ASUS ZenFone 8 review: A small flagship phone filling big boots

Note: This review was first published on 14 June 2021.

Cornering the compact flagship segment

While we’ve been treated to flashy, powerful ROG Phones by ASUS of late, the Taiwanese tech brand was quieter on the mainstream phone front - until this year. ASUS was chuffed to announce and bring the ASUS ZenFone 8 to the Singapore market. In its product introduction, the brand said that it not only packs the highest-end parts that make a flagship phone, but also several key features that make it ideal for folks who don’t want massive phones.

That’s right - the ASUS ZenFone 8, despite packing a Qualcomm Snapdragon 888 chipset within, has a really small and compact body. It’s even smaller than the Samsung Galaxy S21 and just a touch larger than the Apple iPhone 12 Mini, making it one of the smallest Android flagship alternatives from 2021 we have here. You could probably say Android fans who've been hugging a Samsung Galaxy S10e, now finally have a high-end compact phone that doesn't skimp on flagship experiences. ASUS also piled on several optimisations, like One-Handed Mode, to make the phone’s design language sensible for folks who like their phones small and powerful.

The ZenFone series also saw some grafting of the ROG Phone heritage to its series. In a bid to stay competitive, ZenFone 8 offers an 1080p AMOLED display that not only has 120Hz refresh rate, but also 240Hz touch response rate and 1ms response time. So, if you like having a super responsive phone that’s also great at graphics, ZenFone 8 has that corner covered. 

If the past is any indication, ASUS also prides itself on its phones' imaging quality. This time, ZenFone 8 offers a triple camera system (dual rear, single front) that uses Sony IMX sensors across all modules. The 64MP main camera is backed by a Sony IMX686, while the 12MP ultra-wide camera has a Sony IMX363. The front camera is also 12MP and it runs on a Sony IMX663 sensor. It’s not as crazily outfitted as many other Android alternatives, so it’s really down to testing to see if ZenFone 8 holds up for photography.

The greatest drawbacks to small phones are the limits of size. Not only will we be paying attention to any trade-offs in favour of miniaturisation, but the ZenFone 8 can also only fit a 4,000mAh battery with 30W fast-charging (same battery size as the Galaxy S21 base model). Also, ZenFones have had a history of having strange or bloated user experiences thanks to its love for packing in one-trick ponies, so we’re also on the lookout for that, too.

Will the S$999 ASUS ZenFone 8 hold up in a competitive market with the likes of Xiaomi Mi 11, Samsung Galaxy S21, and other S$1,000+/- alternatives threatening to deny its return? Is the ASUS ZenFone 8 even a good, flagship-grade compact phone for the Android camp? Let’s find out. 

Design & Handling

Durability and comfort are at the forefront of the ZenFone 8’s appearance and handling. ASUS is very insistent that users know it’s optimised for one-handed use through its form factor and interface tweaks.

It’s dimensions (148 x 68.5 x 8.9mm) makes it one of the most compact modern Android smartphones available in Singapore. It’s slightly smaller than the regular Samsung Galaxy S21, and the closest physical match to a ZenFone 8 is the Google Pixel 4a (144 x 69.4 x 8.2mm). While the Pixel 4a is mid-range phone, the real comparison would be against an even more compact phone from Samsung, the Galaxy S10e (142.2 x 69.9 x 7.9 mm), which is a true compact flaghip Android from 2019 that hasn't seen a suitable candidate to displace its class,  until now. Despite the ZenFone 8's tad larger dimensions, it truly fits in one average-sized hand that there’s no need to stretch your opposable thumb to reach the other side of the screen. 

The same thumb can cover about 75% of the screen’s length. Despite its compact size, the ZenFone 8 is still larger than an Apple iPhone 12 Mini, making the ASUS flagship feel less claustrophobic than Apple’s during use.

The added touch to comfort comes from ASUS’s One-Handed Mode. Flicking a finger downwards at the display’s bottom end would bring the upper extremities of the app down - within thumb’s reach. It’s almost identical to the iPhone’s Reachability display - only that the latter is triggered by double-tapping the bottom instead of swiping down. One-Handed Mode is applied throughout the phone’s interface, so it works on non-app functions, like accessing the Quick Settings pull-down menu.

