Asus Zenfone 2 ZE551ML review: Premium experience under affordable price

Smartphones are growing from low-end to high-end segments and are getting bigger as well as smarter each day. While leading smartphone vendors such as Samsung and HTC are in a race to offer a greater premium experience, some Asian players like Asus are on a move to make the same experience available even under an affordable price bracket. After launching the Zenfone series last year, the Taiwanese company brought the Zenfone 2 range at the Consumer Electronic Show (CES) 2015 to continue offer an affordable yet decent smartphone experience. Though the initially announcement suggested that it is launching just a single new smartphone model as a successor to its highly popular Zenfones, Asus launched a whole new range of four Zenfone 2 models in India diversify its offering. The range includes the entry-level ZE550ML and the high-end ZE551ML models. Moreover, the most high-end Zenfone 2 model is claimed to be the world’s first 4GB RAM featuring smartphone. We got the Zenfone 2 ZE551ML 4GB RAM model at our labs soon after its India launch. So here is our in-depth review.

Asus Zenfone 2

What’s in the Box

The Asus Zenfone 2 ZE551ML comes with a price tag of Rs. 22,999. This is the price tag at which companies like Samsung and HTC are willing to offer a mid-range experience but interestingly, Asus has planned something different. And one can see that difference right from the box of the Zenfone 2. It does not have anything that makes it a box of a mid-range smartphone.

Asus has designed the box of the Zenfone 2 on the same aesthetics that it used for designing the box of the first-generation Zenfone smartphones. Thus, there is the Zenfone 2 branding and the smartphone image right on top of the box and there is the same color tone that the smartphone model has. This means that if you are going for a grey-color Zenfone 2, like ours, then you’ll get to know about that right from color tone on the box.

Asus Zenfone 2 with in-box content

Once unboxed, the box of the Zenfone 2 ZE551ML shows the smartphone unit on top and underneath, it has an AC charger, USB-to-microUSB data cable, warranty card and a user guide. The AC charger that the company has provided inside the box supports quick charging at 9V.

Watch Asus Zenfone 2 unboxing video:


Similar to the first-generation Zenfone series, the entire range of the Zenfone 2 is designed with a whole-plastic built. The built does not provide any flimsy feel in hand and seems to be quite premium from first glance.

The front side of the Zenfone 2 ZE551ML has a large display panel that has a Corning Gorilla Glass 3 protection. Below the display panel, there are three touch-sensitive controls for back, home and recent apps and there is a chin that debut on the predecessor. Top side of the display has Asus branding, earpiece, secondary camera sensor and a couple of sensors – ambient light sensor and proximity sensor. Additionally, there is a multi-color notification LED light to notify users on new calls, text messages and emails.

Asus Zenfone 2 with Corning Gorilla Glass 3 protection on front

Asus has not provided any control or port on the left and right sides of the Zenfone 2. This helps in reducing the thickness and makes the overall built slimmer than the first-generation Zenfone.

The bottom side of the Zenfone 2 has a microUSB port and a pinhole microphone.

Asus Zenfone 2 with microUSB port and primary microphone on bottom

On top, there is a secondary microphone, power/lock key and a 3.5mm jack. The power/lock key has steel finish to enhance looks of the smartphone.

Asus Zenfone 2 with secondary microphone, power/lock key and 3.5mm jack on top

Turning the Zenfone 2 towards rear shows a premium back cover that has faux brushed steel finish. The steel finish on the back cover gives the same look that generally available on some HTC One flagships. Furthermore, there is a volume rocker that reminds us some of the recent smartphones by LG. The rear side lastly features a primary camera sensor along with dual-tone (dual-LED) flash.

Asus Zenfone 2 with faux brushed steel back cover and volume rocker on rear

The back cover of the Zenfone 2 is removable and there are two SIM card slots and a microSD card slot under it. The cover also has an NFC chip that enables Near Field Communication technology on the smartphone. It is worth noting here that despite of the removable back cover, the battery pack on the smartphone cannot be removed and is embedded under the chassis.

Asus Zenfone 2 with two SIM card slots and a microSD card slot under back cover

Overall, the design of the Zenfone 2 ZE551ML is a mix-and-match of the first-generation Zenfone series as well as some high-end smartphones by LG and HTC. The smartphone has 152.5 x 77.2 x 10.9 mm dimensions and is 170 grams in weight.



Asus brought its PixelMaster technology on the first-generation Zenfone smartphones that was widely praised by reviewers and users all across the globe. The Zenfone 2 continues the same experience using the same technology and has some additional improvements to deliver even better results.

