A Review of the Apple 21.5 inch iMac with 4K Retina Display

by on October 22, 2015
Performance at 4k

As we can pretty much expect of any Apple product and especially of any high-end Apple computing device, the 4K iMac is a fantastic performer on the whole. Its new single-fan cooling arrangement not only keeps the machine’s temperature lower than what was the case in older versions of the 21.5 inch iMac, it also has the machine running much more quietly overall, and this is saying a lot considering how generally quiet iMacs tend to be. The iMac’s new keyboard comes with a stiffer, hardier feel and has the same layout as that of the Retina Macbook from Apple and the accompanying trackpad of the 4K iMac comes with a Force Touch upgrade that improves overall working effectiveness. Furthermore, the Trackpad is clickable from edge to edge.

The new Intel Broadwell CPU technology and the GPU power of the 4K iMac are definitely designed to offer maximum smoothness as far as handling nearly any normal graphics you can throw at this machine goes and rendering 4K visuals, video and even gaming on the screen isn’t a problem for the 4K iMac in general.

On the other hand, what this iMac really excels at is the sheer scope of its 4K chops. The latest iMac is definitely features a display that’s definitely not your ordinary 4K UHD PC monitor with support for 3840 x 2160 pixels of graphics. Instead, here you get a maximum native resolution of what we could in effect call “super” 4K at 4096 x 2304 pixels and because the new El Capitan OS X has been built from the ground up to handle this heightened display resolution, scaling of all native Apple screen elements is superb, highly usable and very clean. Furthermore, the 4K iMac can scale downwards as needed with its Retina Scaling technology, allowing you to run the display at UHD resolutions of 2304 x 1296 pixels or a classic 1440´resolution of 2560 x 1440 pixels. In other words, the 4K iMac can be used to show the same amount of information as a 2048 x 1152 non-Retina screen, a 27 inch 1440p iMac or as a true 4K version of a typical 4K UHD monitor.

Finally, Apple uses the same custom timing controller from their 5K iMac to deliver full 4096 x 2304 resolution in this 4K iMac at a smooth 60Hz, which is a very useful feature for videos and gaming at UHD resolutions. We should also note that the 4K iMac can handle a single extra external screen at a 4K UHD resolution of 3840 x 2160 via its DisplayPort 1.2 cable, in addition to its native display. However, adding more screens than this won’t allow across the board 4K graphics. For this, we’ll have to wait until DisplayPort 1.3 becomes a thing in PC monitors.

The Good

The number of things to love about Apple’s new 4K iMac is more than extensive, whether you happen to be a dedicate Apple fan or not, either way, this cool, elegant new machine will impress you.

The 4K screen technology of the new iMac is nothing less than stunning. Colors on the display look fantastic and color spectrum coverage is excellent, with some finely detailed color saturation and vibrancy. While previous iMacs offered ample but somewhat basic sRGB coverage, the new 4K iMac supports the much more advanced digital cinema DCI-P3 color space that’s often used in movie theaters and it offers support for this color space to the tune of more than 99%, according to Apple. From what we’ve seen of how images on the screen look, we don’t have a hard time believing the manufacturer in this claim. Finally as far as the versatility of the 4K screen goes, as we’ve covered above, it’s very impressive and rather unique in the sense that it offers numerous resolution adjustments.

Finally we liked the inclusion of Thunderbolt 2 and the new rechargeable wireless peripheral essentials like the redesigned keyboard, trackpad and mouse for the 4K iMac.

The Bad

Of course, even Apple’s beautiful, elegant technology certainly isn’t perfect and the 4K iMac does suffer from its assorted flaws. None of them are what we’d at all called deal breakers but they do certainly reduce the lure of this otherwise wonderfully integrated and fluid piece of 4K computing machinery, especially considering the price Apple is asking for the machine.

Most glaring of all in the new iMac is its lack of HDMI connectivity options. Yes, the 4K iMac offers both DisplayPort 1.2 and Thunderbolt 2 connectivity options that do plenty for daisy chaining other 4K screens to the machine and also managing ultra HD gaming if you’re so inclined but the lack of even one single HDMI 2.0 port or at the very least an HDMI 1.4 port for 4K at 30 frames per second is a major omission on the part of Apple in our opinion. This laptop could serve as a very decent TV monitor with its truly stellar TV-like picture visual rendering technology and Apple decided not to give users the possibility of taking advantage of this.

