ASUS ZenFone 4 Pro Review: The Best ZenFone Ever

ASUS's glass smartphone is fragile yet powerful, with a long-lasting battery. 

ASUS's ZenFone lineup has always been a pretty popular line, but not in the US. The ZenFone 2 and 3 lineups were very popular over in Asia and European markets, and now ASUS has launched the fourth generation of its ZenFone. As usual, there are a few ZenFone 4 models out there, but the main ones are the ZenFone 4 and ZenFone 4 Pro which are the highest-end models, and also the most expensive. The ASUS ZenFone 4 Pro has a price tag of $599, which puts it in competition with quite a few other unlocked smartphones out there, like the OnePlus 5T and the Essential PH-1. But which one would give you the best bang for your buck? Let's find out in our ZenFone 4 Pro review.

Specs

ASUS has put a 5.5-inch 1920 x 1080 resolution AMOLED display on the ZenFone 4 Pro, which gives it a pixel density of 401 ppi. It is covered in Gorilla Glass 5 for protection. There's a Snapdragon 835 under the hood, which is paired with the Adreno GPU and 6GB of RAM. There are two storage options here, 64GB and 128GB. There is also a microSD card slot that supports (theoretically) up to 2TB of storage, but there are only microSD cards available right now up to 400GB. So there's still plenty of space for most people here. This is powered by a 3600mAh battery along with Android 7.1.1 Nougat running out of the box. It will get Android Oreo, according to ASUS, but there's no firm date for that release just yet.

For camera optics, there's a dual-camera setup on the back. There's a 12-megapixel main sensor with an f/1.7 aperture, and then a 16-megapixel secondary, telephoto lens. The main lens has optical image stabilization on 4-axis, phase detection autofocus and laser autofocus. The front-facing camera here is an 8-megapixel sensor with a f/2.2 aperture. And like the Pixel 2, the ZenFone 4 Pro has Portrait mode on both the rear and front-facing cameras. As far as other connectivity goes, we have WiFi 802.11 a/b/g/n/ac, Bluetooth 5.0, NFC, GPS with A-GPS, GLONASS, BDS, and GALILEO and there is also a headphone jack here. Finally, ASUS is using a USB-C port for connectivity here.

In the Box

When it comes to the unboxing experience, we usually don't talk about how it was packaged, but ASUS packaged the ZenFone 4 Pro rather uniquely. When you open the box, you don't see anything but a bunch of boxes inside. That is because the phone actually folds out in another compartment. Which is a rather cool way to package it, but perhaps more importantly, it means that when you open the box, it's less likely that the phone will fall out and land on the ground. Definitely important since it is all glass. On the left side, there is another box which has a folder of paperwork, the SIM ejection tool, your USB-C/USB-A adapter, and a pair of headphones. There is also a wall adapter inside, which does not support Quick Charge 3.0, but it does do 2A which is comparable to Quick Charge 2.0. Beneath the phone's compartment, there is another box that has the TPU case for the ZenFone 4 Pro. ASUS is one of the very few smartphone makers to also include a case with their phone, and that's definitely appreciated.

Hardware & Build

ASUS isn't really known for its build quality, at least not in the mobile space, whereas its laptops are another story. But the ZenFone 4 Pro might be the best-built ZenFone it has ever made. It's a full-glass smartphone with some metal on the frame (and yes, antenna lines are still here). And while a glass build does make it much more fragile, it does make it look really nice and premium. Of course, the other side of that double-edged sword is that the ZenFone 4 Pro catches fingerprints like crazy.

The ZenFone 4 Pro comes in two colors, there's Moonlight White and Pure Black. The model that we have in our hands is the Pure Black model and well, it doesn't really look that black. The front and the sides look more like a dark gray, with the back actually looking like a navy blue. Now, this is all based on the lighting that you look at the phone in, but it does look good. The back of the ZenFone 4 Pro is pretty clean. There's the dual-camera module in the upper left-hand corner, with the flash next to it, and then the logo in the middle of the back. And that's it. The camera does still have a bump, although it is very small, so it's a little puzzling that it actually still exists since this the bump is much smaller than in previous models.

