Apple has made a big deal out of the increased brightness of the monitor -- 500 nits (candela per square meter) -- but our tests from 2014 show the "old" 5K tested almost that bright, at about 460 nits. (For comparison, most monitors top out around 400 nits.) This one is definitely brighter: it hit peak brightness of 540 nits in my tests. Still, most folks really don't want to use it at 100 percent: that's too bright. (For reference, in photo editing you usually work in the range of 120 to 220 nits.) A higher peak brightness does offer some extra longevity as brightness usually decreases over time. The important level Apple needs to hit next is 1,000 nits, which is in the .
The display still delivers excellent color accuracy, certainly the best I've seen in an all-in-one and possibly for monitors in its class in general, at least within the Adobe RGB and sRGB gamuts. Much has been made about the increase from an 8-bit per color palette -- referred to as "millions of colors" -- to 10 bits or "one billion" colors. That's not as big of a deal as it seems. Since it's only simulating 10 bits by fooling your eyes, the expansion doesn't help for color-critical, wide-gamut work, which requires a true 10-bit panel, among other things. It was already good enough for everything else.
(Just because a computer can do the math to generate a billion colors and a display can theoretically display any given one of them doesn't change the fact that humans can only differentiate about 7-10 million. The more colors it can display, though, makes it more likely you'll to be able to see differences between two close shades, especially in desaturated greens.)
And while games may look better thanks to the expanded color rendering and higher brightness, until High Sierra comes out with its generally more efficientgraphics software interface and optimizations, most speed-intensive gaming will remain a sub-optimal experience. And Macs aren't a key platform for most traditional PC games anyway. When new or noteworthy games do land on MacOS, they're often late, or offer much more limited graphics options.
As for performance, the combination of faster memory, processors and storage results in noticeably speedier operation. The Core i5 system acquits itself well for the essentials, such as streaming video, web browsing, email and so on, and Photoshop seemed pretty zippy working with medium (around 30MB) files. Given the results we've seen from the latest Core i7-based MacBook Pro, I think the Core i7 iMac model will be quite fast for an all-in-one.
A smart choice, but not a no-brainer
If you bought a 5K iMac in 2015 or 2016, there's no need to regret the timing; it will still support the new architectural features in MacOS High Sierra, such as a new file system, and even support for external graphics cards, as well as updated applications like Photos. As an upgrade from a small, slow 21.5-inch iMac or slower 27-inch, or moving from a MacBook, it's still an excellent choice that should last you more than a few years.
Alternatively, if you're looking for something beyond even the new CPU, GPU and memory options here, Apple's even higher-end iMac Pro is coming later this year, starting at $4,999 (roughly £3,845 or AU$6,715). Though if you're willing to spend that much and don't need workstation-certified components, you could also consider kitting out a top-end iMac 27 for about as much.
|Apple iMac 27 (2017)||Apple MacOS Sierra 10.12.5; 3.4GHz Intel Core i5-7500U; 8GB 2400MHz DDR4 SDRAM; 4GB Radeon Pro 570; 1TB Fusion Drive Journaled HFS+|
|Dell XPS 27 (early 2017)||Microsoft Windows 10 Home (64-bit); 3.4GHz Intel Core i7-6700; 16GB DDR4 SDRAM 2,400MHz; 4GB AMD Radeon R9 M470X; 512GB SSD|
|Dell XPS 27 (mid 2017)||Microsoft Windows 10 Home (64-bit); 3.6GHz Core i7-7700; 16GB DDR4 SDRAM 2,133Hz; 8GB AMD Radeon RX 570; 512GB PCIe SSD|
|HP Envy AIO 27 (late 2016)||Microsoft Windows 10 Home (64-bit); 2.8GHz Intel Core i7-6700T; 16GB DDR4 SDRAM 2,133MHz; 4GB Nvidia GeForce GTX 950M; 128GB SSD + 1TB HDD|
|HP Envy Curved All-in-One 34 (2017)||Microsoft Windows 10 Home (64-bit); 2.8GHz Intel Core i7-7700T; 16GB DDR4 SDRAM 2,133MHz; 4GB AMD Radeon RX460; 256GB SSD + 1TB HDD|
|Microsoft Surface Studio||Microsoft Windows 10 Pro (64-bit); 2.7GHz Intel Core i7-6820HQ, 32GB DDR4 SDRAM 2,133MHz, 4GB Nvidia GeForce GTX 980M; 2TB HDD + 128GB SSD|