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Apple iMac with 4K Retina display (21.5-inch, 2015) review: Apple packs more pixels into its smallest iMac

A deeper dive into how Force Touch works and what it can do can be found here. The sensors allow you to click anywhere on the pad's surface with identical results, and the Force Click effect, which combines the sensors with haptic (or taptic) feedback, allow you to have two levels of perceived clicking within an app or task. It can be used to bring up context-sensitive content when you use the firmer, double-level click on files or individual words, from pop-up previews to dictionary definitions to Apple Maps directions.

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The Magic Keyboard also loses the cylindrical battery compartment, and now sits flat on your desk as well. The overall footprint is 13 percent smaller according to Apple, the key faces themselves are slightly larger and have a new scissor mechanism under each key. The top row of function keys has graduated to full-size from the half-height keys on the previous Apple keyboard. In hands-on use, typing feels very similar to the older keyboard, and also similar to typing on any Mac keyboard, save for the wide, shallow keys of the 12-inch MacBook.

The Magic Mouse 2 is the least changed of the three accessories. Its body remains the same, but the rubber runners on the bottom panel have been tweaked for smoother gliding over your table or mousepad. The minimalist design has its fans, but it's never been my favorite mouse, and for years I've recommended swapping it out for the trackpad. It's a shame the Magic Trackpad 2 costs more now. I'd still choose it over the mouse, but die-hard mouse fans may disagree -- as they very vocally have when I suggested the mouse era was over or that touchpads were naturally superior, even for desktops.

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All three rechargeable accessories connect and charge to one of the iMac's USB ports via a standard Lightning cable, and a full charge should last a month or more, according to Apple. Connecting via Lightning also pairs the accessory with the system, so you don't have to search for it though the Bluetooth menu. These will also pair and work with existing Macs that have Bluetooth 4.0.

4K, with a professional twist

You can easily add the new keyboard, trackpad or mouse to your current iMac. The real selling point here is that this is the first 21.5-inch iMac with a 4K display. At 4,096x2,304 native resolution, it contains 9.4 million pixels, which is more than four times the number of pixels in a standard 1080p HD display (Apple's 27-inch 5K iMac has 14.7 million pixels).

As with all of Apple's Retina-class displays (the name Apple uses for its better-than-HD displays across laptops and desktops), the real difference comes when you use one for a while and then go back to a lower-resolution display. You're suddenly aware of individual pixels, and how on all of Apple's Retina screens they're essentially small enough and numerous enough to be invisible. The same basic point goes for the handful of 4K or nearly 4K laptop screens we've seen on Windows systems, including the upcoming Microsoft Surface Book (which has a 3,000x2,000 resolution).

For working on 4K video, that means you can preview your work full screen at full resolution. For photo editors, it means more pixels on the screen at once, instead of endless zooming and navigating. For casual Web surfers, it means even basic black text on the white background looks crisper and clearer, which may mean less long-term eye strain.

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With the help of CNET TV and video expert David Katzmaier, I loaded up a series of 4K videos and test patterns. The 4K videos, mostly scenes of natural landscapes or picturesque architecture, looked great, to no surprise. The IPS (in-plane switching) panel also made sure the images looked crisp and didn't fade when viewed from side angles. Katzmaier's expert eye, however, did note that there was a slight scaling effect going on when viewed inches from the display. And he was right -- nearly all the 4K consumer-level footage you're likely to find is at the more common 3,840x2,160 UHD resolution, and when viewed full screen, some scaling needs to happen. We confirmed this by firing up a 3,840x2,160 test pattern and saw the same scaling we observed in last year's 5K iMac.

But unless you spend a lot of time staring at 4K test patterns, it's a largely academic issue. Nearly all of the content you're likely to view on this system, from games to online video, will be upscaled from 1,920x1,080, and still look fantastic and pixel-free. That's especially important on a display that will likely be only a foot or so from your face, as opposed to a 10-foot 4K TV experience, where the benefits of 4K are more dubious.

