ZenFone 2 (5.5-inch) review: Impressive low-light camera performance on this capable handset

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MSRP: $299.00

The Good The Asus ZenFone 2 delivers smooth performance, an impressive low-light camera, and has a clean feature-rich UI. The 5.5-inch screen is sharp and bright.

The Bad The phone has a cheap bulky feel and an unintuitive button layout. Its non-swappable battery delivers only decent life. The price is too high for its above-average capabilities.

The Bottom Line The Asus ZenFone 2 is too expensive for its above-average ability, but if the price agrees with you, the smooth performance and splendid low-light camera won't disappoint.

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7.0 Overall
  • Design 7
  • Features 7
  • Performance 8
  • Camera 7
  • Battery 6

If the 4GB version of the Asus Zenfone 2 were $100 cheaper, it would be near the top of our recommended phones list; however, its $299 and S$499 (converting directly to about £245 and AU$475) price makes it a tough sell in a world of capable sub-$200 phones.

There is a cheaper 2GB version of the phone retailing for $199 (converting to £127 and AU$249); however, since we've as of yet spent no time with the 2GB version, we can't yet say how it performs compared to the its 4GB sibling. Both versions of the phone are available now unlocked at Amazon, Newegg and Groupon in the US.

The 4GB ZenFone 2 is somewhere in-between budget and flagship, but unfortunately lacks the top-of-the-line performance and features we'd expect from a high-end handset. That said, it's capable in its own right, delivering silky smooth performance thanks to its combination Intel Atom CPU and 4GB of RAM. And while its 13-megapixel rear camera takes decent shots, its low-light performance handily beats that of the Samsung Galaxy S6 and Apple iPhone 6.

It has a sharp vibrant 5.5-inch screen, but the plastic build unfortunately feels cheap and bulky. Its Zen UI is clean, aesthetically pleasing and packed with useful features, but can at times isn't all that intuitive to navigate thanks to the changes Asus made to its Android 5.0 interface.

Those looking to spend less, should check out the Samsung Galaxy Grand Prime. It has longer battery life, decent cameras and costs less than $200. The Galaxy S6 and S6 Edge are the current highest of high-end Android, but tip the scales at $600 unless you're willing to commit to a 2-year contract.

Confusing lineup

What Asus calls the ZenFone 2 is actually two different models with five different variants, three with 5.5-inch screens and two with 5-inch displays. Each model has a different price point, RAM, and built-in storage capacity, but the whole range is marketed under the same name.

Asus is likely trying to avoid last year's problems with its first ZenFone line -- the phones were marketed as ZenFone 4, 5 and 6, which was probably even more confusing for consumers since it sounded like subsequent generations of phones were being sold at the same time. To lesson the confusion, we've created a table that lists the details of each of the new ZenFone 2 models. Our review unit is the 5.5-inch version with 4GB RAM and 32GB of onboard storage that retails for S$429 and $299 in the US (around £210 or AU$410).

Display Storage RAM Processor Price (US) Price (Singapore)
ZE551ML 5.5-inch (full-HD) 64GB 4GB Intel Atom Z3580 2.3GHz $299 S$499
ZE551ML 5.5-inch (full-HD) 32GB 4GB Intel Atom Z3580 2.3GHz NA S$429
ZE551ML 5.5-inch (full-HD) 32GB 2GB Intel Atom Z3560 1.8GHz $199 S$349
ZE550ML 5.5-inch (full-HD) 16GB 2GB Intel Atom Z3560 1.8GHz NA S$299
ZE500CL 5-inch (HD) 16GB 2GB Intel Atom Z2560 1.6GHz NA S$249


  • 5.5-inch, 1,920x1,080-pixel IPS (403ppi)
  • 6 x 3 x 0.4 inches (152.5 x 77.2 x 10.9 mm)
  • 6 ounces (170g)

The design of a modern smartphone is usually dictated by the screen size, and in this case the 5.5-inch full-HD display means the ZenFone 2 is quite a handful -- the phone checks in at 152.5 x 77.2 x 10.9 mm (6 by 3 by 0.43 inches) and isn't the thinnest of devices. It's just slightly shorter than the iPhone 6 Plus, but the Apple phone is thinner at 7.8mm. The thickness means the ZenFone does make its presence felt in the pocket, and with more smartphones taking the slim approach, the ZenFone 2's size and weight of 170g (6 ounces) doesn't do it any favors.