Secondly, we also don’t much like the lack of powerful discrete graphics options in the iMac. Apple decided to give its 27 inch 5K iMac some of the best R9 graphics card power from AMD but in the 21.5 inch 4K the company only went with Intel’s default GPU hardware and in terms of graphics processing power, what you get here is only a bit better than the discrete Nvidia GeForce 750M GPU of last year’s 21.5 inch Retina iMacs, and that 750M card was itself already out of date for serious graphics processing even back then. In other words, for a 4K desktop with so much to offer in terms of beautiful visual specs, this iMac could have easily done better in this department.

Finally, we weren’t too happy with Apple’s decision to go with Intel’s Broadwell chip architecture. This chip technology is already one generation behind and here it is being installed in the company’s very latest piece of high-end desktop computing technology. Instead, Apple could have done here what they did with the 5K iMac and simply installed Intel’s brand new sixth generation Skylake chips, which are already shipping out with a number of other desktop and laptop machines on the market.


Type: Desktop PC computer
Screen size: 21.5 inches
Aspect ratio: 16:9
Resolution: 4096 x 2304
Included OS: Apple OS X El Capitan
Monitor Type: LED widescreen
Processor: Intel Core i5 i5-5675R 3.1 GHz processor
Storage (Hard drive): 1TB 5400 rpm SATA HDD
GPU (Video card): Intel Iris Pro 6200
Connectivity: WiFi, Bluetooth 4.0, Ethernet, 4 x USB 3.0 ports, 2 x mini-DisplayPort, 2 x Thunderbolt 2, 1 x SD card reader 1 x combo headphone/microphone jack, integrated speakers


The display of Apple’s new 21.5 inch 4K iMac is its real star attraction and the piece of the machines hardware that comes with the most impressive specs in our book. While Apple dropped the ball a bit on internal hardware specs in this machine, they really invested in some stunning visual capacity which sincerely impresses.

As we’ve already said, the 4K iMac is capable of handling a plethora of different resolutions depending on your needs and desires, and the internal OS X El Captitan operating system scales accordingly to handle all of them wonderfully. Since El Capitan was built with UHD compatibility baked right into it from the ground up, there should be no scaling problems to speak of with the iMac’s native software components or other Apple accessory software.

At a maximum native resolution of 4096 x 2304 pixels, the new iMac takes 4K to very new and highly uncommon levels of “True” 4K resolution which aren’t even found in the few other PC monitors on the market which do feature above-3840 X 2160 pixel resolution. The more usual True 4K spec is 4096 x 2160 and this iMac beats even that for a total of 9.4 million pixels on its screen, at a very robust pixel density of 217 ppi.

Finally, with Apple’s inclusion of the DCI-03 color space commonly used for digital cinema in movie theaters and other professional applications, the 4K iMac offers a much broader range of exquisite color shades, particularly for reds and greens, affecting the range and richness of tertiary colors like yellow, orange, magenta and cyan. In other words, the 4K iMac includes all the colors that make up the simpler sRGB spectrum and then takes them a whole lot further into pro territory. Apple is also using red-green phosphor LEDs to expand color gamut in its LCD screen.

The overall effect of all these extras means colors that really pop out with an exceptional level of realism and vibrancy. This color quality really complements the overall razor sharp detail on the screen in a beautiful way too, especially from the close distances at which you’re likely to be using the smaller display of the 21.5 inch 4K iMac.


Apple has always excelled at making deeply elegant minimalist electronics and the 4K iMac is an exceptional example of this design philosophy at work. This latest version of the iMac looks pretty much identical to last year’s models and if you’ve owned any of the models from the previous couple years or more, you know exactly what to expect in terms of visual appearance. Now while that may sound a bit boring and possibly is, the bottom line remains, Apple has made their 21.5 inch iMac into such a physically elegant machine that constant improvement isn’t really a necessity for the thing to stay very modern looking. With this machine, all major improvements are almost entirely internal and what’s on the outside looks great as it is.

