nits) and our 237-nit average, but not even close to the 1080p iMac's extra-luminous 424 nits.

Fortunately, the 510s handles color quite well. The svelte all-in-one turned in a Delta-E color accuracy rating of 0.54 (closer to 0 is better) and reproduced 110.6 percent of the sRGB color gamut. That's just behind the AIO 700 (0.39, 134.5 percent) and slightly better than the iMac (2.9, 109 percent). Anything above 100 percent is quite good.

Audio

The Ideacentre's dual 3-watt speakers were loud enough to fill our 15 foot by 15 foot testing lab with music, but the results were mixed. The jumpy pop punk of Blink 182's "Bored to Death" was perfectly listenable, but the bass and drums lacked oomph, and the track's normally sharp guitars sounded a bit dull and fuzzy.

As with most Lenovo all-in-ones, the 510s includes the Dolby Audio app for customizing the machine's sound. There are presets for movies, music, games and voice, as well as a dynamic mode that automatically adjusts to whatever's coming out of your speakers. You can also access an equalizer if you're the type to fine-tune every possible audio setting.

MORE: The Best Headsets for Immersive Gaming

Performance

With an Intel Core i5-6200U processor and 8GB of RAM, the Ideacentre 510s packs a whole lot of multitasking muscle into its sleek frame. I never had to deal with any crashing or serious slowdown, even as I worked in Google Docs and Outlook, bounced among five Twitch streams and ran a full system scan all at once.

The 510s scored 5,992 on the Geekbench 3 general performance test, trailing the Core i5-6400-powered AIO 700 (10,864) while just topping the Core i5-powered iMac (5,464) and our 4,985 category average for all-in-ones.

Lenovo's desktop took 4 minutes and 29 seconds to match 20,000 names with their addresses on a spreadsheet, lagging behind the AIO 700 (3:51) and the iMac (3:49) but beating our all-in-one average (7:50).

Packing a 1TB hard drive with an 8GB SSD, the 510s took a fairly slow 2 minutes and 13 seconds to copy about 5GB of files, for a transfer rate of 37.8 MBps. That's slower than the AIO 700 (1TB drive, 60.6 MBps) and about on a par with the iMac's 500GB, 5,400-rpm drive (38.5 MBps, though faster SSD options are available for Apple's PC).

Keyboard and Mouse

The Ideacentre 510s ships with Lenovo's usual wireless mouse-and-keyboard combo. They work just fine for a set of pack-in accessories, but you might want to spring for something better.

I eventually got used to the stiff keys on Lenovo's wireless keyboard, but that doesn't mean I like them. Although I breezed through the Key Hero Typing Test at 92 words per minute with near-perfect accuracy (which is about my norm), my hands felt a bit cramped afterward.

The bundled wireless mouse is similarly hit-or-miss. The small touchpad between the two click buttons made it easy to scroll through web pages and perform special gestures, such as holding it down to activate the Start menu. But because of its strangely curved design, the mouse never quite felt cozy in my hand.

Software

The Ideacentre 510s includes a decent number of Lenovo apps, some of which are more useful than others. There's the usual Lenovo Companion hub, which lets you run system checkups, view your warranty and check for updates; as well as Lenovo Settings, which lets you tweak parameters such as display brightness and microphone volume.

The throwaway Lenovo App Center mostly just provides links to Windows Store apps. The REACHit app allows you to access cloud services such as Google Drive and Dropbox all in the same place, while SHAREit lets you easily bounce files between your PC and your phone. There's also the usual suite of CyberLink apps that come with Lenovo PCs, including PowerDVD for media playback and Power2Go for burning DVDs.

Configurations

We reviewed the lone $899 configuration of the Ideacentre 510s, which packs a 23-inch full-HD display, an Intel Core i5-6200U processor, 8GB of RAM, a 1TB hard drive with an 8GB SSHD, and integrated Intel HD 520 graphics.

MORE: Our Favorite Gaming Mice for Every Genre

Bottom Line

If I were judging the Ideacentre 510s by looks alone, I'd recommend it without hesitation. This is one of the sleekest all-in-ones I've ever gotten my hands on, with a design that's as eye-catching as it is compact and practical. The PC's Core i5 processor is strong enough for multitasking. But while the pop-out privacy camera is a nice touch, it's located in an awkward spot and takes blurry images.

