ASUS ZenFone 2 ZE551ML (4GB RAM) - Great value from Singapore's first 4GB RAM smartphone

Overview

In 2014, ASUS launched the ZenFone series, a new range of Intel Atom-powered smartphones with value-based offerings, designed to compete against the likes of Xiaomi and Oppo. Last year, we saw the ZenFone 4, ZenFone 5, and ZenFone 6, and now ASUS has launched the ZenFone 2. Wait, what? If ASUS's naming conventions seem confusing (and they are), allow us to explain. 

The original ZenFone came in three screen sizes: 4-inch, 5-inch, and 6-inch (thus, 4, 5, 6). This year's ZenFone ditches the screen size naming and is so called simply because it's the second-generation ZenFone. What happens two years from now when ASUS gets onto the 4th generation ZenFone?

Even more confusingly, despite ditching the screen-size model names, this year's ZenFone is also available in different screen sizes: 5-inch and 5.5-inch. And the 5.5-inch model is available in both Full HD or 720p options.

But that's not all.

The 5.5-inch Full HD ZenFone 2 itself comes in two configurations, one with 2GB RAM and one with 4GB RAM and a speedier processor. And the 4GB RAM version also comes in two storage capacities, 32GB and 64GB (exclusive to Singtel).

Confused yet? Here's a table showing all of the ZenFone 2 variations:

Actually, if you just consider the ZenFone 2 as a family of phones, and start identifying them by individual product codes (ZE500CL etc.) it gets easier to identify which ZenFone 2 is which. Except, of course, for the top-end ZE551ML, where both the 2GB and 4GB RAM variants use the same product code. While you could purchase the right variant at the telco outlet by double checking and asking the right questions, we would advise you to shop carefully when making such purchases online.

All 2GB versions of the ZenFone 2 are immediately available, with the the 5-inch ZE500CL costing S$249, the 5.5-inch 720p ZE550ML costing S$299, and the ZE551ML costing S$349.

The 4GB variant of the ZE551ML will be released in Singapore on 16th May 2015, with a price tag of S$429 and S$499 for the 32GB and 64GB variants respectively.

With all of that out of the way, for this review, we'll be looking at the upcoming ZE551ML 4GB version (ours has 32GB storage), which ASUS has been calling it a "Monster Performance Smartphone." For simplicity's sake, from here on out, we'll just refer to it as as the ZenFone 2.

Design

The ZenFone 2 retains much of the design philosophy as its predecessor. The rear of the phone is ergonomically curved laterally (it's actually slightly more curved than last year's ZenFone) and fits comfortably into the palm of your hand, letting you keep a firm grip on it. While the phone is a bit heavier and thicker than many flagship phones these days, it's relatively compact and light for a mid-range handset, and still feels comfortable in hand. Size-wise, the 5.5-inch ZenFone 2 falls halfway between last year's ZenFone 5 and 6, which seems to have settled as the sweet spot for phablets, being large enough for enjoyable content consumption, and yet not too big to be awkward to operate one-handed. 

While the phone is still entirely plastic, ASUS has introduced a brushed metallic finish to the phone's removable back cover, which looks fairly convincing (at least at arm's length). It's probably not to everyone's taste, and 'metallic' plastic finishes always look pretty awful up close but, on the plus side, if you do hate it, ASUS has a whole range of optional back covers, ranging from multi-colored Transfusion covers to 3D-effect Illusion covers you can buy to pimp your phone (and you'll also find a number of other ZenFone 2 accessories over here). 

Removing the back cover reveals two micro-SIM slots and one microSD card slot (take note that the low-end 5-inch ZE500CL only has a single micro-SIM card slot). The ZenFone 2 supports Cat4 LTE, which provides data transfer rates up till 150 Mbps. However, unlike its predecessor, only one SIM card slot supports data transmission - the other slot is for calls only. The microSD card slot is located right above the micro-SIM slots, and supports cards of up till 64GB storage capacity. On our 32GB phone, after taking into account system files, there is a total of 25.53GB of total user space. It's worth noting that, despite the back cover being removable, the battery is not.

Like its predecessor, the ZenFone 2 has three capacitive navigation buttons below the screen. Unfortunately, also like its predecessor, these buttons remain unlit, which can make navigation in the dark difficult. Below the navigation buttons is a metallic accent with ASUS’s trademark concentric circle design, which is a nice premium touch.

The most noticeable change for the ZenFone 2 is that the volume rocker has been moved to the rear of the device. We've seen this button layout before on LG's phones, first with the G2, and continuing with its subsequent releases. On LG's phones, the power button is wedged in between the volume buttons, whereas on the ZenFone 2, the power button can be found on top.

The problem with this placement is that it makes the power button quite difficult to reach while using the phone one-handed. Having said that, ASUS has also incorporated a double-tap function on the screen to turn the display on/off (just like LG's KnockOn) feature, so you may never need to hit that awkward power button anyway.

