Display and Touch
The Zenfone 2 features a 5.5-inch IPS LCD display with 1920×1080 resolution (408 ppi), and it looks excellent. ASUS points out that this phone's design offers a 5.5-inch display in the body of a typical 5-inch device, and the 72% screen-to-body ratio does translate into a larger-screened device that is surprisingly easy to hold and use with one hand.
The Zenfone 2 produces very sharp text and good color from its IPS LCD panel, which I left in the default "balanced" mode. There are three different viewing modes (vivid, reading, and balanced) to choose from, and you can customize the color saturation and hue to fine tune the screen to your liking. When compared to an AMOLED phone display then Zenfone 2 does look washed out and considerably less vivid, but pentile pattern screens such as the AMOLED panel in the Nexus 6 are providing greater vibrance with less accurate color overall. Of course in the end it will be a matter of personal preference as to which looks better.
To give a quick example of the out-of-box difference between an AMOLED and IPS display here's the Nexus 6 (top) vs. the Zenfone 2 (bottom) displaying the same image, both phones set to 50% brightness.
Nexus 6 (top) exhibits greater contrast and saturation compared to Zenfone 2 (bottom)
While the Nexus certainly offers more "pop" which will appeal to many people, it is interesting to see how these displays compare when measured for accuracy.
Zenfone 2 CIE Diagram (white outline)
Testing the display using a Spyder4Pro colorimeter with HCFR show a fairly accurate result (RGB result is the white outline). The display does look slightly cool, though color is considerably more accurate than most AMOLED panels, an inherent advantage of the IPS technology (which has a red, green, and blue sub-pixel pattern for each display pixel). This difference is obvious when looking at the Nexus 6 result:
Nexus 6 CIE Diagram (white outline)
Here we see the huge exaggeration of green reproduction with the pentile display in the Nexus 6, and an overall slightly oversaturated result. The biggest advantage of AMOLED is the unbeatable black level performance, which is essentially 0% light output as the subpixels are producing the light (there is no LED backlight with this technology). I have found the inaccurate color from most AMOLED screens to be less significant in daily use as my eyes adjusted to the green level, though I find pentile to provide less clarity with fine text, even at higher resolution. In any case the IPS panel in the Zenfone 2 provided crisp text with a screen that was very sharp without any edge enhancement evident.
Overall the Zenfone 2 is one of the better IPS displays I've seen on an Android phone, though not quite up to the quality of an iPhone panel. Still, we're talking about the display on a phone you can buy for $199 (both models use the same screen), which is really amazing compared to what most budget phones have to offer.
Just as important as the display quality is the touchscreen, and in this case we have an outstanding digitizer implementation that rivals the best I’ve ever used (iPhone). With sensitivity and precision as high as it was with this Zenfone 2, it feels like there must have been some hardware optimization done at the OS level – and that’s a very good thing. ASUS lists the response time for touch input as 60 ms, and in my use it was very responsive – significantly better than the Nexus 6, which is my daily driver.
Not only did touch seem to respond instantaneously, but it handled speed and acceleration extremely well – so much so that after the Zenfone my Nexus 6 felt downright sluggish.
One of the biggest changes from the stock android experience I'm used to from my Nexus 6 came via gestures, and the Zenfone 2 offers several gestures including different ways to wake and sleep the phone. This helped mitigate the problem with the hardware sleep/wake button, which is rather inconveniently located on the top center, difficult to reach one-handed. However after a couple of days with the phone I completely stopped using this button as it was easier to simply tap the screen instead.
Two taps on the screen will awaken the Zenfone and two more on the status bar at the top of the screen will put it to sleep again. It became second nature to operate the phone this way after a couple of weeks, and I later found myself trying to do it with my Nexus 6 (to no avail).