At $899, the 510s is priced fairly, but it's far from Lenovo's best all-in-one value. The company's Ideacentre AIO 700 offers a rich 4K display, an Intel RealSense camera, discrete graphics and upgradable parts for just $200 more. There's also Apple's iMac, which offers one of the brightest screens you can find on an all-in-one starting at $1,099. The Ideacentre 510s will still satisfy those who want one of the sexiest and smallest all-in-ones available, but there are better alternatives for just a bit more money.

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Lenovo Ideacentre 510s Review: Borderless Beauty, Weird Webcam

I'm not sure how, but Lenovo managed to cram a full-on desktop PC into what looks like a tiny monitor. The Ideacentre 510s is the company's sleekest and most compact all-in-one yet, with razor-thin edges and a borderless 23-inch display that makes it easy to focus on work or get lost in a movie. But although the 510s is an absolute all-star in the design department, its lackluster screen brightness, webcam and accessories keep it from being the best all-in-one value in its price range.

Design

From the day the Lenovo Ideacentre 510s landed in our lab, virtually everyone who has walked by it has stopped to stare. This is far and away Lenovo's best-looking all-in-one yet, packing a virtually bezel-less display into a strikingly slim silver chassis that gives the iMac a run for its money. However, while the iMac is aluminum throughout, the Ideacentre's display portion is made of sturdy plastic.

You won't have to make much space for the 510s. At just 20.5 x 12.8 x 1.6 inches, the PC is smaller than Apple's 21.5-inch iMac (20.8 x 17.7 x 6.9 inches), and the 0.28-inch-thin edges at the top of its display make it look like a small monitor. And at 9.8 pounds, it's also a breeze to carry around. The all-in-one's stand allows you to tilt the display from 5 degrees forward to 30 degrees back, making it easy to adjust the desktop to fit your workspace.

MORE: Best All-in-One PCs

Specs

Display: 23-inch, 1920 x 1080 10-point multitouch display
CPU: 2.3-GHz Intel Core i5-6200U
RAM: 8GB
Hard Drive: 1TB, 5,400-rpm drive with 8GB SSHD
Ports: 4 USB 3.0 ports, full HDMI, audio jack
Webcam: 1080p
Size: 20.5 x 12.8 x 1.6 inches
Weight: 9.8 pounds

Privacy Webcam and Ports

In order to maintain the Ideacentre's borderless design, Lenovo tucked the PC's webcam into a hideaway hub beneath the bottom of the display. It's a nice touch; you simply click a button, and a small brick pops out that packs both the desktop's 1080p camera and two USB 3.0 ports for plugging in accessories without having to reach around the back.

But although the pop-out camera keeps things sleek (and allows for some privacy when it's tucked away), it does have some drawbacks. For starters, having a webcam beneath your display is just awkward, and results in photos that focus more on the bottom of your neck than on your actual face. (I had to slouch to get a decent head-on pic.) The camera itself isn't that spectacular either, producing viewable but noticeably blurry photos.

HP's design on its Pavilion All-in-One is a lot smarter, as its webcam pops up from the top of the display, resulting in much more normal-looking photos and video.

The rest of the 510s' ports are in the back, where you'll find two more USB 3.0 ports, an Ethernet input, a headphone jack and an HDMI port, the latter of which allows the Ideacentre to double as a stand-alone monitor. The machine's power and display switch buttons are conveniently placed just behind the right edge, though I would have liked volume buttons as well.

Display

The Ideacentre 510s' 23-inch touch display seems to be made for movies, with no pesky bezels to get in the way of whatever you're watching. The gritty galactic action of the Rogue One: A Star Wars Story trailer looked crisp on Lenovo's PC, which highlighted everything from the individual lights on a massive Star Destroyer to Forest Whitaker's war-damaged face. Perhaps more important, the borderless display made it easy to get immersed in any videos I watched.

The 510s' screen was also very responsive to my touch, whether I was pinching to zoom in and out of websites or making ugly doodles in Paint with all 10 fingers at once.

I do wish the PC's screen were just a little brighter, however. The Ideacentre registered 249.6 nits of brightness on our light meter, which is better than Lenovo's 4K AIO 700 (230.6 nits) and our 237-nit average, but not even close to the 1080p iMac's extra-luminous 424 nits.

