Asus Zenfone 4 Review

February 9, 2018 | Mark Goldstein | Rating star Rating star Rating star Rating star


The Asus Zenfone 4 is a flagship smartphone at a mid-range price, with a strong emphasis on photography. Designed to be a smartphone for keen photographers, the Asus Zenfone 4 has a 12-megapixel 1/2.55-inch sensor rear-facing camera with a 25mm f/1.8 lens, 4-axis optical image stabilisation which provides 4 stops of compensation, and Dual Pixel Phase Detection Auto Focus (PDAF) that's as quick as 0.03 seconds. Intriguingly there's also a second 8-megapixel rear-facing camera with a 12mm equivalent lens for a super-wide angle of view. Other standout features include RAW file support, a PRO shooting mode that lets you adjust the key camera settings, a maximum shutter speed of 32 seconds, 48 megapixel Super resolution mode, 4K UHD (3840 by 2160) video recording at 30fps, 120˚ wide-angle video, Slow Motion video, an 8 megapixel front camera, 64Gb built-in storage and a 5.5-inch FHD IPS screen. The Asus Zenfone 4 is priced at around £450 in the UK, unlocked and sim free.

Ease of Use

Asus Zenfone 4
Front of the Asus Zenfone 4

The Zenfone 4 is Asus' answer to the popular OnePlus 5, with a similar size, styling and cost Both devices attempt to deliver a premium experience at a more palatable price-point than the likes of Apple, Samsung et al.

For photographers, the Zenfone 4 tries to stand out from the crowd by featuring not one, but two rear-facing cameras, which offer 25mm and 12mm focal lengths respectively. So, at the push of an on-screen icon, you can switch from a fairly wide 25mm angle of view to one that captures a 120-degree view, albeit with a drop in resolution from 12 to 8 megapixels. We haven't tested a smartphone that offers this before, and in practice found it to be very useful in certain situations, although the resulting image does suffer from a lot of barrel distortion that you'll either need to live with or remove in post-processing.

The Asus Zenfone 4 has another ace up its sleeve in the form of very fast auto-focusing, thanks to the on-sensor Dual Pixel Phase Detection system. The quoted AF speed of 0.03 seconds is very quick indeed for a smartphone, and even better, it also works almost as quickly and reliably in less than stellar lighting conditions. On the whole, you'll quickly forget about the Asus Zenfone 4's autofocusing because it's just so quick and reliable.

Asus Zenfone 4
Rear of the Asus Zenfone 4

4-axis optical image stabilisation is another great feature, which provides 4 stops of compensation when hand-holding the device. As the Zenfone 4's ISO range tops out at ISO3200, with image quality starting to suffer at ISO800, it's a really good thing that OIS is onboard, helping to keep the picture sharp in low-light situations where otherwise you'd get blurred images, or ones with lots of noise if you were forced to choose a higher ISO speed. Note that when shooting video, the Zenfone's camera employs 3-axis electronic image stabilization, which sadly isn't on a par with the still camera system.

If OIS doesn't cut it, you can always mount the Zenfone 4 on a tripod using an optional grip and take advantage of the maximum shutter speed of 32 seconds, again a feature that few smartphones offer. This allows you take proper long exposure night photographs, such as capturing traffic light trails, whilst locking the ISO at 25 to help keep the noise levels down.

Further appealing to more serious photographers is the inclusion of RAW file support in the form of DNG files, allowing you a lot more flexibility in post-processing than shooting just JPG files.

Asus Zenfone 4
The Asus Zenfone 4 In-hand

There's also a PRO shooting mode which allows you take control of most of the camera's key exposure settings - AF, Shutter Speed, ISO, EV and WB all become available via an intuitive row of icons at the bottom of the camera interface. This is something that we really missed on the Google Pixel 2's native camera interface, and which we found straight-forward to use on the much cheaper Asus Zenfone 4.

Naturally for a 2017 device, the Zenfone 4 includes video at 720P, 1080P (60fps) and 4K (30fps) resolution, complete with electronic stabilization. There's also slow-motion, GIF animation and time-lapse modes if you want to get even more creative.