ASUS has the volume rocker and power button on the right side of the phone, with the USB-C port, 3.5mm headphone jack, and speaker at the bottom. Unfortunately, ASUS is only using one speaker here, and not doubling the earpiece as the second speaker like most other manufacturers right now. The left side houses the SIM and microSD card slot. The front of the phone, despite having some rather large bezels, is actually pretty clean as well. There is a physical home button on the front that doubles as a fingerprint sensor, and then there are capacitive buttons on either side of the home button. These capacitive buttons actually disappear so you don't really ever see them, resulting in a pretty clean look overall here. At the top, there is the earpiece which is where you'll find the LED notification light, and of course, your usual sensors are up there along with that 8-megapixel front-facing shooter.

By today's standards, the ASUS ZenFone 4 Pro is actually a fairly large device compared to its screen size. But it does feel rather nice in the hand, thanks to the glass. Now, the one thing that ASUS could improve on here is making the back curved a bit. The subtle curves really make a phone feel better in the hand, and keeps it in your hand instead of sliding out. Which is important when you have a glass-backed device. Glass is slippery and fragile, which are definitely two things you usually don't want in a smartphone, but that is where the industry is going right now.

Display

While most manufacturers are going with a taller display panel this year, adopting the 18:9 (really the 2:1) aspect ratio and going with super small bezels, ASUS decided not to do that with the ZenFone 4 Pro. Instead, we have a traditional 16:9 aspect ratio display here, measuring in at 5.5 inches diagonally. Now, this is an AMOLED panel, which is a nice change for ASUS, ditching the IPS of the past ZenFone models. An AMOLED panel traditionally has deeper blacks and more saturation than other display panels, but it is also better on battery life since it lights up individual pixels instead of the full display. Meaning a black wallpaper can really save some battery life for you.

This AMOLED panel actually looks really good. Since it's an AMOLED panel, that means it is a Samsung OLED panel and not an LG panel. So you won't need to worry about any of the Pixel 2 issues cropping up here. The blacks on this panel are nice and deep as you'd expect, and the colors are just a bit saturated. It's not overdone, but it's definitely not "natural". ASUS does, however, have a few different color modes that you can choose from on the ZenFone 4 Pro. This includes Super Color, Bluelight Filter, Standard and then Customized. With the "Customized" option, you have the ability to not just adjust the temperature (that is available on other modes too), but also the Hue and Saturation. During this review, we left the Super Color option on, since it's the default, it is the one that most people will be using here.

As far as brightness goes, it's pretty darn good. It gets bright enough for you to use outside in direct sunlight, but it's not quite as bright as something like the Galaxy S8 or Galaxy Note 8. And that's not an issue, and also not a surprise, since virtually no other smartphone has 1000 nits of brightness. Since this is an AMOLED panel, ASUS was able to add in an Always On Display feature here. It's rather limited but works just like you'd expect. There are a few different clock faces available in the settings, and it'll show you the date and time, as well as any missed calls, texts and the battery percentage. To avoid burn-in, Always On Display does move the image that is on the display every so often. So sometimes you may see the clock at the top of the display, other times it might be in the middle or at the bottom.

Performance

On paper, the ASUS ZenFone 4 Pro is right up there as being one of the most powerful Android smartphones on the market right now. But as we know all too well, software makes a huge difference in how a smartphone performs, it can really slow it down. However, that is not the case with the ZenFone 4 Pro. The Qualcomm Snapdragon 835 inside is a beast, as it has shown in numerous other flagships launched already this year. Paired with the Adreno 540 GPU and 6GB of RAM, it's a great experience using this smartphone. The ZenFone 4 Pro never really slowed down, and it never felt like it was being throttled (usually this is due to heat). That's definitely a good thing, considering some smartphones have made the Snapdragon 835 look sluggish and get fairly warm. Now, don't get me wrong, the ZenFone 4 Pro can get hot like most smartphones when you are gaming on the phone, but for the most part, there are no issues here.

There's 64GB of storage on-board on our review unit here, and that seems to be the new entry level for premium storage in 2017, and that's a good thing. 64GB of storage leaves you with around 53-54GB of available storage which is plenty for most people, and of course, if it isn't, you can also throw in a microSD card and get more.