Fortunately, the 510s handles color quite well. The svelte all-in-one turned in a Delta-E color accuracy rating of 0.54 (closer to 0 is better) and reproduced 110.6 percent of the sRGB color gamut. That's just behind the AIO 700 (0.39, 134.5 percent) and slightly better than the iMac (2.9, 109 percent). Anything above 100 percent is quite good.

Audio

The Ideacentre's dual 3-watt speakers were loud enough to fill our 15 foot by 15 foot testing lab with music, but the results were mixed. The jumpy pop punk of Blink 182's "Bored to Death" was perfectly listenable, but the bass and drums lacked oomph, and the track's normally sharp guitars sounded a bit dull and fuzzy.

As with most Lenovo all-in-ones, the 510s includes the Dolby Audio app for customizing the machine's sound. There are presets for movies, music, games and voice, as well as a dynamic mode that automatically adjusts to whatever's coming out of your speakers. You can also access an equalizer if you're the type to fine-tune every possible audio setting.

MORE: The Best Headsets for Immersive Gaming

Performance

With an Intel Core i5-6200U processor and 8GB of RAM, the Ideacentre 510s packs a whole lot of multitasking muscle into its sleek frame. I never had to deal with any crashing or serious slowdown, even as I worked in Google Docs and Outlook, bounced among five Twitch streams and ran a full system scan all at once.

The 510s scored 5,992 on the Geekbench 3 general performance test, trailing the Core i5-6400-powered AIO 700 (10,864) while just topping the Core i5-powered iMac (5,464) and our 4,985 category average for all-in-ones.

Lenovo's desktop took 4 minutes and 29 seconds to match 20,000 names with their addresses on a spreadsheet, lagging behind the AIO 700 (3:51) and the iMac (3:49) but beating our all-in-one average (7:50).

Packing a 1TB hard drive with an 8GB SSD, the 510s took a fairly slow 2 minutes and 13 seconds to copy about 5GB of files, for a transfer rate of 37.8 MBps. That's slower than the AIO 700 (1TB drive, 60.6 MBps) and about on a par with the iMac's 500GB, 5,400-rpm drive (38.5 MBps, though faster SSD options are available for Apple's PC).

Keyboard and Mouse

The Ideacentre 510s ships with Lenovo's usual wireless mouse-and-keyboard combo. They work just fine for a set of pack-in accessories, but you might want to spring for something better.

I eventually got used to the stiff keys on Lenovo's wireless keyboard, but that doesn't mean I like them. Although I breezed through the Key Hero Typing Test at 92 words per minute with near-perfect accuracy (which is about my norm), my hands felt a bit cramped afterward.

The bundled wireless mouse is similarly hit-or-miss. The small touchpad between the two click buttons made it easy to scroll through web pages and perform special gestures, such as holding it down to activate the Start menu. But because of its strangely curved design, the mouse never quite felt cozy in my hand.

Software

The Ideacentre 510s includes a decent number of Lenovo apps, some of which are more useful than others. There's the usual Lenovo Companion hub, which lets you run system checkups, view your warranty and check for updates; as well as Lenovo Settings, which lets you tweak parameters such as display brightness and microphone volume.

The throwaway Lenovo App Center mostly just provides links to Windows Store apps. The REACHit app allows you to access cloud services such as Google Drive and Dropbox all in the same place, while SHAREit lets you easily bounce files between your PC and your phone. There's also the usual suite of CyberLink apps that come with Lenovo PCs, including PowerDVD for media playback and Power2Go for burning DVDs.

Configurations

We reviewed the lone $899 configuration of the Ideacentre 510s, which packs a 23-inch full-HD display, an Intel Core i5-6200U processor, 8GB of RAM, a 1TB hard drive with an 8GB SSHD, and integrated Intel HD 520 graphics.

MORE: Our Favorite Gaming Mice for Every Genre

Bottom Line

If I were judging the Ideacentre 510s by looks alone, I'd recommend it without hesitation. This is one of the sleekest all-in-ones I've ever gotten my hands on, with a design that's as eye-catching as it is compact and practical. The PC's Core i5 processor is strong enough for multitasking. But while the pop-out privacy camera is a nice touch, it's located in an awkward spot and takes blurry images.