The Zenfone 2 ZE551ML sports a 13-megapixel camera sensor on the rear along with dual-tone (dual-LED) flash. The camera has an f/2.0 aperture lens and comes equipped with Optical Image Stabilisation (OIS) technology to offer sharper results. In addition, there is a 5-megapixel camera sensor on the front to let users take selfies and their self portraits as well as do video calling using some VoIP services.

Asus Zenfone 2 with 13-megapixel rear camera

Asus has provided a list of features on the software front to enable decent camera performance on the Zenfone 2 ZE551ML. There is a proprietary camera app which has an array of shooting modes such as Night, Panorama and HDR. Furthermore, users can use Beautification, Super Resolution or Low Light to get more from the smartphone’s camera. A special Selfie mode and GIF Animation mode are also available to provide some advance imaging options.

For professionals and serious photographers, the Zenfone 2 ZE551ML has Smart Remove mode and comes along with a Manual mode. The Manual mode particularly has settings for adjusting White Balance, Exposure Value, ISO and Focus. Besides, there is Depth of Field mode to let users create bokeh effect in their frames especially while capturing macro shots.

Asus Zenfone 2 camera interface

We tested camera performance of the Zenfone 2 ZE551ML by taking a variety of shots under different environment and some of them are available below for reference. Throughout our testing, we noticed that both the camera sensors of the smartphone are designed to compete against other smartphones in the same segment. Although features such as HDR mode and manual settings are not as impressive as on some high-end smartphones, there is no lag in capturing images under any lighting environment. Color production, noise levels and white balance of the camera sensors under Auto mode also offer a new crisp in each shot.

Asus Zenfone 2 ZE551ML camera samples

Apart from capturing still images, the Zenfone 2 ZE551ML is capable of recording videos in up to 1080p (full-HD) resolution. The camera app has video stabilisation to reduce the amount of jerks in final footage and there is Time Lapse mode to capture time-lapse shots at an interval of up to five seconds. In addition, the smartphone provides options to adjust white balance and exposure value while recording videos.

We have not found any issue while recording videos with the Zenfone 2 ZE551ML. Moreover, both the camera sensors deliver impressive video recording results.

Overall, the Asus Zenfone 2 ZE551ML can be considered among the best camera smartphones under mid-range segment. The proprietary features enhance the image results and deliver a professional-like experience to novices.



We have already seen the design aspects and camera performance of the Zenfone 2 ZE551ML in the previous sections. And now, it’s time to dig further to bring out all its major pros and cons.

The Asus Zenfone 2 ZE551ML features a 5.5-inch IPS display with 1,920 x 1,080 pixels (full-HD) resolution that makes 403ppi pixel density. The display delivers a fair amount of brightness in indoors as well as outdoors but it does not give impressive results under direct sunlight. Asus has provided a Corning Gorilla Glass 3 on top of the display that protects from minor scratches but prone to smudges. Besides, there are some software tweaks like Asus Splendid app and Reading mode to enhance viewing experience on the Zenfone 2.

Asus Zenfone 2 ZE551ML

Asus has given Android 5.0 Lollipop operating system on the Zenfone 2 ZE551ML with its Zen UI on top. In addition, the smartphone has options to receive future updates as well.

Asus Zenfone 2 ZE551ML with Android Lollipop operating system

The proprietary Zen UI interface on the Zenfone 2 ZE551ML has many tweaks that one wants in stock Android. There is a tap-to-unlock feature that unlocks the lockscreen by double tapping the screen. Users can also lock the screen by double tapping on the homescreen. The interface has also a wide list of customisations, including the ability to choose fonts, wallpapers, themes, scroll effects and icon packs. There is a notification panel on top of the screen with Quick Setting toggles and a brightness adjuster. Users can create new homescreens or delete any of the existing screens. Furthermore, there is an option to add widgets and shortcuts as well as create folders on the homescreens.

Asus Zenfone 2 ZE551ML with Zen UI on top of Android Lollipop

Apart from some major customisations and homescreens, Zen UI on the Zenfone 2 ZE551ML has a proprietary app drawer which has apps and widgets tabs and unique features such as smart group, lock apps and hide apps. Users can create folders in the app drawer and can adjust the sorting of the app icons through a view mode.

Asus Zenfone 2 ZE551ML with proprietary app drawer

Similar to the first-generation Zenfone smartphones, the Zenfone 2 has some pre-installed apps. These apps include Clean Master, 50+ games, TripAdvisor, Dr. Safety, Amazon Kindle and Zinio among others. Thankfully, users have the option to easily uninstall any of the pre-installed apps to make their smartphone more personalised.