As for the rest of the ports, the micro-USB port is on the bottom edge, while the headphone port is on the top, next to the power button, leaving both the left and right-side completely bare.

Display & Audio

This variant of the ZenFone 2 uses a 5.5-inch Full HD (1920 x 1080 pixels) resolution IPS LCD display, giving it a screen density of 403ppi. The screen is protected with Corning Gorilla Glass 3. Clarity is fairly good and color reproduction is accurate, although contrast could probably be a bit better. Viewing angles are excellent. 

Audio on the ZenFone 2 comes from a single speaker unit located on the back of the device. Sound output is rather average, and the rear-facing setup is less than ideal for any movie watching.

UI Features

The ZenFone 2 is powered by Android 5.0 Lollipop and runs on the latest version of ASUS' ZenUI. Most of the features from the previous version of ZenUI have been carried forward, which you can read about here: 5 notable features of the ASUS ZenUI

In addition, the ZenFone 2 gets some new features currently exclusive to it. ZenMotion lets you use gestures to quickly launch apps while the display is asleep. For example, draw a C to launch the camera, a W to launch the internet browser, an S to launch SMS messages, or an E to launch e-mail. ZenMotion also lets you flip the phone onto its front to mute an incoming call or any music playing.

SnapView is essentially a hidden user account where you can store anything you don't want prying eyes to see. You setup SnapView by creating a new lockscreen password. Whenever you unlock your phone using that password, you'll be in SnapView mode. Any pictures taken, or any apps installed or downloaded in SnapView mode will not be visible in Normal mode. Perfect for secret agents and anyone else leading shady double lives.

We've seen something similar on many phones now, but the ZenFone also includes a Kids Mode, which a parent can set up to limit the apps and functions the phone has access to, as well as the duration for which the kid can play.

View Cover Gestures

ASUS has also released a new range of View Covers for the ZenFone 2.

We saw these covers with last year's ZenFones as well, and they're back this year with some new and improved apps to increase their functionality:

• Weather View: See current weather conditions
• Camera Controls: Take photos without having to open your cover
• Music Controls: Play your music
• Flashlight: Turn on and off your camera flashlight
• Change Modes: change the phone modes to Airplane, Do Not Disturb, Vibrate, and Silent
• Check notifications
• Clock

Performance Benchmarks

There are three processor variants used in the various ZenFone 2 models:

• ZenFone 2 ZE500CL: Dual-core Intel Atom Z2560 1.6GHz processor 
• ZenFone 2 ZE550ML & ZE551ML (2GB): Quad-core Intel Atom Z3560 1.8GHz processor
• ZenFone 2 ZE551ML (4GB): Quad-core Intel Atom Z3580 2.3GHz processor

Since we're reviewing the top tier model, the Z3580 we'll be looking at is a 64-bit processor, which means it can utilize more memory than the maximum 3GB+ of previous 32-bit systems. In fact, the 4GB ZenFone 2 is the first smartphone available in Singapore with that RAM capacity.

In terms of performance, we expect this processor to be less powerful than today's top-end flagship phones running Qualcomm's Snapdragon 810, but more powerful than last year's Qualcomm Snapdragon 801.

Sunspider Javascript

SunSpider JavaScript helps measure the browsing performance of a device when processing JavaScript. It not only takes into consideration the underlying hardware performance, but also assesses how optimized a particular platform is at delivering a high-speed web browsing experience. The ZenFone 2 performed surprisingly well, surpassing the Snapdragon 801-equipped PadFone S, and even beating the 810-equipped LG G Flex 2.

Quadrant

Quadrant evaluates a device's CPU, memory, I/O and 3D graphics performances. The ZenFone 2 once again surpassed the Snapdragon 801-equipped Padfone S but this time fell quite far behind the 810-equipped LG G Flex 2. As expected, Samsung's Exynos 7420-equipped S6 is still way ahead of the pack in this benchmark.

3DMark (2013)

Originally developed as a PC benchmarking tool, 3DMark is now expanded to support multiple platforms including Android OS. The Ice Storm benchmark is designed for smartphones, mobile devices and ARM architecture computers.

For an in-depth understanding of 3DMark for Android, do head over to our article, "3DMark - Android Device GPU Performance Review." In a nutshell, it is an OpenGL ES 2.0 benchmark test that uses fixed off-screen rendering to run two graphics tests designed to stress the GPU performance of your device and a physics test to stress its CPU performance. The benchmark consists of three test portfolios:- Standard(720p resolution rendering), Extreme (1080p resolution rendering with higher quality textures and post-processing effects) and Unlimited (disabled v-sync, display scaling and other OS factors that make it ideal for chipset comparison).

Since all the recent flagship smartphones max out the scores for the Standard and Extreme tests, we will only be looking at the scores for Ice Storm Unlimited.

