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ASUS ZenFone 5 review: Budget X

By James Lu - 3 Jul 2018
Launch SRP: S$488

Benchmark Performance, Imaging, Battery life, and Conclusion

Benchmark Performance

The ZenFone 5 is powered by a mid-range Qualcomm Snapdragon 636 processor with 4GB RAM. This is actually a downgrade from last year's ZenFone 4, which used a 660 processor, but it's also why the ZenFone 5 is a lot more affordable.

There aren't that many phones using Qualcomm's 636 processor - the most notable being Xiaomi's Redmi Note 5 Pro, which unfortunately we don't have on hand - so we'll be comparing the ZenFone 5 to other mid-range processors including the 625-powered Redmi 5 Plus, and 660-powered Oppo R11s. We've also included the Snapdragon 835-powered Xiaomi Mi MIX 2, which is now available for S$590, just S$102 more than the ZenFone 5.

  ASUS ZenFone 5 (2018) ASUS ZenFone 4 (2017) Oppo R11s Xiaomi Redmi 5 Plus Xiaomi Mi MIX 2
  ASUS ZenFone 5 (2018) ASUS ZenFone 4 (2017) Oppo R11s Xiaomi Redmi 5 Plus Xiaomi Mi MIX 2
Launch SRP
  • From S$488
  • From S$698
  • From S$699
  • From S$299
  • From S$699
Operating system
  • Android 8.0 Oreo with ZenUI 5.0
  • Android 7.1 Nougat with ZenUI 4.0
  • Android 7.1 Nougat with Color OS 3.2
  • MIUI 9.5 based on Android 7.1.2
  • Android 7.1.1 (Nougat) with MIUI 8
  • Qualcomm Snapdragon 636 Octa-core (8 x Kryo 260)
  • Qualcomm Snapdragon 660 Octa-core (4x2.2 GHz Kryo 260 & 4x1.8 GHz Kryo 260)
  • Qualcomm Snapdragon 660 Octa-core (4x2.2 GHz Kryo 260 & 4x1.8 GHz Kryo 260)
  • Qualcomm Snapdragon 625 octa-core 2.0GHz Cortex-A53
  • Qualcomm Snapdragon 835
Built-in Memory
  • 4GB RAM
  • 6GB RAM
  • 4GB RAM
  • 4GB RAM (Singapore variant)
  • 6GB RAM
  • 6.2-inch / 2,246 x 1,080 pixels (402 ppi) / 18.7:9 aspect ratio / IPS LCD
  • 5.5-inch / 1,920 x 1,080 pixels (401 ppi) / 18:9 aspect ratio / Super IPS+ LCD
  • 6.01-inch / 2,160 x 1,080 pixels (401 ppi) / 18:9 aspect ratio / AMOLED
  • 5.99-inch, 18:9 aspect ratio / IPS / 2,160 x 1,080 pixels
  • 5.99-inch / 2,160 x 1,080 pixels (402 ppi) / IPS
  • Rear: 12-megapixel f/1.8 with 4-axis OIS + wide-angle 8-megapixel f/2.0
  • Front: 8-megapixel f/2.0
  • Rear: 12-megapixel f/1.8 with OIS, + 8-megapixel
  • Front: 8-megapixel f/2.0
  • Rear: 16-megapixel f/1.7 + 20-megapixel f/1.7, 2x optical zoom
  • Front: 20-megapixel, f/2.0
  • - Rear: 12-megapixel (f/2.2, 1.25 μm), phase detection autofocus, dual-LED dual-tone flash
  • - Front: 5-megapixel
  • Rear: 12-megapixel, f/2.0, PDAF, two-tone flash, 4-axis OIS, 1.25µm pixel size
  • Front: 5-megapixel
  • Wi-Fi 802.11 a/b/g/n/ac, dual-band, WiFi Direct, hotspot, Bluetooth 5.0, A2DP, LE, EDR, GPS, GLONASS, NFC
  • Wi-Fi 802.11 a/b/g/n/ac, dual-band, WiFi Direct, hotspot, Bluetooth 5.0, A2DP, LE, EDR, GPS, GLONASS, NFC
  • Wi-Fi 802.11 a/b/g/n/ac, dual-band, WiFi Direct, hotspot, Bluetooth 4.2, A2DP, LE, EDR, GPS, GLONASS
  • Wi-Fi a/b/g/n, Bluetooth 4.2 LE, GPS, AGPS, GLONASS and Beidou positioning, FM radio, IR blaster, micro-USB 2.0
  • Wi-Fi 802.11 a/b/g/n/ac (dual band), Bluetooth 5.0, NFC, Wi-Fi Direct, Wi-Fi Display, USB Type-C 2.0
Storage Type
  • 64GB internal storage
  • Expandable up to 256GB (via microSD shared with SIM 2 slot)
  • 64GB internal storage
  • Expandable up to 256GB (via microSD shared with SIM 2 slot)
  • 64GB internal storage
  • Expandable up to 256GB (via microSD shared with SIM 2 slot)
  • 64GB internal storage (Singapore variant)
  • microSD support up to 128GB
  • 256GB internal storage
  • 3,300mAh
  • 3,300mAh
  • 3,200mAh
  • 4,000mAh
  • 3,400mAh
  • Qualcomm Quick Charge 3.0
  • 153 x 75.7 x 7.9 mm
  • 155.4 x 75.2 x 7.7 mm
  • 155.1 x 75.5 x 7.1 mm
  • 159 x 76 x 8.1mm
  • 150.5 x 74.6 x 7.7 mm
  • 155g
  • 165g
  • 153g
  • 180g
  • 187g

