Apple iMac with 5K Retina display (27-inch) review: Apple's 5K iMac impresses expert eyes (review)

Just when you thought it was safe to get comfortable with the look and language of 4K, Apple comes along and adds what the company is calling a 5K display in the premium 27-inch iMac all-in-one desktop.

Officially called the iMac with Retina 5K display, the screen uses a new material, oxide-based TFT, and borrowed tech from the Retina iPad to reduce pixel crosstalk to keep images sharp. The panel is also just as bright as the previous-gen model, but uses 30 percent less energy, according to Apple.

In person, that 5,120x2,880 display is simply stunning, especially when displaying high-res full-screen photos and video. The previous 27-inch iMac had a 2,560x,1440 display, making this 2x jump especially impressive. That 2013 model used an Nvidia GTX 775M graphics card, but for the 5K panel, Apple has switched (back to) AMD with the R9 290X. Apple has jumped between these two GPU brands before, and currently, you'll find AMD in the Mac Pro and new iMac, while Nvidia powers the 15-inch MacBook Pro and the non-5K iMac.

Gaming has never been a big deal on Macs, but that graphics-card muscle is vital for video editing and encoding, as well as CAD and design tasks, and that's one reason people choose a 15-inch MacBook Retina Pro, 27-inch iMac, or Mac Pro desktop, all of which include discrete graphics cards.

What you're not going to find here is the latest generation of internal components. Nvidia has new 900-series GPUs for both mobile and desktop, but as noted, AMD is the GPU of choice here. Intel has a new generation of CPUs coming soon, codenamed Broadwell, but those are not expected until early 2015 at the earliest.

In the meantime, you could hypothetically go with Intel's stopgap Haswell-E chips, just announced in August for high-end desktops, but here we've got a standard Haswell-generation Core i5 (with an i7 upgrade for an extra $250, £200, or AU$300).

If you've used any of the recent past generations of 27-inch iMacs, you already know what to expect physically. This is the same design, 5mm thick at the edge, gently bowing out in the back that looks so amazingly thin from the correct angle, and is frankly still pretty thin even in full profile.

This is the third year for this body shape, and the design has made it way all the way down to the base 21.5-inch iMac (or as we call it, the iMac Air). Still, it remains the sharpest-looking all-in-one you can buy, and the amazing 5K display will likely keep you so mesmerized you'll hardly notice anything else about the system.

Is this the iMac for you? If you're a photo or video professional, it's certainly worth a serious look. And, i you fall into that category, there's a good chance you're already eyeing a Mac Pro desktop, although this setup includes a built-in 5K display, and starts at $500 less. If you don't work with the ultra-high-resolution content, or don't sit with your nose inches from the screen, consider the standard non-5K 27-inch iMac, which starts at a more reasonable $1,800, £1,450, or AU$2,200.

Apple iMac with 5K Retina display (27-inch, 2014)

Price as reviewed	$2,499, £2,000, AU$3,000
Display size/resolution	27-inch, 5,120x2,880 screen
PC CPU	3.5GHz Intel Core i5 4690
PC Memory	16GB DDR3 SDRAM 1600MHz
Graphics	2GB AMD Radeon R9 M290X
Storage	1TB hybrid hard drive
Optical drive	None
Networking	802.11ac wireless, Bluetooth 4.0
Operating system	OS X Yosemite 10.10

Design and features

This is the same chassis as the most recent 27-inch iMac we reviewed, from late 2013. That design blew a lot of minds when first unveiled by Apple in October 2012, as artful photography and clever angles made the system look almost completely flat, although in person the rear panel bows out in the center into a gentle bowl shape.

As we noted of the 2013 iMac, the bowl-like panel and curved one-piece stand make this among the most organic-feeling of Apple's products. That's fitting, as the all-in-one is a desktop subgenre closely associated with family computer use, kitchen PCs, or creative/artistic work, which is a different feel than you get from a no-nonsense tower chassis or an on-the-go laptop.

The iMac still has a collection of rear-panel-only ports and, as with most Apple products, there's no easy user access to components -- except for the RAM, which is accessed via a small panel near the screen hinge. The included Apple Magic Mouse and keyboard are the same as previous models, and you can still swap out the mouse for the Magic Touchpad, my personal preference.

The 5K display, demystified

Let's talk about the real reason anyone is interested in this new iMac, the UHD-busting 5,120x2,880 resolution screen. Can you tell the difference between this and the previous model? Is it worth spending more for the new display? Did Apple skip 4K and go directly to 5K, just as Microsoft skipped Windows 9 in favor of Windows 10?

We dragged this new 2014 iMac with 5K Retina display into CNET's television testing lab, which is well-equipped for observing and testing displays from 1080p to 4K to, in this case, beyond. There, with the help and observational power of CNET's TV-testing expert David Katzmaier, we set the 5K iMac up next to a 2013 version, which has similar high-end specs (with Nvidia rather than AMD supplying the GPU), and a better-than-HD 2,560x1,440 resolution.

Note that, in this head-to-head, only the 2014 iMac had the latest OS update, codenamed Yosemite, and it's also worth acknowledging that the actual display on our 2013 iMac has been in service for a full year, although we saw no ill effects from that.

The first step was measuring the light output of each display when running a white test pattern, with both systems set to maximum screen brightness. The 2014 5K iMac rated 461.1 nits (cd/m2), while the 2013 version gave us 458.9 nits -- essentially the same light output.

Running through several professional test patterns from our arsenal of television testing files, a set of color bars looked completely identical on both displays, while a grayscale pattern was also nearly identical, but with just a hint of green on the 2014 5K iMac. A multiburst pattern, scaled up from its native 1,920x1,080 format, looked a bit softer on the 2013 iMac, its edges not as sharp or as well-defined.

Next, on full 4K resolution 3,840x2,160 resolution test pattern, neither system scaled perfectly. On the 2013 iMac, a bar within the pattern with a mutliburst pattern designed to display every other line looked almost entirely white, missing that part of the pattern entirely. On the 5K display, the lines appeared, but softly, without the sharpness one might find on a true 4K display, which would match the pattern pixel-for-pixel. On the 2013 iMac, close enough to the screen (less than about 12 inches), you can also see the pixel structure, which resembles a grid pattern.

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
Optical drive	None

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 Origin PC Millennium , 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.

Conclusion

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.

Handbrake Multimedia Multitasking test

Apple Mac Pro 109Apple iMac with 5K Retina display (27-inch, 2014) 155Dell XPS 27 157Apple iMac (27-inch, 2013) 195Lenovo Y50 Touch 210

Adobe Photoshop CS5 image-processing test

Apple iMac (27-inch, 2013) 175Apple iMac with 5K Retina display (27-inch, 2014) 177Lenovo Y50 Touch 180Dell XPS 27 180

Apple iTunes encoding test

Apple iMac with 5K Retina display (27-inch, 2014) 52Apple iMac (27-inch, 2013) 54Apple Mac Pro 54Dell XPS 27 83Lenovo Y50 Touch 90