One-Handed Mode’s height (or rather, the amount it pulls down) can be customised under the Settings app. Simply go to Advanced, and then tapping on the words One-Handed Mode (not the toggle), followed by Change Height Settings. The lowest it goes is mid-way of the screen’s length, with room to reduce the amount it drops down. Hitting the toggle would disable the feature entirely if you’re not keen on using it. 

ZenFone 8 uses a plastic rear with frosted glass appearance, and a matte aluminium frame. Both are popular material choices for flagship Android phones consummate with its asking price. 

The extra touch comes from the front panel, which uses Corning’s Gorilla Glass Victus for added scratch resistance. The rear’s glass panel uses Gorilla Glass 3. For comparison, the Mi 11 also had the same glass technology at the front, but the Xiaomi phone uses a newer and more durable Gorilla Glass 5 for the rear.

What the ZenFone 8 does have against the Mi 11 is IP65/IP68 rating, a feature we’ve come to expect in any smartphone that calls itself flagship-grade. 

All in all, ZenFone 8 has a very safe and comfortable design, if a little dated, when placed next to other splashy, high-end handsets like the ROG Phone 5.

Display & Audio

A small phone begets a small display. The ASUS ZenFone 8 has a 5.9-inch, Samsung E4 AMOLED display rated at 2,400 x 1,080 pixels resolution. That works out to a pixel density of 445 PPI, making it plenty sharp to the eye. 

The display also packs plenty of features worthy of its flagship status. It has 120Hz refresh rate, 240Hz touch sampling rate, 112% reproduction of DCI-P3, 151.9% of sRGB colour gamut, with a ΔE of less than 1.0. In English, that means the ZenFone 8’s display is not only super responsive and fluid, but it’s also colour-accurate enough for professional use. The cherry on top is the certification for HDR10 and HDR10+, making it suitable for HDR streamed content from your favourite video-watching platforms.

Unlike most flagship Android phones with adaptive refresh rates that only goes up to 120Hz when called upon, the ZenFone 8 offers toggles to fix the display’s refresh rate at 60Hz, 90Hz, and 120Hz. This granularity is on top of offering a default “Auto” toggle which refreshes based on the app’s intensity (e.g. text-based or apps brings it down to 30Hz). It’s great having control over refresh rates, but know that forcing 120Hz is likely going to deplete your battery faster than usual. If you’re coming from other modern Android phones, most of them have adaptive refresh rates enabled by default.

The ZenFone 8 features two linear speakers that have dual Cirrus Logic Mono amplifiers. At the same time, its 3.5mm audio jack is further supported by a built-in Qualcomm Aqstic DAC (one of the perks of using SD888). For us, having a 3.5mm headphone port is a nice touch, even if we’ve come to terms with wireless personal audio (ZenFone 8 offers Bluetooth 5.2).

UI & Features

Given the phone’s size, One-Handed Mode is arguably the most important software feature of the ZenFone 8. However, we’ve covered that under the Handling portion of our review.

That leaves us with the rest of the ZenFone 8, which comes with Android 11 cloaked under ZenUI - the brand’s proprietary user interface for its smartphones and tablets. The current version of ZenUI is the cleanest smartphone UI we’ve seen out of ASUS thus far, because it retains some of stock Android 11’s design and ‘bloatware’ was kept to a minimum. The UI is slightly cleaner than the 2018 ZenFone 5, with the ZenFone 8 using a neutral palette and bold primary colours.

ASUS’s onboarded apps aren’t very intrusive since they offer additional functions. For example, ASUS ShareMe is a local file transfer app that uses Bluetooth and Wi-Fi connectivity, without needing to go online. ASUS Data Transfer facilitates importing and exporting between old and new Android/iOS devices. There are also extra file management and video player apps, but they can be easily removed if you’re already comfortable with ASUS’s or Google’s default ones. 

