Here at PCAdvisor we are surprised at how much we like Asus's new line of smartphones. The ZenFone range includes three smartphones: the ZenFone 6 with a 6in display, the ZenFone 5 with a 5in display and the ZenFone 4 with, you guessed it, a 4in display like the iPhone 5s. Read on to find out what we thought of the budget baby of the line-up in our ZenFone 4 review.See also:Best smartphones 2014
Asus ZenFone 4 review: Price & availability
The ZenFone range was originally unveiled during CES 2014 in January, but have only just been introduced to the UK. The ZenFone 4 is available to order from Asus now for a bargain £99.
We really like the sleek, sophisticated and not overly plasticky look of the ZenFone 5 and 6, but compared with those bigger smartphones the ZenFone 4 looks like a chubby cousin rather than an equally slim and eye-pleasing sibling. It's not ugly, by any means, but it certainly looks chunky despite its smaller screen.
That 4in screen does mean that you can reach its entirety even when using the device with one hand, which will definitely appeal to some.
It's 11.2mm thick, compared with the 9.9mm of the ZenFone 6, the 10.34mm of the ZenFone 5, and weighs 115g so that's nice and light.
Like its bigger counterparts, the ZenFone has a plastic back with a ceramic coating that creates a soft matt finish. We really like the look of the back case, aside from its tendency to pick up fingerprints and other marks. There are several back cases available to choose from if you decide you want to change the colour of your smartphone: Charcoal Black, Pear White, Cherry Red, Sky Blue or Solar Yellow.
It's quite difficult to get that back case off, and you'll need to remove it even if you don't want to change the colour, as you'll find the SIM slot and the MicroSD card slot there too.
It's a shame that the buttons at the bottom of the display don't have a backlight, as it's tricky to know which one you're hitting when you're in a dark environment.
Asus ZenFone 4 review: Display
The ZenFone 4's 4in screen is a 480 x 800 TFT display, making it 233ppi. It's not the worst screen we've seen on a budget smartphone, but it certainly isn't anything special. Viewing angles are acceptable, but overall it's far from a sharp and bright display. We noticed that the display seems to be set back from the actual glass, too, which definitely highlights the budget price of this smartphone.
Asus does include its Splendid app as one of the stock apps on the ZenFone 4 though, so you can fiddle about with the display settings and adjust it to suit you better.
Asus Zenfone 4 review: Hardware & performance
Inside the ZenFone 4 is a dual-core 1.2GHz Intel Atom Z2520 processor paired with 1GB of RAm, which we found to be quite zippy for such a cheap smartphone. We didn't experience any painful lag, but we wouldn't go so far as to say that it's lightning quick.
Taking a closer look at the ZenFone 4's performance, we found that it performed surprisingly well in the Graphics test we carried out using GFXBench. It managed to score an average of 16.5fps in the T-Rex test, which is actually higher than its larger siblings.
When it comes to overall performance, though, the Geekbench 3.0 results were much less impressive, but more in line with what we'd expect from a budget smartphone like this one. In the single core test, the ZenFone 4 scored an average of 338 and 805 in the multi-core test, which is much slower than the other ZenFones.
The single-core results are quite similar to the Motorola Moto G 2014 and the £99 EE Kestrel, but the multi-core results are lower than both of those budget smartphones, closer to the Motorola Moto E and HTC Desire 500.
The ZenFone 4 also scored quite badly in the SunSpider web browser test. It scored 1363ms, which is actually better than the Motorola Moto G 2014, but slower than the likes of the EE Kestrel and the Samsung Galaxy S5 mini.
The rest of the ZenFone 4's specs are quite good for its £99 price tag. It comes with just 8GB of internal storage, which can be expanded up to 64GB thanks to the microSD slot.
It offers 802.11 b/g/n WiFi and Bluetooth 4.0, but there's no NFC or IR Blaster, as can be expected from a smartphone at this price. There's no 4G, either, which is a bit of a shame as that's a huge selling point of the equally priced EE Kestrel.
Asus ZenFone 4 review: Cameras
The camera on the back of the ZenFone 4 is 5Mp, and certainly isn't anything to shout about. It's ok for taking the odd snap here and there, but if you're intending to use your smartphone as your sole camera on holiday, for example, you'll probably want to look elsewhere.
On the front is a quite terrible 0.3Mp camera, so it's unlikely you'll want to take many photos with that one.
We do really like Asus's Camera app, though. It comes with lots of filters and effects that can help disguise the otherwise undesirable quality of the photos, including HDR, Depth of Field, Panorama, Miniature, Portrait and more.
Asus ZenFone 4 review: Software
In addition to that brilliant camera app, we also love lots of other elements of Asus's ZenUI interface, which has bold colours, a flat design and simple navigation that makes it a pleasure to use. It's based on Google's Android 4.3 Jelly Bean, though, so it's not the most up-to-date version of the operating system.
Asus's own apps that come pre-installed on the ZenFone 4 include What's Next for managing your schedule and Do It Later for keeping track of your to-do list, both of which we found to be very useful.
Asus ZenFone 4 review: Battery life
The ZenFone 4's battery life is good, but it's no where near as impressive as the ZenFone 5 and ZenFone 6's, which we found to be exceptional. You can expect to get a day's use out of the ZenFone 4.
There is a Power Saver app that can help you get more out of the ZenFone 4's battery though. We used Optimised mode and Smart Saving, which make some small changes to the ZenFone such as the brightness levels to prolong battery life, but there's also an Ultra-Saving mode that will disconnect the ZenFone from the network when it's locked so you won't immediately get notifications from messaging apps that use the internet, for example.
Buying Advice For £99, we're impressed by the ZenFone 4. It's nicely designed, has brilliant software features, is suitably speedy and has decent battery life, but it's not outstanding. We'd like to see a slightly better camera and the addition of 4G connectivity.
We'd suggest checking out the EE Kestrel and the Motorola Moto G 2014 as alternatives to the ZenFone 4, but it's certainly a worthy contender and we think you'll be satisfied if you decide to go with this good budget smartphone.