Yes, you can still save a few hundred dollars and get the older 1,920x1,080 display, but from our phones to our televisions to our tablets, shoppers are acclimating to higher resolutions, and moving up to this great-looking 4K display provides a certain measure of future-proofing.

Ports and connections

Video mini-DisplayPort/Thunderbolt (x2)
Audio Combo headphone/microphone jack
Data 4 USB 3.0, SD card reader
Networking Ethernet, 802.11ac Wi-Fi, Bluetooth 4.0
Optical drive None

Connections and performance

In a single row on the back of the chassis is a collection of ports and connections, including four USB 3.0 ports, two Thunderbolt/mini-DisplayPort connections, an SD card slot, Ethernet jack and a headphone plug. The only real difference this year is that the Thunderbolt ports have been upgraded from the original Thunderbolt spec to the newer Thunderbolt 2. Missing is USB-C, the small, reversible plug found in the 12-inch MacBook and a handful of Windows PCs. Between this and the new Beats Pill+ speaker, it certainly seems as if Apple is betting big on Lightning as its default connector, rather than USB-C.

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With the new 4K iMac, you're stepping up from Intel's fourth-generation Core i5 and Core i7 processors to the fifth generation. In codename terms, that's going from Haswell to Broadwell. But, that's still one step away from the chips just starting to ship in consumer laptops and desktops this fall, the sixth generation of Intel's Core chips (yes they also have a codename, Skylake). Those brand-new 2015 processors are found in the more advanced 27-inch iMac models, but the 21-inch systems are a full generation behind.

That may not do much for your bragging rights to having the most updated computer on the block, but it's also not something that's going to have a huge impact on day to day use for most people. The big secret of the computer biz is that processors from even a few generations ago are perfectly fine for the work most of us put our systems through. There's been a huge shift over the past several years towards cloud-based tools that run in a Web browser, from Web-based email to online productivity suites such as Google Docs and Microsoft's online Office apps. Beyond that, we spend a lot of time on social media and online media streaming, all of which are considered rather lightweight tasks.

The real benefit, year over year, of having the latest Intel processors, is improved power-efficiency and better battery life, which are more important for laptops and hybrids than for desktops.

In our CNET Labs benchmarks, this new 4K iMac with a 3.1GHz Intel Core i5-5675R CPU performed on par with other recent Core i5 systems, showing the minimal performance jump between generations of Intel chips in the everyday tasks we use to test. It was about as fast as last year's big 27-inch 5K iMac, although no doubt the new Skylake-powered 27-inch models would be faster. Bringing up the rear is the latest Apple laptop, the 12-inch MacBook, which runs a rarely used Intel chip called the Core M that has, so far, underwhelmed in the handful of systems we've seen it in.

In hands-on use, the new iMac felt very zippy, even when playing back 4K video files, manipulating large photo files, or jumping between multiple browsers and multimedia apps.

While the 27-inch systems offer discrete R9 graphics from AMD, the 21-inch models now only include Intel's default graphics hardware. Last year's higher-end 21-inch iMacs included Nvidia GeForce 750M graphics, but that was already a well out-of-date graphics chip a year ago (the current equivalent would be the GeForce 950M -- for mainstream gaming we'd suggest at least a 960M GPU).

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So while you can play back and even edit 4K video on the new iMac, a gaming machine this is not. In a casual gaming test, we ran Tomb Raider at 1,920x1,080 resolution and medium graphics settings and saw a playable 30.3 frames per second. Just for the sake of curiosity, we ran the same game at the full 4K resolution, and it scored a mere 6.7 frames per second.