A small, yet notable feature is Smart Key. In typical Android devices, the Power button is usually not customisable - either it locks and powers off the phone, or it can be used to summon its voice assistant when held down (usually Google Assistant). ZenFone 8’s power button can be programmed to bring two shortcuts instead of Google Assistant. The shortcuts let you fire up an app of your choice, or to do an action (like toggling your hotspot/Wi-Fi, taking a screenshot, enabling or disabling auto-rotation, etc.). This feature is hidden under Settings > Advanced > Smart Key. 

An odd behaviour on the ZenFone 8 lies in the phone’s default wake-up routine. When in standby, the ZenFone 8 will show its always-on display, and you need to hit the Power button once to begin unlocking your device. The delay between AOD and proper lock screen is almost a full second, which is unlike other Android or iOS smartphones - auto-wake upon pick-up, or near-instant wake after pressing the button. 

If you want a more seamless user experience with the ZenFone 8, we highly recommend enabling both “double-tap to wake up” and “swipe up to wake-up” under the the Gestures sub-menu of Settings app. These are display commands that bypass the Lock button. The delay in waking the phone up with either of those options is also much shorter than the wait after hitting the Lock button.

The actual unlocking itself (PIN, in-display fingerprint sensor, and face recognition) were all otherwise fast and responsive. NFC itself had no hitches either.

The ZenFone 8 has two SIM card slots for folks on two mobile plans, but the phone lacks a microSD card slot. Recent Android alternatives like the Xiaomi Mi 11, Vivo X60 Pro, and Samsung Galaxy S21 also do not have physical expandable storage, so it’s a trend we’re seeing in phones of late.

Imaging Performance

The ASUS ZenFone 8 uses a three-camera system - two on the rear and one at the front. The dual rear consists of:

• A 64MP main camera with a 1/1.17-inch Sony IMX686 sensor, accompanied by OIS, Quad Bayer filter (0.8μm/1.6μm effective pixel size), f/1.8 aperture, 2x1 OCL PDAF, and 8K video recording with EIS at 24 FPS.
• A 12MP secondary camera with a 1/2.25-inch Sony IMX363 sensor, 1.4μm pixel size, f/2.2 aperture, Dual PDAF, real-time distortion correction, and a 113 ̊ field of view. It also has a 4cm macro shooting distance, with 4K recording at 60 FPS.

In a nutshell, the main camera offers generic shooting needs with wide angles, while the secondary camera handles ultra-wide angle shots and macro shots. At least one camera is capable of 4K60FPS recording too. Other features built into the rear cameras are the ability to grab still images from videos (not applicable to 8K recordings), Motion Tracking video (up to 4K60FPS), Time Lapse recording (4K60FPS), and Slow Motion recording (4K120FPS). 

Noticeably, there is no optical zoom feature or telephoto-specific camera, unlike most other Android flagships. Instead, zooming on ZenFone 8 is handled digitally. Despite that, the phone has Ozo Audio Zoom, a Nokia-made digital spatial audio technology that corresponds to recorded sounds based on the zoomed subject while eliminating background noise (the same tech can be found in the Oppo Find X2 Pro).

The front camera is a 12MP Sony IMX663 with a 1/2.93-inch sensor, 1.22μm effective pixel size, f/2.45 aperture, Dual PDAF. It can record videos up to 4K at 30FPS. This is the first phone to carry a Sony IMX663 sensor.

Unlike many Android smartphone makers with vague or confusing wording for its camera specs, ASUS is very clear about what the ZenFone 8’s rear cameras are supposed to deliver. So, let’s see if they hold up.

Sample images

The ZenFone 8's main camera is slightly aggressive when exposing whites and lighter areas, but it's otherwise a competent shooter for everyday situations. It has great colourisation and detailing, and it has excellent control over image noise. In this sample image, the ZenFone 8 makes it easy to work out the items on sale and capture subtle tricks of light like transparent plastic packaging on certain foodstuff.

The ultra-wide camera offers a more natural-looking reproduction of the scene, likely because it doesn't overexpose shots like the main camera. In addition, the fish-eye distortion correction seems pleasant - still some traces exist, but not jarring unless you're really looking for a fish-eye effect.