At $899, the 510s is priced fairly, but it's far from Lenovo's best all-in-one value. The company's Ideacentre AIO 700 offers a rich 4K display, an Intel RealSense camera, discrete graphics and upgradable parts for just $200 more. There's also Apple's iMac, which offers one of the brightest screens you can find on an all-in-one starting at $1,099. The Ideacentre 510s will still satisfy those who want one of the sexiest and smallest all-in-ones available, but there are better alternatives for just a bit more money.

THE GOOD The Acer Predator G6 fits our VR sweet-spot components into a big, distinctive case for under $2,000. Performance is great, basic software overclocking is built in, and there's a swappable drive bay in the front.

THE BAD You really have to like the sci-fi tank look to appreciate the design. Not enough front- or top-panel ports for all your VR accessories. The case interior is not as user-accessible as some.

THE BOTTOM LINE The big, bold Acer Predator G6 scores for VR performance, but it's not exactly the most sophisticated-looking desktop we've ever seen.

e Acer Predator desktop line has some of my favorite promotional copy of all time, at least when it comes to PCs. "Fight on the forefront of intergalactic gaming with a commanding advantage," the Predator's splash page says, promising that the system will "crush 4K gaming and prepare for virtual reality," while allowing you to "power-up for galactic domination."

It all fits in with the extreme design of this gaming desktop, which looks like the tank tread of some kind of future war machine. Or, as Acer describes it, an "intimidating armor-inspired design." Even the airflow vent directing air from the front to the back of the chassis is called an IceTunnel (as in, "Gaming is hot, so stay cool with IceTunnel cooling system").

Behind that somewhat goofy exterior and hyperbolic marketing-speak, is a set of components that we consider the sweet spot of first-gen VR desktops, with an Intel Core i7 6700K CPU and the Nvidia GeForce GTX 980 graphics card (but the just-announced GeForce 1080 card will probably eclipse that soon). This configuration also includes 16GB of RAM and a 2TB HDD/256GB SSD storage combo for a very reasonable $1,999. Different configurations are available internationally, starting at £1,299 in the UK. Only the smaller, newer Predator G1 tower is currently available in Australia, starting at AU$3,299.

While most of the VR-ready desktops we've tested and reviewed have plenty of ports on the front or top panels, the Predator G6 has only two USB 3.0 ports, a media card reader and headphone and mic jacks. Keep in mind your VR setup may require a couple of USB ports, plus one more for an Xbox gamepad (at least for the Oculus Rift), and you'll need ports for the included keyboard and mouse. Fortunately, there are four more USB 3.0 and two more USB 2.0 ports around the back. That in-the-box keyboard and mouse combo might be wired, but it's a nice, hefty SteelSeries set, one of the better pack-in accessory sets I've seen.

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Acer Predator G6 review:

THE GOOD The Acer Predator G6 fits our VR sweet-spot components into a big, distinctive case for under $2,000. Performance is great, basic software overclocking is built in, and there's a swappable drive bay in the front.

THE BAD You really have to like the sci-fi tank look to appreciate the design. Not enough front- or top-panel ports for all your VR accessories. The case interior is not as user-accessible as some.

THE BOTTOM LINE The big, bold Acer Predator G6 scores for VR performance, but it's not exactly the most sophisticated-looking desktop we've ever seen.

e Acer Predator desktop line has some of my favorite promotional copy of all time, at least when it comes to PCs. "Fight on the forefront of intergalactic gaming with a commanding advantage," the Predator's splash page says, promising that the system will "crush 4K gaming and prepare for virtual reality," while allowing you to "power-up for galactic domination."

It all fits in with the extreme design of this gaming desktop, which looks like the tank tread of some kind of future war machine. Or, as Acer describes it, an "intimidating armor-inspired design." Even the airflow vent directing air from the front to the back of the chassis is called an IceTunnel (as in, "Gaming is hot, so stay cool with IceTunnel cooling system").

Behind that somewhat goofy exterior and hyperbolic marketing-speak, is a set of components that we consider the sweet spot of first-gen VR desktops, with an Intel Core i7 6700K CPU and the Nvidia GeForce GTX 980 graphics card (but the just-announced GeForce 1080 card will probably eclipse that soon). This configuration also includes 16GB of RAM and a 2TB HDD/256GB SSD storage combo for a very reasonable $1,999. Different configurations are available internationally, starting at £1,299 in the UK. Only the smaller, newer Predator G1 tower is currently available in Australia, starting at AU$3,299.