Conclusion

The pitch for this revamped Apple iMac is pretty simple: Take last year's high-end base configuration, upgrade it to a 4K display and newer (although not the newest) processors, while keeping the price the same. Adding to the appeal are the newly redesigned included accessories, Thunderbolt 2 and more hybrid hard drive options. The lower-cost base model 21-inch iMacs get most of the same refinements, minus the new display. One letdown is that the very basic Nvidia graphics card from the previous $1,499 configuration has been removed.

If you have a relatively recent iMac, and aren't heavily invested in 4K video editing or super-high-resolution photography, there's not a compelling reason to upgrade. Refreshing your keyboard and mouse or touchpad would be very tempting, but those new accessories are also sold separately. If you're a true power user, you're probably already leaning toward a 27-inch iMac (especially now that the entire line has 5K Retina displays) or even a Mac Pro desktop.

But if you're looking for a mid-range all-in-one with high-end feel, and one of the best-looking displays we've seen, the 4K upgrade is worth a little extra investment, and should age well over the next few years, especially as we move further and further into the 4K era.

Handbrake Multimedia Multitasking test

Apple MacBook Pro (15.6-inch, 2015)
149
Apple iMac with 4K Retina display (21.5-inch, 2015)
153
Apple iMac with 5K Retina display (27-inch, 2014)
155
Toshiba Satellite P50t-BST2N01
181
Apple MacBook (12-inch, 2015)
465
Apple iMac (21.5-inch, 2014)
466

Note:

Shorter bars indicate better performance (in seconds)

Adobe Photoshop CS5 image-processing test

Apple iMac with 4K Retina display (21.5-inch, 2015)
170
Apple iMac with 5K Retina display (27-inch, 2014)
177
Apple MacBook Pro (15.6-inch, 2015)
190
Toshiba Satellite P50t-BST2N01
197
Apple iMac (21.5-inch, 2014)
270
Apple MacBook (12-inch, 2015)
307

Note:

Shorter bars indicate better performance (in seconds)

Apple iTunes encoding test

Apple iMac with 5K Retina display (27-inch, 2014)
52
Apple iMac with 4K Retina display (21.5-inch, 2015)
57
Apple iMac (21-inch, 2014)
78
Toshiba Satellite P50t-BST2N01
90
Apple MacBook Pro (15.6-inch, 2015)
97
Apple MacBook (12-inch, 2015)
130

Note:

Shorter bars indicate better performance (in seconds)

System Configurations

Apple iMac with 4K Retina display (21.5-inch, 2015) Apple OS X 10.11 El Capitan; 3.1GHz Intel Core i5-5675R; 8GB DD3 SDRAM 1866MHz; 1536MB (shared) Intel Iris Pro Graphics 6200; 1TB HDD
Apple iMac (21-inch, 2014) Apple OS X 10.9.3 Mavericks; 1.4GHz Intel Core i54260U; 8GB 1,600MHz DDR3 SDRAM; 1792MB (shared) Intel HD Graphics 5000; 500GB HDD
Apple iMac with 5K Retina display (27-inch, 2014) Apple OS X 10.10 Yosemite; 3.5GHz Intel Core i5-4690; 8GB 1600MHz DDR3 SDRAM; 2GB AMD Radeon R9 M290X; 1TB Fusion HDD
Apple MacBook Pro (15.6-inch, 2015) Apple OS X 10.10.3 Yosemite; 2.5GHz Intel Core i7-4870HQ; 16GB DDR3 SDRAM 1600MHz; 2GB AMD Radeon R9 M370X; 512GB SSD
Apple MacBook (12-inch, 2015) Apple OS X 10.10.2 Yosemite; 1.1GHz Intel Core M-5Y31; 8GB DDR3 SDRAM 1600MHz; 1536MB Intel HD Graphics 5300; 256GB SSD
Toshiba Satellite P50t-BST2N01 Microsoft Windows 8.1 (64-bit); 2.4GHz Intel Core i7-4700HQ; 16GB DDR3 SDRAM 1600MHz; 2048MB (dedicated) AMD R9 M265X; 1TB Hybrid HDD

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