No optical zoom? No problem. The ZenFone 8 offers a maximum of 8x digital zoom via its main camera, and we liked how it kept noise to a minimum. But, of course, it's not perfect since it's digital zoom after all, and some digital compensation needs to be in place - check out the artefacts on the left-sided tree.

As mentioned, macro shots on the ZenFone 8 are delegated to the ultra-wide-angle rear shooter with its '4cm focusing distance' feature. Our only real complaint? The focusing distance demanded by the phone needs more than 4cm, even if the focal point seems to be at 4cm - you can get good macro shots on the ZenFone 8 but do not expect it to be a breeze.

That covers the general imaging quality offered by the ZenFone 8. As a whole, the phone's camera system is good at what it does and is mostly snappy and responsive. The image quality turned out a little better than what we had in mind before we tested the device. Below are more samples for reference.

Benchmark Performance

The ASUS ZenFone 8 contains the Qualcomm Snapdragon 888 chipset. It puts the phone in the running as a 2021 flagship Android smartphone against competitors with identical chipsets - like the Xiaomi Mi 11 and Oppo Find X3 Pro. Competitors with flagship-tier chipsets built on a similar manufacturing process, like the Exynos 2100, are also up for consideration, pitting the ASUS phone against the Samsung Galaxy S21 series as well.

The ZenFone 8 variant we have on hand also comes with 16GB LPDDR5 RAM and 256GB UFS 3.1 internal storage, which costs S$100 more than the 8GB RAM based model at S$999. This should lend it additional processing power next to all other comparison phones that typically 'only' have 8 to 12GB. 

We’ve pit it against phones with SD888 (Xiaomi Mi 11, Oppo Find X3 Pro), SD888-equivalents (Samsung Galaxy S21), and friends of similar physical sizes, even if they offer dissimilar performance (Apple iPhone 12 Mini, Google Pixel 4a). We’ve also thrown in an SD865 phone from last year to compare against 2020’s flagship chipset and devices (OnePlus 8T).

JetStream 2.0

JetStream 2 is a combination of a variety of JavaScript and Web Assembly benchmarks, including benchmarks that came before like SunSpider and Octane. It primarily tests for a system’s and browser’s ability in delivering a good web experience. It runs a total of 64 subtests, each weighted equally, with multiple iterations, and takes the geometric mean to compute the overall score.

AnTuTu 

Note: As of 9th March 2020, all AnTuTu benchmarks were removed from the Google Play Store. This move likely arose from Google's attempts to relieve the Play Store of apps that violate their policies. AnTuTu is working with Google to restore their app listing. For this review, we used the APK file that was available on AnTuTu's website.

AnTuTu is an all-in-one benchmark that tests CPU, GPU, memory, and storage. The CPU benchmark evaluates both integer and floating-point performance, and the GPU tests assess 2D and 3D performance, the memory test measures available memory bandwidth and latency, and the storage tests gauge the read and write speeds of a device's flash memory.

Geekbench 5

Geekbench CPU is a cross-platform processor benchmark that tests both single-core and multi-core performance with workloads that simulate real-world usage. Geekbench 5 scores are calibrated against a baseline score of 1000, which is the score of an Intel Core i3-8100.

3DMark Sling Shot Extreme

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. The test's Unlimited mode ignores screen resolutions.

We’re also collecting scores with 3DMark’s new benchmark, Wild Life. Below are the test’s Unlimited Mode scores.

Performance Benchmark Remarks

Overall, the ZenFone 8’s benchmark performance is on par with other SD888 touting devices. Sure, it may perform better in certain metrics and worse in others, but all of it evens out to a high-performing 2021 smartphone.

What got us was how ZenFone 8 didn’t let its size get in the way of performing well, which was something we noticed in the Galaxy S21. In real-world usage, any hiccups experienced were down to UI and animation choices - the phone was capable of handling anything we threw at it.

