ASUS Zenfone 2 ZE551ML Review

ASUS launched the first ever smartphone/phablet which included a 4GB RAM on board. The company launched the device in India in April and dubbed it as their flagship device. However, it comes in three main variants, starting from Rs 12,999. Today, lets look at the ASUS Zenfone 2 ZE551ML Review.


The Zenfone series which included the Zenfone 4, 5 and 6 has been very popular in India, after its debut and was exclusively available on Flipkart. The naming scheme went for a toss when the next flagship was named Zenfone 2 and on top of that it came in three different main variants plus a couple of different variants with more storage. Thus, it creates a lot of confusion in a consumers mind and the officials at the helm of ASUS are to be blamed for it. We got the 4GB unit with 32GB built-in internal storage for review that is priced at Rs 19,999 on Flipkart. So, lets check out the ASUS Zenfone 2 ZE551ML Review.

ASUS Zenfone 2 ZE551ML Review: Hardware and Build Quality

Lets have a quick recap of the specifications. It comes with a 5.5-inch Full HD LED display, powered by a 2.3 GHz 64-bit Intel Atom Z3580 processor. It has a whopping 4GB of RAM with 32GB of internal memory, which can be further can expanded up to 64GB via microSD card. It has a 13 megapixel rear ‘Pixelmaster’ camera with an f/2.0 aperture and a 5 megapixel front-facing camera for taking selfies and video calling. It runs on Android 5.0 Lollipop with a heavy custom skin Zen UI on top of it. On the connectivity front, it comes with 4G LTE, 3G HSPA+, WiFi 802.11 a/b/g/n/ac (dual band), Bluetooth and GPS. The Zenfone 2 packs in a 3,000 mAh battery under the hood, which also comes with fast charging technology and charges 0-60% in around 39 minutes.

The Zenfone 2 is unapologetically fat with 10.9 mm body but has thin edges. Thus, it has a slightly curved slanting back which makes it easy to hold a 5.5-inch device and makes the design ergonomic too. The edges are so thin that ASUS could not place any buttons on either sides. This resulted in the power button being placed at the top middle, which is the most difficult to reach. To make things worse, it does not have much tactile feedback either. However, ‘Double tap’ gesture to wake and sleep works on the Zenfone 2, which ends up in never using the wake/sleep button, unless you want to power off or restart the device.

If we look at the front, there is a hearing grill at the top centre, couple of sensors and the 5 megapixel front-facing camera on the left. An ASUS branding below the grill followed by the 5.5-inch Full HD display. Below the display, we find three capacitive buttons which are not backlit but has silver paint job on them. At the bottom, we have the microUSB port and a microphone. There is a 3.5 mm audio jack, wake/sleep button and a secondary noise cancellation microphone on the top. Move on to the back and we have the dual-tone LED flash followed by the 13 megapixel Pixelmaster rear shooter and then comes the volume rocker. That is followed by the ASUS branding and at the bottom we find ‘Intel Inside’ logo and the big speaker grill. The concept of placing the volume rocker at the back is certainly inspired from the likes of LG.

ASUS Zenfone 2 ZE551ML: Photo Gallery

ASUS Zenfone 2 ZE551ML Review: Display

The Zenfone 2 ZE551ML rocks a 5.5-inch LED display with a resolution of 1920 x 1080 pixels (Full HD). It is protected by Corning Gorilla Glass 3 with oleophobic anti-fingerprint coating. It has a pixel density of 443ppi and gives out 400 nits of brightness. The display quality is quite good and the colour reproduction is soothing. The display is bright and it has good viewing angles as well. However, it does not perform well under direct sunlight. Colours do not pop out but you would enjoy consuming media on it.

ASUS Zenfone 2 ZE551ML Review: Performance and Gaming


The Zenfone 2 ZE551ML is powered by a 2.3 GHz 64-bit Intel Atom Z3580 processor, which is said to be up to 3.1 times faster than some of its quad-core competitors. On this chipset, the graphics performance is also promised to be up to 8.1 times quicker and it supports OpenGL 3.0. The 64-bit Intel chipset performs really well and is also capable of handling most things that are thrown at it. It is able to handle day-to-day usage without any throttling. We were able to browse sites with heavy graphical content, watch Full HD videos and high-resolution images, play high graphical intensive games without any struggle. The Zen UI based on Lollipop is smooth and there is no lag or frame drops when gliding through the UI. With the whopping 4GB of RAM on board, multitasking with 10-15 apps open seems to be a breeze. Whoever says “what will you do with 4GB RAM on your mobile?”, “it is a waste to have 4GB of RAM in a smartphone”, etc. No, it is really not. There is a big performance boost and with more power-hungry applications and OS, most flagships in 2016 will come with 4GB RAM. Out of the full RAM, 3.9GB is usable and about 2.6GB RAM is available for free when default apps are running in the background. The call quality was good.

We tried Asphalt 8, Mortal Kombat X, Modern Combat 5, Marvel Future Fight to test out the gaming performance of the Zenfone 2. With 4GB RAM on board, it is a beast and blazes through most of the games. There were no lag or frame drops to be honest. It is one of the best hand-held gaming device in the market and should be a smartphone gamers dream choice. The 5.5-inch Full HD display helps as well. The speaker quality was satisfying but not the best in this range.

