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iMac 21.5-inch 4K (2017) Review



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Trusted Reviews Recommended


  • Stunning screen
  • Powerful processor
  • Near-silent running
  • Good graphics performance
  • Excellent peripherals


  • Needs an SSD
  • Measly 8GB of RAM

Key Specifications

  • Review Price: £1449.00
  • 21.5-inch 4096 x 2304 P3 display
  • 3.4-3.8GHz Intel Core i5-7500 (upgradable to Core i7)
  • 8GB DDR4 memory (upgradable to 32GB)
  • 1TB Fusion drive (upgradable to SSD)
  • 4GB AMD Radeon Pro 560 GPU
  • Magic Keyboard and Magic Mouse 2 included
  • VESA-mountable option available
  • 4 x USB 3.0, 2 x ThunderBolt 3/USB-C 3.1, Gigabit Ethernet, SDXC card reader, 3.5mm headset jack
  • MacOS Sierra

What is the 21.5-inch iMac?

The 4K 21.5-inch 2017 iMac is a refresh of Apple’s iconic all-in-one. It comes stacked with the latest processor and graphics options, alongside the same butter-smooth Apple experience you’ve come to expect.

If you’re after a powerful and good-looking all-in-one, you really don’t need to look much further.

21.5-inch iMac – Design and build

If you’ve seen an iMac in the past decade, then you’ll have a pretty good idea of what this latest model will offer. Despite its age, the iMac still offers up great-looking design with its combination of silver aluminium, tapered edges and simple, single-footed stand.

The iMac is a thoroughly modern device when it comes to connectivity. There are four USB 3 ports, a further two high-speed Thunderbolt 3 ports that can handle data at up to 40Gbps – perfect for high-end storage peripherals and monitors – and an SDXC card slot, Gigabit Ethernet and headphone jack.

Related: Best desktops and all-in-one PCs
iMac 2017

All great, all welcome – but mostly in the wrong place. Even before Apple’s decision to taper the edges of the iMac to almost nothing, the company always chose to place ports on the rear of the system, out of sight. While I make no great objection to most of the ports being placed back there, a single USB port alongside a 3.5mm jack on the right or left-hand edge of the all-in-one would have been most welcome.

For easier access to your hot-swapping peripherals you’ll need to buy a dock. It’s at least easy to swing the iMac around on its foot to gain access to the rear – but it isn’t exactly seamless.

Related: 27-inch iMac review

Also, be sure to budget in a bit more if you want to hook up a non-Thunderbolt monitor to your iMac; you’ll need an adapter for VGA, DVI, and HDMI, or a Thunderbolt 3-to-DisplayPort cable for more modern screens.

21.5-inch iMac – Keyboard and mouse

Apple ships its 21.5-inch iMac with the Magic Keyboard and Magic Mouse 2 (both wireless) as standard, and both peripherals are excellent. The Magic Keyboard is similar to every other Mac keyboard you may have cast your eyes upon. It sports an aluminium body with white keys and grey lettering, and a top row of function keys that modify screen brightness, control media playback and volume, while also helping you to navigate the desktop with Mission Control and the app menu. There’s also an eject button for the non-existent DVD drive.

iMac 2017

Key travel is short, but short travel is fine if the keypress action is responsive – and in my opinion it’s just about enough. Your fingers can dance across the keyboard with relative ease, and there’s no mushiness whatsoever. I’d have personally preferred a desktop version of the Butterfly keys that Apple uses in its latest MacBooks, but these do the job without issue. The standard keyboard that comes in the box doesn’t have a numberpad, and you’ll pay a cool £30 for the privilege of upgrading to one. But this also nets you larger arrow keys and Page Up and Page Down keys.

The Magic Mouse 2 is excellent, and essential if you want to get the most out of macOS’s gesture-centric design. Upon setting up your iMac, you’ll want to increase the mouse’s movement sensitivity, because it’s hilariously sluggish by default. From there, it moves smoothly across a standard desk and I didn’t experience any range or cut-out problems. The top surface has both a physical click and a touch-sensitive layer, which means you can perform regular clicks and use one- and two-fingered gestures to navigate the OS.

Magic Mouse 2

Essential gestures include single-finger scrolling, two-fingered desktop switching and a two-fingered tap for setting up Mission Control just how you like it. Some curious gestures are disabled by default, including single-finger page navigation (going back a web page), and alternative clicks are also disabled by default.

You don’t get the full complement of gestures that you’d find on a trackpad; you can replace the Magic Mouse 2 with the Magic Touchpad instead for £50 extra.

21.5-inch iMac – Screen

The 21.5-inch iMac’s 4096 x 2304 screen is one of its big talking points – and the panel supplied here by LG is a fine example. My calibration equipment measured 100% of the sRGB colour gamut, 86% of the Adobe gamut and 98.6% of the DCI-P3 gamut. Images shot in RAW will benefit massively, with details that would otherwise be invisible on an inferior screen positively leaping out on the iMac panel.

Related: Colour gamuts explained

It tops out at a significant 532 nits of brightness. This is probably too bright for most people, but manages relatively – if not class-leading – deep blacks measuring in at 0.47 nits. This equates to an overall contrast figure of 1115:1.

Perhaps the only complaint one can have about this screen is its size. 21.5 inches is manageable, but in a world where 24-inch business monitors are the norm, it can feel slightly cramped. This problem isn’t quite so bad thanks to macOS’s excellent Mission Control system, which makes it easy to swipe between desktops, but those who are used to bigger desktops will definitely feel the pinch.

21.5-inch iMac – Audio and webcam

Audio-wise, the iMac is a powerhouse. The stereo speakers sit behind the screen and manage some super-impressive performances with both music and cinematic content, and are probably the best speakers you’ll find on any desktop PC.

The webcam and microphone, meanwhile, are decent as well. The webcam produces natural images, while the microphone is clear enough for both Siri and folk to understand easily.

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