As we’d already said, the main external design improvements involve a new, cooler, quieter single-fan setup that keeps the iMac humming along at a whisper and the range of external wireless peripherals which include a new redesigned Magic Keyboard, Magic Mouse 2 and Magic Trackpas 2. All of these peripherls are slightly more robust than their 2014 counterparts and all have independent rechargeable battery power.

Graphics, Hardware and Ports

As we’d already mentioned, the 2015 4K iMac actually lags a bit in terms of its graphics and processing hardware over what Apple could have done with such an otherwise powerful, snappy and fast piece of computing hardware. Yes, the new iMac runs wonderfully for any conventional use you can throw at it and will perform well even under heavier graphics loads but it can fold under pressure if really put to the kinds of tests that a full-blown 4K gaming PC would handle easily, or even if pushed to do things that the Apple 5K iMac and also manage without a problem. This is because the 4K iMac comes with no more than Intel’s stock Intel Core i5-5675R processor with Intel Iris Pro 6200 graphics processing technology to accompany it.

Neither of these are by any means bad processing systems but they also aren’t up to par with what the 5K iMac or a 4K gaming PC would offer. In basic terms, as far as graphics go, the 4K iMac is well designed for video editing and production work in 4K and wonderfully suited for photo editing tasks, particularly with is highly precise and broad color gamut coverage and contrast levels. However, for gaming in UHD resolutions, this machine doesn’t compare to superior 4K gaming-oriented computing systems or even to the 5K iMac.

The 1 TB HDD storage that comes native with the 4K iMac is also perfectly decent for getting started and runs quickly enough, but we would have liked a bit more kick than the 5400RPM of this rotating hard drive. In fact, we’d argue that Apple should move away from pure HDD technology and should have included a Fusion drive with both SSD and mechanical HDD technology in the 4K iMac –especially when you consider how tricky doing your own upgrades in an Apple machine like this can be.

Finally, the connectivity on the 4K iMac is reasonably good due to its inclusion of dual Thunderbolt 2 ports, 4 USB 3.0 ports and the inclusion of two mini DisplayPort connections. However, the omission of any sort of HDMI spec is annoying and prevents this iMac from being useful as a potential TV screen substitute for external media devices.

Software and Config

The 2015 4K iMac’s native OS is the new El Capitan OS X and we gotta say that we love its overall configuration and baked in ability to scale 4K graphics smoothly. At least as far as native Apple software in the new iMac goes, you won’t have the kinds of problems some Windows PC users with 4K display’s face with scaling issues. Furthermore, Apple has released the iMac with virtually no pointless bloatware that we noticed.

The new iMac can also have its configuration changed upward to replace the 8GB RAM with a 16GB version and the Intel Core i5 processor can also be upgraded to a considerably more powerful quad-core Intel Core i7 CPU.

Not so Great

To summarize very quickly, the following are the main things we didn’t like about the new 4K iMac:
• Lack of Intel’s most advanced Skylake processing chips
• No discrete GPU, the graphics integrate into the CPU
• Lack of HDMI connectivity
• The built-in HD storage memory could have been replaced by an HD/SSD fusion drive for such a new piece of Apple desktop hardware


The base retail price of the new 4K iMac from Apple is $1,499 with upgrades that add to this cost available from there.


• Superb color rendering with DCI-P3 color space
• Fast, powerful machine for most uses
• Beautiful design
• Wonderfully quiet, cool running
• Decent price tag
• 9.4 million pixels
• El Capitan OS X works great with 4K display


• No HDMI connectivity
• Uses slightly older Intel processing chip architecture
• No discrete Graphics card technology
• Storage memory could have been more advanced

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Bottom Line

While we consider Apple’s 5K Retina iMac to be the superior machine overall, the new 4k iMac has plenty going for it and comes at a relatively reasonable price for a piece of Apple technology with such a superb integrated True 4K display. On the whole, if you want to use this machine for photo editing, video editing and graphics design work, then it’s a great choice. As a 4K gaming computer on the other hand, the 4k 21.5 inch iMac isn’t much of a performer.

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