ASUS Zenfone 2 ZE551ML Review: Camera

The best thing about the Zenfone 2 is that all the variants come with the same camera module. However, the camera is certainly a hit and a miss. It had the potential to be a great camera but we do not know if it’s the camera algorithm or the sensor itself, which made it an above average camera. The 13 megapixel Pixelmaster rear camera comes with a dual-tone LED flash and f/2.0 aperture. ASUS claims it to have “the world’s best HDR technology” and we seem to agree. We had the best result when we shot with the HDR mode. In low lighting or dimly light area or at a restaurant, it was difficult to focus and Low Lighting mode did not help either.

The camera UI on Zenfone 2 has many modes including Auto, Manual, HDR, Beautification, Super Resolution, Low Light, Night, Depth of Field, Effect, Selfie, GIF Animation, Panorama, Miniature, Time Rewind, PanoSphere, Smart Remove, All Smiles and Time Lapse. We have tried a couple of modes and HDR was the most impressive, as mentioned above.

Now, coming to the front-facing camera, there is a 5 megapixel shooter which packs in innovative features which includes a Beautification mode, that offers real-time image enhancement, skin softening and brightening, blush and colour correction, eye enhance and cheek thinning.

Check out the camera samples below. We have categorized it by camera modes.

Camera Samples: HDR

Camera Sample: Low Light (3MP)

Camera Sample: Auto & Other modes

Software, Battery Life and Connectivity

The Zenfone 2 runs on the latest Zen UI powered by Android Lollipop. It is a heavily customized UI which comes with a lot of in-house apps and bloatware. The number of pre-installed apps is too damn high in our opinion. Most of these apps are not used in real life scenario and are gimmicky in nature. However, Zen UI is smooth and the UI does not lag. It is very well optimized as well. We can add up to 7 home screens and there is customizable quick settings menu which comes with smart savings, reading mode, one hand operation, WiFi hotspot, Glove mode along with the usual quick settings toggle. We find default shortcuts in the first row, which are interchangeable or can be replaced.

The lockscreen has a quick access shortcut to launch the camera app, dialer and messages. You also get ‘One Hand Mode’ which reduces the screen’s size and makes it better to use the phone, if you have a smaller hand. As you already know about the ‘double tap’ to wake and sleep gesture mode and its the best gesture because of the power button placement. Other gestures are also there where we need to draw certain letters on the screen to open the apps in sleep mode. The Zen UI has some good features as well which are an absolute gem. We can pin the screen in the multitasking screen, which keeps the current screen in view until you unpin it. Pin lock can be used to lock the display in a single view. It also has Kids mode for app restriction. The colour saturation level can also be changed as it includes balance mode, reading mode, vivid mode and customized mode. If you select balance mode, you’ll get the most normal setting. On hitting reading mode, it increases the yellow tinge for better reading. Vivid mode pops up the colour and the customized mode can help you set your desired colour temperature, hue and saturation manually.


The phablet comes with a 3,000 mAh built-in Lithium Polymer battery that is equipped with fast charging capabilities. It charges from 0-60% in around 39 minutes which is impressive. All the variants support fast charging but the quick charger is not included in the lower variants. In our testing, we got over one day of battery life with moderate usage. It may not be the best in this class but has good battery life. If you use it heavily with 4G data on, it won’t last for a day.

The Zen UI throws in some useful power saving modes such as Customized mode, Optimized mode and Ultra-Saving mode. The app also shows the amount of battery used by the apps installed in the phone along with the most battery draining apps.

On the connectivity front, the Zenfone 2 has dual SIM support with 4G LTE. However, 4G can be used only on the first SIM and the second SIM can only be used for calls and SMS. You cannot use cellular data on the second SIM, be it even 2G or 3G and we feel that’s absolutely absurd. However, it is due to Dual Active SIM support, that we need to sacrifice cellular data on the second SIM. On the other hand, it comes with the usual WiFi 802.11 a/b/g/n/ac (dual band), Bluetooth 4.0, GPS, NFC and USB OTG. In this 32GB internal storage variant, about 25.53GB is usable. The memory can also be expanded up to 64GB using microSD card.

ASUS Zenfone 2 ZE551ML Review: Final Verdict

If you have gone through all the points in our AUS Zenfone 2 ZE551ML review, you’ll find the device to be one of the best in the affordable flagship or mid-range segment. Certainly, it is a crowded market with the likes of Xiaomi Mi 4 and the OnePlus One but Zenfone 2 is a force to be reckoned with. It has also launched in USA and Canada and has seen good overall demand. There is also a top of the tier variant with 128GB of internal storage which costs Rs 29,999. In case you can sacrifice on the RAM and display, the Zenfone 2 starts at Rs 12,999 on Flipkart in India.

So, if you want a raw powerhouse which can fulfil your computing needs, get the Zenfone 2 ZE551ML variant.

About the author

Bibek Saha

He is the Founder & Editor-in-Chief of The Techolic. A tech enthusiast who is always found reading or writing on technology. An avid Manchester United fan and a big time foodie. If not writing, he can be found watching the latest movies and TV shows. Interact with him on Twitter and Google+

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