While most of the VR-ready desktops we've tested and reviewed have plenty of ports on the front or top panels, the Predator G6 has only two USB 3.0 ports, a media card reader and headphone and mic jacks. Keep in mind your VR setup may require a couple of USB ports, plus one more for an Xbox gamepad (at least for the Oculus Rift), and you'll need ports for the included keyboard and mouse. Fortunately, there are four more USB 3.0 and two more USB 2.0 ports around the back. That in-the-box keyboard and mouse combo might be wired, but it's a nice, hefty SteelSeries set, one of the better pack-in accessory sets I've seen.

THE GOOD Apple upgrades the 21.5-inch iMac with a stunning 4K-resolution display, along with faster processors and Thunderbolt 2. The redesigned keyboard, mouse and trackpad all have rechargeable batteries and lightning connectors.

THE BAD The new processors are still one generation behind Intel's latest and there are no discrete graphics options. No HDMI input means it can't double as a TV monitor.

THE BOTTOM LINE The smallest Apple iMac trades up to a 4K display, and jumps to newer, but still not the latest, processors. While the design hasn't changed, newly crafted accessories with rechargeable batteries and Lightning connectors add flair and convenience.

Last year's addition to the 21.5-inch Apple iMac line caught our attention by cutting the starting price to $1,099 (£899 or AU$1,349) and positioning itself as essentially a MacBook Air recast as a desktop system; the new version for 2015 aims higher.

The flagship device in Apple's just-updated late-2015 iMac line is the configuration reviewed here, stepping up to a gorgeous 21.5-inch 4K resolution display and starting at $1,499 in the US (£1,199 or AU$2,099). Two other base models, at $1,099 and $1,299, retain their 1,920x1,080 displays.

It's worth noting that this is the more literal implementation of 4K in the new 21.5-inch iMac. The display resolution is 4,096 pixels wide, rather than the more common consumer version (sometimes called ultra-high definition or UHD), which has a just slightly lower resolution and is 3,840 pixels wide. That says to us that this system is targeting professional (and high-end enthusiast) photo and video users, who may shoot at that higher version of 4K resolution.

Your big, fancy 4K television set, and every other 4K computer we've seen to date, all adhere to the more consumer-targeted 3,840x2,160 version of 4K. The 4,096x2,304 on this new iMac screen will play any of your 4K content just fine, although the tiny difference in native resolution can have a small scaling effect, which we really only noticed when viewing 3,840-resolution test patterns.

The big secret about 4K is that a lot of people buy a 4K TV, monitor or computer, without really planning on viewing much 4K content on it. It's just the latest spec upgrade to strive for, and most of your video content, and even video games, aren't going past standard 1,920x1,080 high-definition anytime in the near future.

But higher-res screens such as the 4K display here have other advantages. As we saw with the5K display on last year's 27-inch iMac , individual pixels are practically invisible to the naked eye. On-screen text looks sharper and clearer than on lower-resolution screens, and Apple's expert scaling always keeps apps, menus and icons at a decent size, while giving you the option to mimic the look and feel of several different scaled resolutions. It's the same system Apple has used in all its Retina display models, going back to the MacBook Pro with Retina display.

But there's more to the new iMac than just a higher resolution. The new Retina display supports the wider P3 color gamut versus the more common sRGB (standard Red/Green/Blue) version. Translated for the rest of us, that means the display can show more of the green and red color spectrum (blue, the third leg of the color triangle, is already fairly maxed out under RGB). Apple says it adds up to 25 percent more available colors to display.

P3 is the standard for digital cinema projection in theaters, and for certain photo professionals and film and video experts, this is potentially a big deal. For photo hobbyists, you're unlikely to be able to appreciate the difference, as very little consumer-grade equipment is going to give you files that can take advantage of the wider P3 color gamut (some dSLR cameras, however, can). However, in side-by-side testing using some sample images, the effect was subtle but impressive, with richer reds and greens, and Apple's photo apps as well as third-party programs such as Photoshop, all support color far beyond standard sRBG.

It's little surprise that the new 21.5-inch Apple iMac looks the same as models from the past several years. The basic design language of the iMac has changed little since 2012, when it adopted the current setup of a slim, bowed screen sitting on top of an aluminum stand and minimalist base, a look that still manages to feel fresh years later.