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

The ZenFone 8 offers a 4,000mAh battery with a 30W HyperCharge adapter in the box for fast charging. The phone offers Quick Charge 4.0 and PD charging profiles, but ASUS didn’t outright state the maximum charging speed the ZenFone 8 has. 

We think its 804 minutes of uptime is very respectable. It’s reminiscent of ASUS’s improved battery handling in its past ZenFone models. Having a less demanding 1080p display helps immensely too (the other alternatives like Xiaomi and Oppo on this list were running the test with a 1440p display). The closest rival it has is the Galaxy S21 with similar display specs and a 5nm chipset, but ZenFone 8 was able to get 200 more minutes. Mi 11 and Find X3 Pro’s performance could be chalked up to its higher-rated 1440p display, which likely draws more power.

Fast-charging took only 35 minutes to go from 0% to 50%, but 99 minutes total to go from 0% to 100%. Even with default battery settings, the ZenFone 8 is careful when it comes to fast-charging, where the charging speed tapers off as it approaches a full battery. That said, if you prioritise having a full charge within an hour, you can go into the settings and tweak its battery management features to make it more aggressive.

Noticeably, the ZenFone 8 lacks wireless charging, a feature available in many devices at its price point. 

Conclusion

Our gauntlet of tests and our experiences with the ZenFone 8 tells us it’s a good flagship smartphone that feels sensible to use, with performance that’s up to par, along with features of respectable quality - like its battery and camera work. Starting at S$999, the ZenFone 8 would make a great choice if you’re looking to upgrade from a premium midrange phone - more so if it’s an ageing one.

Where it does fall a little short are its other user experiences, which we’ve covered in our Features section and also managed to work around with some effort. It’s also a phone that requires a careful look into its Settings page in order to make it go above and beyond for you, but that also holds true for big-name brands. What really penalises it as a flagship offering, however, is the lack of wireless charging, and perhaps the lack of a telephoto lens - these are trade-offs needed to fit other components in the very small space it has.

With its price tag, it has to contend with the likes of the Xiaomi Mi 11, and the slightly pricier Samsung Galaxy S21 (which is probably more affordable now, given the passage of time and increased competition). Chipset performance aside, it’s a matter of trade-offs between these three options. Mi 11 has 1440p display when the other two do not, but ZenFone 8 fills an important gap that Xiaomi left out: IP-rated water resistance. Samsung’s Galaxy S21 aces in non-stock Android UI experiences with a similar size to boot, while ZenFone 8 has a much better battery life next to these rivals.

Of course, all these recommendations also consider that you accept and want a palm-sized device as your main consideration. It’s always a choice between a bigger screen against better portability. So, remember to factor in your tolerance between squinting and carrying bulky phones when deciding on the ZenFone 8.

That said, it’s almost unmatched in performance for a phone of its size, since existing smaller or equally small Android phones don’t carry the SD888 chipset as the ZenFone 8 does, and these small phones typically sacrifice battery uptime while the ZenFone 8 tries not to.

As a whole, the ZenFone 8 is a great phone facing greater competition. It’s also both a good and unique smartphone because of its compact size, worthy features, and palatable price, even if it’s not particularly flashy in any aspect. We welcome having more options in Singapore’s flagship Android space and finally, we can recommend a capable, high-end compact Android phone that's not from Samsung.

The trickier question then is should you choose the ASUS ZenFone 8 or the Samsung Galaxy S21 when hunting for a compact flagship phone? As iterated earlier, the Galaxy S21 has the upper hand in non-stock Android UI experience all through its operating system, a better camera system with its dedicated telephoto lens and a more capable, advanced and yet user-friendly camera interface, wireless charging and a more polished phone design as a whole. Where the ZenFone 8 gets the nod is its overall performance, much better battery life and being a tad more affordable. So it's a matter of which set of experiences do you want more out of your device.

The ASUS ZenFone 8 is available for purchase at an official recommended price of S$999 (8GB RAM + 256GB storage), with a S$1,099 alternative (16GB RAM + 256GB storage). If you’re convinced that it’s a flagship phone worthy of your money, you can purchase one from ASUS' online store.