The only standout feature that doesn't hit the target (at all) is the rather ambitious 48 megapixel Super resolution mode, which attempts to provide an image 4x larger than the one captured by the main camera. The resulting photos may have more pixels, but they also suffer badly from a lack of clarity and sharpness, so badly that we'd recommend just ignoring this feature altogether.

Still, the Asus Zenfone 4 gets a lot more things right than it does wrong, offering a surprisingly feature-rich and well-implemented photographic experience for beginner and serious snappers alike. Now let's take a look at its image quality...

Image Quality

All of the sample images in this review were taken using the 12 megapixel JPEG setting, which gives an average image size of around 4Mb.


The Asus Zenfone 4 has 8 manually-selectable ISO sensitivity settings available at full resolution, ranging between ISO 25 and ISO 3200.


ISO 25 (100% Crop)

ISO 25 (100% Crop)

iso25.jpg iso25raw.jpg

ISO 50 (100% Crop)

ISO 50 (100% Crop)

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ISO 100 (100% Crop)

ISO 100 (100% Crop)

iso100.jpg iso100raw.jpg

ISO 200 (100% Crop)

ISO 200 (100% Crop)

iso200.jpg iso200raw.jpg

ISO 400 (100% Crop)

ISO 400 (100% Crop)

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ISO 800 (100% Crop)

ISO 800 (100% Crop)

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ISO 1600 (100% Crop)

ISO 1600 (100% Crop)

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ISO 3200 (100% Crop)

ISO 3200 (100% Crop)

iso3200.jpg iso3200raw.jpg

Focal Range

The Asus Zenfone 4's main fixed focal length lens is equivalent to 25mm in 35mm camera terms. It also has a second 8 megapixel rear camera with a lens that is equivalent to a super-wide focal length of 12mm in 35mm camera terms.





Super Resolution

The Super Resolution mode captures a 48 megapixel image, 4x larger than the native resolution of the main camera, but the resulting image suffers from a distinct lack of fine detail, so much so that we wouldn't recommend using it.



super_res_off.jpg super_res_on.jpg


The Asus Zenfone 4 is able to focus as close as about 5cm from a subject. We found this claim to be accurate, though autofocusing does occasionally struggle to lock on at this kind of range.




The Asus Zenfone 4 uses a LED flash, and as usual for this technology, it gives a weaker flash burst than a standard xenon camera flash.

Flash Off


Flash On

Selfie Mode


Thanks to the 4-axis optical image stabilisation system, wide f/1.8 maximum aperture and maximum shutter speed of 32 seconds, the Asus Zenfone 4 performs well at night. This image was taken at the camera's ISO 25 sensitivity at a shutter speed of 32 seconds, and though there's some noise and detail smoothing, the result is still comparable to what a typical compact camera would produce.




The Asus Zenfone 4's automatic sweep panorama mode works well and lets you stop panning at will. The results aren't always perfect, but ghosting is rare. The Asus Zenfone 4 has enough processing power to capture panoramas at fairly high resolutions - they are usually around 992 vertical pixels, with a maximum width of 9600 pixels.


Sample Images

This is a selection of sample images from the Asus Zenfone 4 camera, which were all taken using the 12 megapixel JPEG setting. The thumbnails below link to the full-sized versions, which have not been altered in any way.

Sample Movie & Video

This is a sample movie at the highest quality setting of 3840x2160 pixels at 30 frames per second. Please note that this 14 second movie is 75Mb in size.