N.B. The ZenFone 5 has a feature called AI Boost. The phone will ask you if you want to turn it on anytime you start a game or benchmark, as well as a few other compute-intensive apps. You can toggle it on/off yourself from the Quick Settings menu by tapping the rocket ship icon. When turned on, you'll be warned that "AI Boost may slightly affect battery usage time."

For the following benchmarks, the light green bar is with AI Boost off, while the dark green bar is with AI Boost on.

SunSpider Javascript

SunSpider JavaScript measures 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 in delivering a high-speed web browsing experience. 

The ZenFone 5's 636 processor fared about as well as expected, scoring in between the 660-powered ZenFone 4 and the 625-powered Xiaomi Redmi 5 Plus. Surprisingly, AI Boost actually lowered the ZenFone 5's score here quite a bit. This test is run in Chrome, so I didn't expect it to make much of a difference, but it was over 100ms faster.


Basemark OS II

Basemark OS II is an all-in-one benchmarking tool that measures overall performance through a comprehensive suite of tests including system, internal and external memory, graphics, web browsing, and CPU consumption.

The ZenFone 5 performed a bit better here, and was closer to the higher performing 660-powered devices than the 625-powered Redmi 5 Plus. AI Boost also closed the gap a little further.


3DMark Sling Shot

3DMark Sling Shot is an advanced 3D graphics benchmark that tests the full range of OpenGL ES 3.1 and ES 3.0 API features including multiple render targets, instanced rendering, uniform buffers and transform feedback. The test also includes impressive volumetric lighting and post-processing effects. We're running this benchmark in Unlimited mode, which ignores screen resolutions.

In this benchmark, the ZenFone 5 was once again in between the ZenFone 4 and the Redmi 5 Plus. Unfortunately, AI Boost didn't do much for this benchmark, which suggests it's mainly for processor-intensive apps, and won't help much with graphics.




Like last year's ZenFone 4, the ZenFone 5 has a dual-camera setup at the rear pairing a 12-megapixel f/1.8 main lens with 4-axis OIS (optical image stabilization), with an 8-megapixel f/2.0 wide-angle lens. In addition, the ZenFone 5 also sports a newer Sony IMX363 image sensor.

Image quality from the main lens is quite good, especially for a mid-range phone, with good color reproduction, a high level of detail and contrast and fairly low noise. Auto-focus is fast and accurate, and only struggles in really poor lighting conditions. Shots tend to be slightly overexposed, and there is some slight lens distortion if you look closely, but it's not too bad overall.

Click for full-size image

Photos from the wide-angle lens show noticeable fisheye lens distortion, although color reproduction and contrast is still quite good. In general, you're better off using the main lens, but if you really need to take a big group photo and you can't back up any further, the wide-angle lens will do in a pinch.

Click for full-size image


AI-assisted photography

The camera now also boasts a number of AI features to help you take better photos.

We've already seen AI-assisted photography in Huawei and LG's phones, and ASUS's approach is fairly similar. The main AI feature is AI Scene Detection, which identifies the scene or subject a user is shooting and automatically applies the ideal settings for the best results. This takes into account things like color saturation, white balance, exposure and brightness, auto exposure time, sharpness, and noise. 