The ZenFone 2's PowerVR G6430 graphics engine was again surprisingly competitive, and was fairly close in performance to Samsung's S6 in this benchmark. If we were to compare these scores against the previous best from ASUS, the Zenfone 6, the results of the higher tier ZenFone 2 is significantly better.

Imaging Performance

The ZenFone 2 is equipped with a 13-megapixel rear camera sensor, with an aperture of f/2.0, as well as five-element lens. The camera also has a dual-color flash with one white and one warm LED, allowing for more accurate color tones when using flash. 

On the front, you'll find a 5-megapixel camera with an f/2.0 aperture and a 85-degree wide angle lens. The quality of the front-facing camera is pretty good, and the wide-angle lens is ideal for selfies.

The highlight of the camera of ZenFone 2 is its PixelMaster technology. First featured in the original ZenFone series, the PixelMaster technology has since improved by leaps and bounds. Starting from the ZenFone 2, the definition of PixelMaster has been broadened to include the suite of tools dedicated to the phone’s camera. In this section, we will look at how PixelMaster has improved over the past iteration.

Under day or room lighting, the quality of the photos are good, and generally matches or even surpasses the quality of most cameras on flagship phones. The only thing really missing is optical image stabilization.

Low-light performance

A carry-over from its predecessor, the ZenFone 2 can take good photos even in low light. In the case of extreme low light, a purpose specific low-light mode can be used, in which the PixelMaster technology can still render reasonably good photos, at the sacrifice of megapixel count (from 13MP reduced to 3MP). Here are some photos of night shots, both normal mode and with low-light mode turned on.

HDR Mode

Now a common feature in almost all smartphones, the HDR mode adjusts brightness and contrast in the foreground and background accordingly, resulting in even exposure across the whole image and thus ensuring both the foreground and background elements are clearly visible. For the ZenFone 2, the HDR balances the brightness well without any washed-out colors.

PixelMaster

Similar to Nokia’s PureView, PixelMaster can capture four 13MP photos in quick succession, and combine them to yield a photo that is effectively 52MP in resolution. However, the quality of Superpixel mode is rather poor, as can be seen in the photo.

Manual Mode

For those who want greater control in capturing photos, the ZenFone 2 includes a manual mode, where you can adjust focus, exposure, ISO, white balance and shutter speed.

Battery Life

All 5.5-inch ZenFone 2 models are armed with 3,000mAh capacity batteries, which is fairly standard for a phablet this size. The smaller 5-inch ZenFone 2 has a 2,000mAh battery. As mentioned previously, while the back cover is removable, the battery itself is not. 

Our standard battery test for mobile phones includes the following parameters:

• Looping a 800 x 480-pixel video with screen brightness and volume at 100%
• Wi-Fi and Bluetooth connectivity turned on
• Constant data streaming through email and Twitter

Battery life on the ZenFone 2 was slightly disappointing, and it only lasted just over seven hours in our video looping benchmark. As expected, power consumption was quite high. We suspect this is due to Intel's Atom Z3580 processor not being as power efficient as either Samsung's Exynos 7420 or Qualcomm's Snapdragon series.

One feature worth mentioning that is only available in the ZenFone 2 ZE551ML is ASUS' BoostMaster quick charging technology. ASUS claims that the BoostMaster can charge the ASUS ZenFone 2 from 0 to 60 percent within 39 minutes. In reality, it took us about 45 minutes before it reached the 60 percent mark. Interestingly, despite not using Qualcomm's QuickCharge technology, we discovered that the Samsung Fast Adaptive Charger works with the ASUS ZenFone 2. Going by that, we expect that any Qualcomm Quick Charger would work as well.

Portability

We measure the portability of a device by calculating its battery life to (weight x volume) ratio. Due to its underwhelming battery life and fairly large size, the ZenFone 2 was by far the worst contender in this category.

Conclusion

Based on the top-end variant of the ASUS ZenFone 2, we can confidently say that ASUS has once again proven that low-cost devices can easily challenge their most expensive competitors in several aspects.

Our review unit costs just S$429, which is a bargain considering its near to flagship-level benchmark performance, Full HD 5.5-inch display, reasonably good camera and comfortable ergonomics. Its full plastic design isn't the most attractive, but at this price level we're not complaining, and some of the optional back cover designs do look quite premium. It's also rare to find quick charging in a smartphone at this price level.

If you're not too concerned with having the best build out there, and you can live with its slightly underwhelming battery life, the ZenFone 2 is an excellent choice for anyone on a budget. Oh and don't forget that you can accessorize it with a lot of useful add-on items.

Once again, readers should take note that this review only covers the ZE551ML 4GB RAM variant of the ZenFone 2. This version with 32GB and 64GB capacity options will be available from 16th May. Meanwhile, we've also notified ASUS of our interest to also review the currently available lower cost variants, so stay tuned for future comparisons.

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