Product Images

Asus Zenfone 4

Rear of the Asus Zenfone 4

Asus Zenfone 4

Rear of the Asus Zenfone 4

Asus Zenfone 4

Rear of the Asus Zenfone 4

Asus Zenfone 4

Front of the Asus Zenfone 4

Asus Zenfone 4

Front of the Asus Zenfone 4 / Image Displayed

Asus Zenfone 4

Front of the Asus Zenfone 4 / Android OS

Asus Zenfone 4

Front of the Asus Zenfone 4 / Camera Mode

Asus Zenfone 4

Front of the Asus Zenfone 4 / Pro Mode

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Front of the Asus Zenfone 4 / Settings

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Front of the Asus Zenfone 4 / Shooting Modes

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Front of the Asus Zenfone 4 / Filters

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Side of the Asus Zenfone 4

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Bottom of the Asus Zenfone 4

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Top of the Asus Zenfone 4

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Front of the Asus Zenfone 4

Asus Zenfone 4

Front of the Asus Zenfone 4


Asus might not be the first name that you think of when buying a new smartphone, and its mid-range price perhaps leads you to expect a solid device, rather than spectacular one, but the Zenfone 4 certainly offers a lot of photographer-friendly features that are well-thought-out and well implemented. 

The auto-focus system is speedy and reliable, the optical image stabilisation helps in low-light, the PRO shooting mode is both comprehensive and intuitive to use, and RAW file support is the icing on the cake. 

It even has a few ace cards of its own, with the 120-degree second main camera/lens in particular offering something different to most dual-lens smartphones, which typically use the second camera to either help simulate bokeh or extend the zoom range. 

The Zenfone 4's design may look a little, well, conservative at a time of bezel-less displays, the CPU isn't the fastest in its class, and battery life from the 3300mAh battery is good enough, rather than great, but Asus' flagship phone is still well worth considering as a solid mid-range phone that offers a very good photographic experience.

4 stars

Ratings (out of 5)
Design 3.5
Features 4
Ease-of-use 4
Image quality 4
Value for money 4.5

Main Rivals

Listed below are some of the rivals of the Asus Zenfone 4.

Apple iPhone X

The Apple iPhone X is the most anticipated smartphone of 2017, but can its photographic capabilities really satisfy the keen photographer? Read our in-depth Apple iPhone X review to find out...

Google Pixel 2

According to DXO, the Google Pixel 2 offers the best image quality of any smartphone currently on the market, but is it really the best option for photographers? Read our in-depth Google Pixel 2 review to find out...

HTC One (M9)

The HTC One (M9) is a new flagship Android smartphone with a conventional 20 megapixel sensor, 5-inch screen, RAW file support and a MicroSD card slot. Read our HTC One (M9) review to find out if it can satisfy the photographer in you...

Huawei Mate 10 Pro

The Mate 10 Pro is the latest flagship phone from the Chinese manufacturer Huawei, and as with a lot of new smartphones these days, it promises a lot for the keen photographer, not least Leica-branded f/1.6 lenses and dual colour / monochrome image sensors. Read our in-depth Huawei Mate 10 Pro review for photographers now...

Kodak Ektra

The new Kodak Ektra is billed as the perfect smartphone for keen photographers, from enthusiasts to experts, but does it offer enough to replace the smartphone that's currently in your pocket? Find out by reading our Kodak Ektra review...

Sony Xperia XZ1

The Sony Xperia XZ1 is a new flagship smartphone that's a little more affordable than the other flagships out there. For photographers, it offers a 19 megapixel Exmor RS sensor, f/2 25mm Sony G branded lens, 4K video recording, and a manual shooting mode. Read our Sony Xperia XZ review now to find out more about Sony's latest handset...

Review Roundup

Reviews of the Asus Zenfone 4 from around the web. »

The mid-range ZenFone 4 is Asus’ latest flagship smartphone. With pricing starting at £450, it targets the same segment of the market as the stellar OnePlus 5, which to date is TrustedReviews’ recommended sub-£500 handset.
Read the full review » »

Asus may not be the best-known name in smartphones, but it has an extensive range of devices available in the U.S. and the U.K., at fairly reasonable prices. The brand name has a good following, largely due to its computers, but Asus has a quirky history with mobile products — releasing niche devices that often seem more experimental than anything else. Last year it unveiled the ZenFone AR smartphone utilizing Google’s soon-to-be-dead Tango augmented reality program; and even older devices like the Asus PadFone toyed with the idea of a smartphone combined with a tablet. As rumors about the ZenFone 5 heat up, we’re looking at the ZenFone 4, a phone that couples an unusual wide-angle camera with a slick design, and an affordable $400 price tag.
Read the full review » »