Sound

The ASUS ZenFone 4 Pro is one of the very few flagships to launch in 2017 and still have a headphone jack. And many people will applaud ASUS for keeping the headphone jack intact. But unfortunately, ASUS didn't take LG's route of putting in a quad-DAC in the ZenFone 4 Pro. So depending on the headphones you have plugged in, the audio quality is pretty average. The included headphones are actually fairly decent, for included headphones. Just don't expect them to blow you away. Now the speaker is at the bottom of the ZenFone 4 Pro, to the right of the USB-C jack. The speaker is pretty loud and has an "Outdoor Mode" that ASUS has had in its smartphones for quite a while now. So it does get really loud, but it's not necessarily that impressive. There is DTS Sound Studio inside the ZenFone 4 Pro, so you can adjust the sound, and when you put it on "Pop" it sounds a bit tinny. Though if you don't adjust the settings, it'll sound just fine. Just make sure you don't put your finger on the speaker when playing games and such.

Fingerprint Sensor

The fingerprint sensor on the ZenFone 4 Pro is also the home button, and to no surprise, it's fast and accurate. I can't count the number of times I've said that in a review about a smartphone this year. It's a pretty common trend at this point, and that's a good thing, actually. The sensor does vibrate subtly when it recognizes your fingerprint, but like other home buttons, you don't actually press it, just touch it, like a capacitive button. It's not a big deal here, but it would be nicer to physically press the button and only touch it to go home. It still works just fine though.

Phone Calls & Network

The ZenFone 4 Pro is an unlocked smartphone from ASUS, and it will work on GSM networks. During the review process, we used the ZenFone 4 Pro on T-Mobile here in the US. It worked perfectly fine on T-Mobile's 4G LTE network, with speeds comparable to what we've gotten on other smartphones on the same network. Phone calls were also perfectly fine. Users on the other end were able to hear us without any issues. However, it is worth noting that the ZenFone 4 Pro does not support HD Voice, VoLTE or WiFi Calling, so you'll want to keep that in mind if you are looking to pick up this smartphone.

Benchmarks

For benchmarking, we did run the usual three benchmarks on the ZenFone 4 Pro. That includes AnTuTu, 3D Mark and Geekbench 4. For AnTuTu, it picked up a score of 165,826. That was good enough to keep it in the pack of other Snapdragon 835 devices on the rankings. For 3D Mark, it grabbed a score of 3723. Finally, over on Geekbench 4, it picked up a single-core score of 1900 and a multi-core score of 6210. You can see the full results from the testing in the gallery below.

Battery Life

The battery on the ZenFone 4 Pro is pretty impressive, actually. There is a 3600mAh battery pack inside, which is powering the 5.5-inch full HD display here, and it lasts all day and then some. In fact, we were not able to kill the battery in one day, we typically had to wait until the next day. The battery is really impressive. We got nearly 6 hours of on-screen time, even with YouTube using up a ton of juice during this particular cycle. This also included some gameplay, as well as surfing the usual apps like Twitter, Instagram, and such. So for most people, the ZenFone 4 Pro is going to last you a full day, even if you are a heavy user.

Of course, if for some reason the battery doesn't last you all day long, there is Quick Charge 3.0 support included here, though you'll need to get another charger to take advantage of it. Still, with Quick Charge 3.0, you are able to charge up to 80% in about 35 minutes. Allowing you to quickly top off your battery after a long day at work, before heading out for some drinks in the evening. Going from o to 100% on the ZenFone 4 Pro takes roughly about an hour and a half, using Quick Charge 3.0, which is about the normal rate for a battery this size.

Software

As of this writing, the ZenFone 4 Pro was running on Android 7.1.1 Nougat and had the October 1st, 2017 security patch. That's a fairly recent security patch, and ASUS does plan to bring Android 8.0 Oreo to the ZenFone 4 Pro in the future, but the exact timing was not shared.

The software on the ZenFone 4 Pro is exactly what you'd expect from an ASUS smartphone. It's running on ASUS' custom software that overlays Android 7.1.1 Nougat. The software hasn't changed a whole lot in recent years, it's still a rather bright interface (as the background is all in white), but does offer some rather nifty features. One of the features that's pretty interesting here is OptiFlex. This is an option in the settings, where the user can choose which apps it wants to launch faster. ASUS can actually auto-determine which ones to launch faster based on your usage. So those that you use more, it'll automatically launch faster, but you can also pick and choose as well. This is actually something you'll notice when using the phone. OptiFlex does launch apps much faster than on other smartphones, even with the same hardware. And while it could be a placebo effect (from shortening animation times and such), it is a pretty nice feature to have here.