The phone's rear sports a brushed metal look, but it's actually plastic. Aloysius Low/CNET

Clad in plastic like the first ZenFone, the ZenFone 2 opts for a brushed metal look, unlike the soft-touch feel used previously. While it looks metallic, it still feels slightly plasticky (I prefer the original, though I can see why Asus chose to go with the metallic style) and it looks a lot more premium at first glance.

That said, the rear cover is replaceable and comes in a variety of colors -- the standard black and white, and a more colorful range of red, gold, grey. Asus will also sell a special range of "Illusion" covers that come in a pretty crystal pattern.

Viewed head on, the ZenFone 2 resembles the first ZenFone, from the Asus logo near the top speakers, to the concentric circle pattern below the 5.5-inch display. The touch-sensitive buttons are located just above that. In a way, I'm glad that Asus has stuck with the familiar, but I do wish the phone used software buttons instead -- this would probably have helped cut down on the phone's size.

The ZenFone 2 resembles the original ZenFone and uses touch-sensitive menu keys as well. Aloysius Low/CNET

Right at the top is where you'll find the awkwardly placed power button, and it's an odd choice, since Asus has chosen to borrow LG's great idea of moving the volume buttons to the rear of the phone. The button is quite a stretch to reach it if you're holding the phone with one hand. Asus should have just placed the power button on the rear, together with the volume controls.

The power button is placed at the top next to the 3.5mm audio jack. It's quite a strange position since you'll have to stretch your fingers to reach it. Aloysius Low/CNET

The removable rear cover gives you access to the dual-SIM and microSD slots. The 3,000mAh battery is non removable, so you won't be able to swap it out for a fresh one. Unlike some of the other dual-SIM phones which come with dual 4G capabilities, the ZenFone 2 only has one active 4G SIM, with the other SIM limited to 2G speeds.

Hardware and software features

  • 2.3GHz quad-core Intel Atom Z3580
  • 32GB of storage
  • 4GB of RAM
  • Expandable storage
  • 3,000mAh non-removable battery

Powered by Intel's Atom Quad Core Z3580 processor clocked at 2.3GHz, this model of the ZenFone 2 comes packing a whopping 4GB of RAM. Most smartphones, including high-end flagships, come loaded with 3GB at most. Asus claims having 4GB of RAM helps the ZenFone 2 multitask (more on this later), as multiple apps and can remain on standby in the background without needing to be offloaded to memory and reloaded.

Our review model came with 32GB of onboard storage, and if that somehow isn't enough for your needs, there's a microSD slot to add even more space. There's a 13-megapixel camera located at the rear, and a 5-megapixel shooter on the front.

The rear 13-megapixel camera comes paired with dual-LED flash. Aloysius Low/CNET
Inside you'll find the dual-SIM and microSD card slots. The battery is non-removable. Do also note the phone only supports 4G on one SIM slot, the other SIM slot is stuck on 2G. Aloysius Low/CNET

The 5.5-inch display comes with a full-HD resolution of 1,920x1,080-pixels, protected by Corning's Gorilla Glass 3. Sure, it's not a QHD display found on some flagships, but only a few users would be able to tell the difference between 2K resolution and full-HD. Also, the screen has wide viewing angles and colors are bright and vibrant. Even under direct sunlight, the integrity of the screen holds up well.

Asus has polished its Zen UI further, but it's a custom skin layered over Google's Android 5.0 Lollipop. Since its introduction last year, Zen UI features a flat minimalist look. Features from the earlier iteration return, such as Do It Later, a handy reminder app that helps you keep track of SMSes to reply to, articles to read and missed calls to return.

Zen UI packs plenty of new features, including the ability to theme the phone's look and icons. Screenshot by Aloysius Low/CNET
Zen UI also offers a lot of customization options that will boggle your mind with choice. Screenshot by Aloysius Low/CNET

Like Chinese smartphone maker Xiaomi's MIUI, Zen UI also features the ability to change your phone's theme, so if you don't like the current look, you can swap it to something you'd prefer. Another fun thing you can do is change the color of the fonts on your phone -- this works if you prefer a lighter background wallpaper -- you can then use a darker color for your fonts so that it shows up. New features include drawing on the screen when the phone is locked to activate features called ZenMotion and a guest mode for when you need to pass the phone over to a friend to use (though you'll need to make sure you password lock your phone first so they can't switch it back and access your data!).

The Auto-Start Manager app lets you select which apps to load into memory when you reboot your phone. You can also change the font colors on the home screens. Screenshot by Aloysius Low/CNET

There are also a bunch of hidden tweaks, such as the ability to double tap the Home button to turn on one-handed mode, and power users will appreciate the fact you can also set which apps will autorun when the phone boots to help it start faster.

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