But inside the familiar convex chassis of the iMac, there are some important spec changes for 2015. All three 21.5-inch models jump from Intel's fourth-generation Core i-series processors to newer fifth-generation chips. That's important because these iMacs were previously two generations of CPU behind. However, only the 27-inch iMacs, now all featuring the high-res 5K display, move up to the very latest CPUs, from Intel's recent sixth-generation of Core chips, sometimes known by the codename Skylake.

It's a shame the iMacs are still one chip generation behind, especially with nearly every consumer PC hitting stores this holiday season moving to Skylake chips. But, for a desktop system it's less important, as actual performance changes between generations of Intel chips are fairly modest. Most of the advantage comes in battery life, and for an all-in-one desktop, that's not going to be an issue.

Also new in the 21.5-inch iMac are Thunderbolt 2 ports for faster data transfer (if you have any Thunderbolt-equipped accessories) and some new hybrid hard drive options -- Apple calls them Fusion drives -- combining a small amount of solid-state memory for quick access of frequently used data, with a larger standard platter drive.

Besides the higher screen resolution and new CPUs, the biggest obvious change to the iMac line is the revamped collection of accessories bundled with it. The Apple wireless Keyboard, Magic Mouse and Magic Trackpad -- all familiar sights on Apple users' desks around the world -- have gotten their first overhaul in years, and it might be the new feature I'm most excited about.

All three lose their reliance on disposable batteries, instead moving to internal rechargeable lithium-ion batteries. That allows the keyboard and trackpad to slim down, removing the bulbus battery compartments that dominated the previous designs. The Magic Keyboard is smaller and flatter, but has slightly larger key faces. The Magic Trackpad 2 has a larger surface area -- it looks huge compared to the original version -- and now supports Force Touch, just like the pads in the MacBook and MacBook Pro. The Magic Mouse 2 looks the same, but is a hair lighter with better rubber tracks along the bottom.

Overall, this is an important update to the iMac line, as a better-than-HD display feels like table stakes these days for any premium laptop or desktop computer, and the improved color gamut support in the 4K and 5K displays will help keep the iMac line as a top choice for creative pros.

For everyone else, even if you don't regularly view 4K content, a sharp-looking Retina-level display is one of those things that's nearly impossible to give up once you get used to it, and the new 4K iMac is competitively priced with the handful of 4K-display Windows PCs we've reviewed.

If you have a model from the past few years, this isn't a must-have upgrade, but it may certainly be worth picking up the new keyboard and mouse or trackpad to give your older iMac a facelift.

Design and features

You can read any of our iMac reviews over the past three years to get a feel for the long-standing design of this high-end all-in-one. It still manages to look current, although some newer trends seen on the Windows side, from thinner bezels to touch screens, are absent here.

The iMac is dominated by its display, which also houses all the system components. It's still just 5mm thick at the edge, gently bowing out in the back. It looks almost paper-thin when viewed from the correct angle, and still pretty svelte even in full profile, where the rear panel bows out in the center into a gentle bowl shape.

That top section is connected via an adjustable hinge to a curved one-piece stand. If you're not connecting any external USB, Thunderbolt 2, or Mini-DisplayPort devices, and using Wi-Fi instead of a wired Ethernet connection, this is essentially a one-cable setup with a single white power cord in the lower middle of the back panel. As with most Apple computers, this is a sealed system, with no user-accessible components -- unlike the 27-inch iMac, which has an access port for the RAM slots.

Thinner, lighter accessories

The biggest physical change is in the new packed-in accessories, named the Magic Keyboard, Magic Mouse 2 and Magic Trackpad 2. As before, the keyboard and mouse are included by default, but you can choose to swap in the Trackpad instead of the mouse. With these new versions, however, the adding the Trackpad costs extra. All three are also sold separately, at $79 for the Magic Mouse 2, $99 for the Magic Keyboard and $129 for the Magic Trackpad 2 (all prices in US dollars). Previously, all three first-gem accessories were sold by Apple at $69 each.

That's a big jump in price for the trackpad, but it's easily the most impressive of the new accessories. The pad goes from aluminum-colored to off-white, and looks and feels massive. Apple says the surface area is 29 percent larger. Without the the cylindrical battery compartment, the pad has an even more minimalist look, lying flat on the tabletop with a slight wedge shape.

