But the real test is how each iMac would perform with 4K video. We ran an excellent native 4K video clip, created by Florian Friedrich of UHDcontent.eu, on both machines side by side and under the same conditions we use to test television displays.
For the most part, our 4K video test files looked identical in terms of quality and sharpness on both screens, at least at first. On closer examination, leaning in just inches from each, we found visible differences between the two displays. For example, on a scene with fine branches passing in front of a tree, the 5K display showed finer detail among the delicate branches, while the 2013 display lost some of that detail in favor of harder edges, akin to turning off anti-aliasing on a video game.
Up close, a patch of white water rolling through a creek clearly showed the display's pixel grid on the 2013 version, similar to our test pattern. No matter how close we got, no pixels were visible on the 5K Retina display.
From our hands-on, and eyes-on, testing, it's clear that there is a measurable difference between the 5K Retina display on this year's iMac, and the 2,560x1,440 display on the previous (and still available) model. That point made, is it enough of a difference that you should spend more on the higher-resolution model?
If you're editing the highest-resolution photographs possible, and sitting close enough to the screen to see its pixel grid, then yes, there's a good case to be made. The same goes for video editors who work at 4K resolution, especially if you see this iMac as a more cost-effective substitute for last year's 4K-friendly Mac Pro desktop.
But for the majority of mainstream consumers, you're unlikely to even notice the difference, unless you have an expert guide, such as Katzmaier, to point the details out to you.
Apple iMac with 5K Retina display (27-inch)
|Video||Mini DisplayPort/Thunderbolt 2 (x2)|
|Audio||Stereo speakers, combo headphone/microphone jack|
|Data||4 USB 3.0, SD card reader|
|Networking||Ethernet, 802.11ac Wi-Fi, Bluetooth|
Connections and performance
In a single row on the back of the display chassis, you'll find four USB 3.0 ports, two Thunderbolt/Mini-DisplayPort connections, an SD card slot, Ethernet jack, and headphone plug. That's the same lineup as on last year's 27-inch iMac, and the same you'll find on the non-5K 27-inch iMac Apple still sells.
The default Radeon R9 290X with 2GB of GDDR5 memory can be upgraded to an AMD Radeon R9 M295X with 4GB of GDDR5 memory for an additional $250, £200, or AU$300.
Storage options in the new iMac with 5K Retina display start with a 1TB Fusion Drive or a 256GB solid-state drive for the same price, but can be configured with a 3TB Fusion Drive (for an additional $150, £120, AU$190), or 512GB ($300, £240, AU$560) or 1TB ($800, £640, AU$960) SSDs. Memory starts at 8GB with two sticks of 4GB, though with four slots total, you can opt to pay Apple for 16GB ($200, £160, AU$240) or 32GB ($600, £480, AU$720).
As the new AMD R9 graphics card is the only internal hardware change from the 2013 iMac, you can rightly expect essentially the same performance, and the 2013 and 2014 iMacs were nearly perfectly matched. The high-end Mac Pro was significantly faster in our multitasking test, but that system uses professional-grade Intel Xeon processors.
If you're thinking of trying some 5K gaming, you may want to temper your expectations. First, the Mac gaming library remains small, especially when it comes to new releases. And, even ones that are available, including a few of our favorites such as BioShock Infinite and Metro: Last Light, are often ports with limited functionality and graphics options.
Second, pushing a game at higher-than-1080 resolutions is difficult for most systems, as we've found from our 4K gaming tests on Windows systems. You'll either need an extremely powerful PC, such as the recently reviewed, or you'll need to dial the visual quality settings way back.
We tested the most recent Tomb Raider game on the 5K iMac, and found that at high detail settings at the native 5K resolution, the game ran at 12.8 frames per second. Dialing the detail settings down to low at the same resolution, we got 19.2 frames per second -- closer, but still not a very playable experience. We tried changing the game's resolution to 1,920x1,080, reset the details to high, and got 59.2 frames per second, showing that more than quadrupling the resolution takes a huge toll on game performance.
Like the Mac Pro, the new iMac with 5K Retina display is a highly specialized product, not intended for everyday mainstream computing. One might even call it the iMac Pro, and for casual web surfing, social media, and even gaming, the less-expensive non-Retina version will do just fine.
But, having experienced the 5K screen up close, it's also hard to un-see the effect of never being able to detect the pixel grid on the screen. I've had several photo and video professionals tell me this is exactly what they're looking for, and at only $500, £400, or AU$550 more than the closest comparable non-5K 27-inch iMac, it's the equivalent of adding the cheapest possible aftermarket 4K display. If you're in that professional or semi-pro category, the math may just work out for you on this.