It is capable of detecting 16 different scenes:

  • People
  • Food
  • Dog
  • Cat
  • Sunset 
  • Sky
  • Green field
  • Ocean
  • Flower
  • Plant
  • Snow
  • Night view
  • Stage
  • Text
  • QR code
  • Tripod 

You'll notice the camera can distinguish between cats and dogs, and ASUS says that's because it wanted to take into account different expectations when shooting the two. For example, dog owners tend to have the luxury of having more time to frame the shot of their pup, whereas cat owners may want to capture their feline in action. In the latter case, the ZenFone 5 will apply a faster shutter speed.

The camera is generally quite good at identifying objects, but it can sometimes be fooled if there isn't enough context or two items look too similar.

The ZenFone 5 camera also uses AI to learn the type of photos that owners want through something called AI Photo Learning. The phone presents you with identical photos treated with slightly different image settings and lets you pick the one you like best. Over time, the camera comes to understand your preferences, and it then applies what it thinks is the best setting to replicate a similar look and feel for future shots.

The settings derived from AI Photo Learning also take precedence over those that the AI Scene Detection feature may suggest. However, not all scenes and subjects are supported, and compatible photos will be marked by an icon in your photo library. Unfortunately, I haven't really had enough time to notice AI Photo Learning do anything yet.

Other "AI" features include AI Beautification and AI Portrait, which works best for those who like to take selfies. The beautification mode is smart enough to detect the gender of subjects and apply digital makeup for women.

ASUS says it's analyzed over 100 different shades of skin color for the best results, and captures facial details using a scanning pattern with 365 dots. The effects can also be applied in video while live streaming on popular social media platforms.

Finally, AI portrait mode applies a bokeh effect to the background in real-time, and it works with both the front and rear cameras on the ZenFone 5.


Battery Life

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

  • Looping a 720p video with screen brightness and volume at 100%
  • Wi-Fi and Bluetooth connectivity turned on
  • Constant data streaming through email and Twitter

The ZenFone 5 has a 3,300mAh battery, which is about the average capacity for a phone of this size. The phone ran for 8 hours and 19 minutes, which was slightly better than the ZenFone 4 and Redmi 5 Plus, but fell far short of the Oppo R11s with its power-efficient AMOLED display. Running this benchmark with AI Boost turned on also resulted in a significant decrease in battery life, with over an hour lost. My advice is to only turn on AI Boost for CPU-intensive tasks, and only if the app is struggling without AI Boost.

The ZenFone 5 uses ASUS' own Boostmaster technology for fast charging, which charges the phone relatively quickly - you'll get about 50 percent charge in 30 minutes. The phone also includes an AI charging feature, which claims to "dynamically adjust the charging rate based on your previous charging behavior" This is supposed to extend the lifespan of your battery by varying the charging pattern to suit your usage habits. For instance, if the phone learns that you tend to go to bed at 10pm, it'll charge slower to reduce heat and avoid overcharging. Despite having a glass rear, the phone does not support wireless charging.



If you can get over the ZenFone 5's not particularly original design and features, it's actually a really nice phone that punches well above its weight. It looks and feels premium and offers a lot for its modest S$488 price tag.

Having said that, ASUS is really stretching the limits of what can be considered "AI", and I really don't appreciate it misleading consumers with its multitude of "AI" features that are clearly not, such as AI Display, AI Boost and AI Ringtone. It's not that these features aren't smart or useful, but they don't involve any machine learning, which is generally considered a requisite for AI. The only feature I consider where AI is actually being used on the ZenFone 5 is the AI image recognition in the camera.

ASUS has smartly priced the ZenFone 5 right below the usual crowd of budget flagships from the likes of Xiaomi and OnePlus, and as such, it doesn't have a lot of competition in its sub-S$500 price category. Other than a weaker processor, it actually compares quite favorably to more expensive phones like the Mi MIX 2 and OnePlus 5T. Its Snapdragon 636 isn't the fastest out there, but it handles most tasks fairly well, and if you mainly use your phone for web browsing, sending messages and watching videos, it's more than enough. If you really can't live without a top of the line processor, you can always wait for the Snapdragon 845-powered ZenFone 5Z, which will be available later this year, and should also be quite competitively priced.

Overall, the ZenFone 5 offers plenty of flagship features at a very reasonable price. After a misstep with last year's ZenFone 4, I'm happy to see a return to form for the ZenFone brand. If you're looking for great value without feeling like you're settling for a budget device, look no further.

  • Design 8
  • Features 7.5
  • User-Friendliness 8
  • Performance 7.5
  • Value 8.5
The Good
Premium look and feel
Great value
Decent camera
The Bad
Unoriginal design
Average performance
Misleading "AI" features