Are you tired of having a phone your friends recognise? The sheer weight of that iPhone cred getting you down? An Asus ZenFone 4 is one way to get back to your humble roots with a phone only the nerdiest of mobile lovers would recognise. It’s not like Asus is some phone-making newbie, though.
Read the full review »


ZenFone 4 (ZE554KL)
Finish / Color

Moonlight White, Midnight Black


Internal storage


MicroSD card

Supports up to 2TB

Google Drive

100GB free space (1 year)

Weight and Dimensions
(6.11 inches) 75.2mm
(2.96 inches) 7.5mm
(0.29 inches)

Weight: 165 grams (5.82 ounces)


5.5-inch Full HD (1920 by 1080) Super IPS+ display

600nits brightness

Front and rear strong 2.5D Corning® Gorilla® Glass

2.1mm slim bezel

Bluelight filter for eye care

Capacitive touch panel with 10 points multi-touch (support glove touch)

Smudge-resistant oleophobic coating


CPU: Qualcomm® Snapdragon™ 660 Mobile Platform with 14nm, 64-bit Octa-core Processor
Qualcomm® Snapdragon™ 630 Mobile Platform with 14nm, 64-bit Octa-core Processor
FinFET LPP (Low Power Plus) powersaving technology

GPU: Qualcomm® Adreno™ 512 (SD660)
Qualcomm® Adreno™ 508 (SD630)



Main Rear Camera

5x light sensitivity low light photos (compared with a typical camera with 16 megapixels, F1.7 & 1.12µm pixel size)

Sony flagship IMX362 12 megapixels dual pixel image sensor - 1/2.55" large sensor size, 1.4µm large pixel size

F1.8 aperture

25mm equivalent focal length in 35mm film camera

6p lens

83° field of view

0.03 seconds Dual Pixel PDAF

0.03 seconds subject-tracking auto-focus

4-axis, 4 stops optical image stabilization

Color correction (RGB) sensor

LED flash

Instant cameras switching

PixelMaster camera modes:

Auto (with low light and HDR features)



Pro (RAW file support / up to 32 seconds long exposure)

Super Resolution (48 megapixels)

GIF Animation


Slow Motion

Time Lapse (with power saving)

9 various filters

Second Rear

8 megapixels

120° wide-angle camera

200% wider view for more friends and scenery in the frame

12mm equivalent focal length in 35mm film camera

Video Recording

4K UHD (3840 by 2160) video recording at 30 fps for main rear camera

1080p FHD video recording at 30 / 60 fps

720p HD video recording at 30 fps

3-axis electronic image stabilization for rear camera's shake-free videos

120˚ wide-angle video

Slow Motion video (1080p at 120 fps / 720p at 240 fps)

Take still photo while recording video

Front Camera

8 megapixels

F2.0 aperture

24mm equivalent focal length in 35mm film camera

84° field of view

PixelMaster camera modes:

Auto (with low light and HDR features)



Selfie Panorama

GIF Animation

9 various filters



Dual speakers

5-magnet speaker with NXP Smart Amp for up to 40% better performance

Audio Output

Hi-Res audio 192kHz/24-bit standard that is 4 times better than CD quality

DTS (Digital Theater System) Headphone:X™ 7.1 virtual surround sound for headphone support

Audio CODEC integrated into PMIC


Dual internal microphones with ASUS Noise Reduction Technology

FM Receiver

FM radio

Wireless Technology

WLAN 802.11 a/b/g/n/ac

Bluetooth 5.0

Wi-Fi direct




SIM Cards

Dual SIM dual standby

Slot 1: 2G/3G/4G Nano SIM card

Slot 2: 2G/3G/4G Nano SIM card, or the MicroSD card (supports up to 2TB) at a time

Both SIM card slots support 3G WCDMA / 4G LTE network band. But only one SIM card can connect to 3G WCDMA / 4G LTE service at a time.