The Magic Trackpad 2 supports Force Touch, the new touchpad mechanic found in the MacBook and MacBook Pro laptops (a variant is also now in the iPhone and Apple Watch). Force Touch uses four corner sensors to replace the hinged "diving board" mechanism found in most touchpads, including Apple's previous ones.

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Apple iMac with 4K Retina display (21.5-inch, 2015) review:

THE GOOD Apple upgrades the 21.5-inch iMac with a stunning 4K-resolution display, along with faster processors and Thunderbolt 2. The redesigned keyboard, mouse and trackpad all have rechargeable batteries and lightning connectors.

THE BAD The new processors are still one generation behind Intel's latest and there are no discrete graphics options. No HDMI input means it can't double as a TV monitor.

THE BOTTOM LINE The smallest Apple iMac trades up to a 4K display, and jumps to newer, but still not the latest, processors. While the design hasn't changed, newly crafted accessories with rechargeable batteries and Lightning connectors add flair and convenience.

Last year's addition to the 21.5-inch Apple iMac line caught our attention by cutting the starting price to $1,099 (£899 or AU$1,349) and positioning itself as essentially a MacBook Air recast as a desktop system; the new version for 2015 aims higher.

The flagship device in Apple's just-updated late-2015 iMac line is the configuration reviewed here, stepping up to a gorgeous 21.5-inch 4K resolution display and starting at $1,499 in the US (£1,199 or AU$2,099). Two other base models, at $1,099 and $1,299, retain their 1,920x1,080 displays.

It's worth noting that this is the more literal implementation of 4K in the new 21.5-inch iMac. The display resolution is 4,096 pixels wide, rather than the more common consumer version (sometimes called ultra-high definition or UHD), which has a just slightly lower resolution and is 3,840 pixels wide. That says to us that this system is targeting professional (and high-end enthusiast) photo and video users, who may shoot at that higher version of 4K resolution.

Your big, fancy 4K television set, and every other 4K computer we've seen to date, all adhere to the more consumer-targeted 3,840x2,160 version of 4K. The 4,096x2,304 on this new iMac screen will play any of your 4K content just fine, although the tiny difference in native resolution can have a small scaling effect, which we really only noticed when viewing 3,840-resolution test patterns.

The big secret about 4K is that a lot of people buy a 4K TV, monitor or computer, without really planning on viewing much 4K content on it. It's just the latest spec upgrade to strive for, and most of your video content, and even video games, aren't going past standard 1,920x1,080 high-definition anytime in the near future.

But higher-res screens such as the 4K display here have other advantages. As we saw with the5K display on last year's 27-inch iMac , individual pixels are practically invisible to the naked eye. On-screen text looks sharper and clearer than on lower-resolution screens, and Apple's expert scaling always keeps apps, menus and icons at a decent size, while giving you the option to mimic the look and feel of several different scaled resolutions. It's the same system Apple has used in all its Retina display models, going back to the MacBook Pro with Retina display.

But there's more to the new iMac than just a higher resolution. The new Retina display supports the wider P3 color gamut versus the more common sRGB (standard Red/Green/Blue) version. Translated for the rest of us, that means the display can show more of the green and red color spectrum (blue, the third leg of the color triangle, is already fairly maxed out under RGB). Apple says it adds up to 25 percent more available colors to display.

P3 is the standard for digital cinema projection in theaters, and for certain photo professionals and film and video experts, this is potentially a big deal. For photo hobbyists, you're unlikely to be able to appreciate the difference, as very little consumer-grade equipment is going to give you files that can take advantage of the wider P3 color gamut (some dSLR cameras, however, can). However, in side-by-side testing using some sample images, the effect was subtle but impressive, with richer reds and greens, and Apple's photo apps as well as third-party programs such as Photoshop, all support color far beyond standard sRBG.

It's little surprise that the new 21.5-inch Apple iMac looks the same as models from the past several years. The basic design language of the iMac has changed little since 2012, when it adopted the current setup of a slim, bowed screen sitting on top of an aluminum stand and minimalist base, a look that still manages to feel fresh years later.

But inside the familiar convex chassis of the iMac, there are some important spec changes for 2015. All three 21.5-inch models jump from Intel's fourth-generation Core i-series processors to newer fifth-generation chips. That's important because these iMacs were previously two generations of CPU behind. However, only the 27-inch iMacs, now all featuring the high-res 5K display, move up to the very latest CPUs, from Intel's recent sixth-generation of Core chips, sometimes known by the codename Skylake.