On the part of telephony and messaging, the Zenfone 2 has a smart dialler and messaging app and comes preloaded with Asus Keyboard. The smartphone has dual-SIM card support with dual-standby technology. The company has additionally provided call recording to let users record their telephonic conversations. Furthermore, there is 4G LTE support on Indian as well as international networks. We have not found any issue while making calls or sending text messages on the Zenfone 2. In-call quality was also fair during our tests.

Asus Zenfone 2 ZE551ML with smart telephony and messaging support

The Zenfone 2 ZE551ML has pre-installed File Manager app that allows users to take a look at the internal storage of the smartphone. The app also works with external storage devices as the smartphone has USB On-the-Go (USB OTG) support.

For browsing the Web, the Zenfone 2 ZE551ML has pre-installed Browser and Google Chrome web browsers. Both the web browsers support multi-tabbing and there is HTML5, CSS and JavaScript. The large-size display enables a decent web browsing experience and high-end hardware makes that experience buttery smooth.

The Zenfone 2 ZE551ML has pre-installed Google Play Music and Play Movies and TV apps as well as Asus Gallery and Music. All these apps are designed to support most of the widely used audio and video formats. The built-in loudspeaker delivers decent audio quality and there is Asus AudioWizard app to let users select any of the preset modes, namely Smart mode, Music mode, Movie mode, Recording mode, Gaming mode and Speech mode. However, the position of the loudspeaker makes audio muffle when the smartphone is kept on a flat surface or on a mattress.

To test performance of the Zenfone 2 ZE551ML on benchmark apps, we installed some of the popular apps. These apps include AnTuTu, Geekbench, NenaMark, Quadrant Standard Edition, Real Pi Benchmark and Vellamo. On AnTuTu Benchmark version 5.7, the smartphone resulted 43,266 and on Geekbench version 3.3.2, it resulted 905 single-core score and 2,773 multi-core score. When tested on NenaMark 2, it resulted 59.7fps frame rate and on Quadrant Standard Edition version 2.1.1, it got 23,257 overall scores. It took 7.84 seconds elapsed time on calculating the unit of Pi through Real Pi Benchmark, while Vellamo version 3.1 resulted 1,202 overall scores.

Asus Zenfone 2 ZE551ML performance on benchmark apps

Apart from testing its performance through benchmark apps, we use played some popular games on the Zenfone 2 ZE551ML. These games include Asphalt 8: Airborne, Brothers in Arm 3, Modern Combat 5: Blackout and Need for Speed: Most Wanted. There was no lag in terms of graphics or processing throughout our playtime on the smartphone. However, we noticed some heat from the rear, but this was bearable and is quite a common issue in most of the mid-range smartphones.

In terms of hardware, the Zenfone 2 ZE551ML has an Intel Atom Z3580 chipset that has a quad-core 2.3GHz CPU, PowerVR Rogue G6430 GPU and 4GB of RAM. There is up to 128GB on-board storage along with a microSD card slot for further expansion up to 128GB. We got the 32GB variant that has over 25GB internal storage for end users. The smartphone has Wi-Fi 802.11 a/b/g/n/ac, Bluetooth 4.0, A-GPS and a microUSB port and there is built-in NFC support. Asus has provided an array of sensors that mainly include an accelerometer, ambient light sensor, proximity sensor, magnetic field sensor and a gyroscope.

The Zenfone 2 ZE551ML packs a 3,000mAh Lithium-Polymer battery that has quick charging support. The battery has enough juice to deliver over a day backup on a single charge. On the downside, it cannot be replaced from the user end and generates some amount of heat while charging.




Asus Zenfone 2 ZE551ML


The Asus Zenfone 2 ZE551ML not only has a new built and a refreshed list of specifications over the first-generation Zenfones but it also offers the same high-end performance that one today gets from a premium flagship. In short, this new smartphone has a potential to lead the mid-range price segment.

Turn to the next page to know about the key specifications of the Asus Zenfone 2 ZE551ML.


ModelAsus Zenfone 2 ZE551ML
Display5.5" IPS display
Resolution1920 x 1080 pixels
Memory128GB storage, expandable up to 128GB via microSD card
OSAndroid 5.0 Lollipop OS
Camera13MP AF primary camera with LED flash, 5MP secondary camera
VideoYes, Full-HD (1080p) @ up to 30fps
SensorsAccelerometer, Ambient Light, Gyroscope, Proximity sensor, Magnetometer
ChipsetIntel Atom Z3580
CPU2.3GHz quad-core CPU
GPUPowerVR Rogue G6430 GPU
ConnectivityBluetooth 4.0, Wi-Fi 802.11 a/b/g/n/ac, A-GPS, NFC, MicroUSB (USB OTG)
BatteryLi-Po 3,000mAh
Dimensions152.5 x 77.2 x 10.9 mm
Weight170 g