Network Standard


Data rate

LTE Cat12 UL 150 / Cat13 DL 600 Mbps

DC-HSPA+: UL 5.76 / DL 42 Mbps

2CA / 3CA support (by specification and region)

Operator with NFC version

FDD-LTE (Bands 1, 2, 3, 5, 7, 8, 18, 19, 20, 26, 28, 32)

TD-LTE (Bands 38, 39, 40, 41)

WCDMA (Bands 1, 2, 3, 5, 6, 8, 19)

EDGE/GPRS/GSM (850, 900, 1800, 1900MHz)

CN with NFC version

FDD-LTE (Bands 1, 2, 3, 5, 7, 8)

TD-LTE (Bands 34, 38, 39, 40, 41)

WCDMA (Bands 1, 2, 5, 8)

TD-SCDMA (Bands 34, 39)

CDMA (Band BC0)

EDGE/GPRS/GSM (850, 900, 1800, 1900MHz)

TW-2CA with NFC version

FDD-LTE (Bands 1, 2, 3, 5, 7, 8, 18, 19, 28)

TD-LTE (Bands 38, 39, 40, 41)

WCDMA (Bands 1, 2, 3, 5, 6, 8, 19)

EDGE/GPRS/GSM (850, 900, 1800, 1900MHz)

TW-3CA with NFC version

FDD-LTE (Bands 1, 2, 3, 5, 7, 8, 18, 19, 28)

TD-LTE (Bands 38, 39, 40, 41)

WCDMA (Bands 1, 2, 3, 5, 6, 8, 19)

EDGE/GPRS/GSM (850, 900, 1800, 1900MHz)

WW/ID/IN without NFC version

FDD-LTE (Bands 1, 3, 5, 7, 8, 20)

TD-LTE (Band 40)

WCDMA (Bands 1, 5, 8)

EDGE/GPRS/GSM (850, 900, 1800, 1900MHz)

BR without NFC version

FDD-LTE (Bands 1, 2, 3, 4, 5, 7, 8, 12, 17, 28)

WCDMA (Bands 1, 2, 4, 5, 6, 8)

EDGE/GPRS/GSM (850, 900, 1800, 1900MHz)

NA/SA with NFC version

FDD-LTE (Bands 1, 2, 3, 4, 5, 7, 8, 12, 17, 28)

WCDMA (Bands 1, 2, 4, 5, 6, 8)

EDGE/GPRS/GSM (850, 900, 1800, 1900MHz)

ASUS phone 4G/LTE band compatibility varies by region, please check compatibility with local carriers.


Front fingerprint sensor (0.3 seconds unlock, supports 5 fingerprints), Accelerator, E-Compass, Gyroscope, Proximity sensor, Ambient light sensor, Hall sensor

External Buttons and Connectors
Fingerprint sensor On/Off
Sleep/Wake Volume up/down 3.5mm audio jack
(1 Headphone / Mic-in) Built-in speaker USB-C connector

3300mAh with fast charging

5 minutes charge for 2 hours talk time

36 minutes charge to 50% capacity

Up to 23 days 4G standby

Up to 30 hours 3G talk time

Up to 16 hours video playback

Up to 18 hours Wi-Fi web browsing

Power Adapter

Output: 9V 2A 18W* & 5V 2A 10W**

* The ZenFone 4 with a Qualcomm® Snapdragon™ 660 Mobile Platform comes equipped with a 18W charger but charge is limited to 15W for technical and safety reasons.

** The ZenFone 4 with a Qualcomm® Snapdragon™ 630 Mobile Platform comes equipped with a 10W charger.

Operating System

Android™ N with new ASUS ZenUI 4.0

ASUS ZenUI includes:

ZenUI Safeguard
Fingerprint Sensor
ASUS MyCover
File Manager
Game Genie
Mobile Manager
Page Marker
In the Box

ZenFone 4 with Android™ N and new ASUS ZenUI 4.0

ASUS earphone with microphone

Type-C USB cable

Ejector pin (SIM tray needle)

USB power adapter (SD660 / 15W)

USB power adapter (SD630 / 10W)

Documentation (user guide, warranty card)

Clear soft bumper (optional)


Specifications and contents may vary by region.

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