It's a shame the iMacs are still one chip generation behind, especially with nearly every consumer PC hitting stores this holiday season moving to Skylake chips. But, for a desktop system it's less important, as actual performance changes between generations of Intel chips are fairly modest. Most of the advantage comes in battery life, and for an all-in-one desktop, that's not going to be an issue.

Also new in the 21.5-inch iMac are Thunderbolt 2 ports for faster data transfer (if you have any Thunderbolt-equipped accessories) and some new hybrid hard drive options -- Apple calls them Fusion drives -- combining a small amount of solid-state memory for quick access of frequently used data, with a larger standard platter drive.

Besides the higher screen resolution and new CPUs, the biggest obvious change to the iMac line is the revamped collection of accessories bundled with it. The Apple wireless Keyboard, Magic Mouse and Magic Trackpad -- all familiar sights on Apple users' desks around the world -- have gotten their first overhaul in years, and it might be the new feature I'm most excited about.

All three lose their reliance on disposable batteries, instead moving to internal rechargeable lithium-ion batteries. That allows the keyboard and trackpad to slim down, removing the bulbus battery compartments that dominated the previous designs. The Magic Keyboard is smaller and flatter, but has slightly larger key faces. The Magic Trackpad 2 has a larger surface area -- it looks huge compared to the original version -- and now supports Force Touch, just like the pads in the MacBook and MacBook Pro. The Magic Mouse 2 looks the same, but is a hair lighter with better rubber tracks along the bottom.

Overall, this is an important update to the iMac line, as a better-than-HD display feels like table stakes these days for any premium laptop or desktop computer, and the improved color gamut support in the 4K and 5K displays will help keep the iMac line as a top choice for creative pros.

For everyone else, even if you don't regularly view 4K content, a sharp-looking Retina-level display is one of those things that's nearly impossible to give up once you get used to it, and the new 4K iMac is competitively priced with the handful of 4K-display Windows PCs we've reviewed.

If you have a model from the past few years, this isn't a must-have upgrade, but it may certainly be worth picking up the new keyboard and mouse or trackpad to give your older iMac a facelift.

Design and features

You can read any of our iMac reviews over the past three years to get a feel for the long-standing design of this high-end all-in-one. It still manages to look current, although some newer trends seen on the Windows side, from thinner bezels to touch screens, are absent here.

The iMac is dominated by its display, which also houses all the system components. It's still just 5mm thick at the edge, gently bowing out in the back. It looks almost paper-thin when viewed from the correct angle, and still pretty svelte even in full profile, where the rear panel bows out in the center into a gentle bowl shape.

That top section is connected via an adjustable hinge to a curved one-piece stand. If you're not connecting any external USB, Thunderbolt 2, or Mini-DisplayPort devices, and using Wi-Fi instead of a wired Ethernet connection, this is essentially a one-cable setup with a single white power cord in the lower middle of the back panel. As with most Apple computers, this is a sealed system, with no user-accessible components -- unlike the 27-inch iMac, which has an access port for the RAM slots.

Thinner, lighter accessories

The biggest physical change is in the new packed-in accessories, named the Magic Keyboard, Magic Mouse 2 and Magic Trackpad 2. As before, the keyboard and mouse are included by default, but you can choose to swap in the Trackpad instead of the mouse. With these new versions, however, the adding the Trackpad costs extra. All three are also sold separately, at $79 for the Magic Mouse 2, $99 for the Magic Keyboard and $129 for the Magic Trackpad 2 (all prices in US dollars). Previously, all three first-gem accessories were sold by Apple at $69 each.

That's a big jump in price for the trackpad, but it's easily the most impressive of the new accessories. The pad goes from aluminum-colored to off-white, and looks and feels massive. Apple says the surface area is 29 percent larger. Without the the cylindrical battery compartment, the pad has an even more minimalist look, lying flat on the tabletop with a slight wedge shape.

The Magic Trackpad 2 supports Force Touch, the new touchpad mechanic found in the MacBook and MacBook Pro laptops (a variant is also now in the iPhone and Apple Watch). Force Touch uses four corner sensors to replace the hinged "diving board" mechanism found in most touchpads, including Apple's previous ones.