In the notification shade, you'll notice a good number of toggles that you can flip on and off, but there's also a calculator in there. This is a really nifty feature to have on the ZenFone 4 Pro. Since you can simply pull down the shade and then open the calculator, rather than going home, jumping into the app drawer and opening the calculator if you need it. It definitely doesn't sound like a big deal, but in everyday usage, it is a pretty big deal.

The software on the ZenFone 4 Pro does run very smoothly, something you would obviously expect from a smartphone running with the Snapdragon 835 and 6GB of RAM, but still nice to see. Speaking of RAM, we always had at least a full gigabyte of RAM free, so if you are deciding between the ZenFone 4 Pro or the ZenFone 4 which is $100 cheaper, the main differences between the two is the extra RAM in the ZenFone 4 Pro. So the ZenFone 4 would still be a great choice since the two are basically the same otherwise.

Camera

Over the years, ASUS has made some good cameras, it hasn't made impressive cameras like the Google Pixel or the Galaxy S8, but cameras that get the job done. It's basically been stuck in the middle ground, as far as cameras go. Now ASUS made the jump over to dual cameras last year with the ZenFone 3 Zoom, and now it's here on the ZenFone 4 Pro. It features a 12-megapixel main sensor and then a 16-megapixel secondary, telephoto sensor. This is actually a bit of an interesting setup, since the telephoto lens and/or the secondary lens, usually has a lower megapixel count then the main lens. But it appears to work really well, the way that ASUS has it set up here.

In the camera app, you can switch between 1x and 2x zoom without really noticing any differences in the picture quality. That is because it is just switching between the two cameras. But when you use the 5x zoom in the camera app, you will see a big difference, and usually see a lot more noise, depending on the lighting. Not the most ideal setting, but it is nice to have at your disposal, should you need it. For most people, 2x zoom is going to be more than enough for most things. ASUS does have a number of modes included with its camera app. Unlike some other smartphone makers, ASUS hasn't gone too crazy with the number of modes on this one, but it has added a decent amount to keep users happy. There is of course auto and manual modes, so you can get the perfect shot, no matter the condition. There is also beauty, super-resolution, GIF animation, panorama, slow motion and time-lapse. Super-resolution is basically what it sounds like, it produces much larger images, with a resolution of 7832x5872, versus the regular 3916x2936. This gives you the same size image as a 46-megapixel camera, but with a much smaller file size. Throughout our testing, we haven't really seen this add any benefit, other than when in already well-lit conditions. It doesn't really do well in low-light conditions, unfortunately.

The actual photos from the camera on the ZenFone 4 Pro are actually really good. They offer up a tad of saturation, but not a lot, just enough to keep you happy. They also don't appear to over-expose in most conditions, where other cameras will tend to over-expose, especially in the background. The camera is also pretty good in low-light conditions, even with different colors in the background for lighting, as is the case with the photo in the gallery below of the Android figurine from Google I/O, there are a lot of different colors in the background, but it still worked out pretty well.

Now, the front-facing camera has a feature that really only the Google Pixel 2 has (at least on the Android side of things) right now. And that is indeed the portrait mode. On the rear-facing camera, it's actually called depth effect, but it is basically a macro or portrait mode feature. It works pretty well on the front-facing camera as well. It appears to be able to do really well at determining the subject and only blurring the background. Some smartphones will blurry the sides of a face as they have trouble determining the foreground from the background, but that's not the case here, and that's great to see. You can see some examples in the gallery below.

The Good

Build Quality

Camera

Battery Life

Display

Headphone Jack

NFC

The Bad

Outdated Version of Android

Very Slippery Glass Back

Wrap-Up

The ZenFone 4 Pro is a pretty impressive smartphone from ASUS. It's genuinely hard to find anything to complain about the ZenFone 4 Pro here. It checks most boxes, including having a great camera, a great display, and great battery life. The only real downside is the availability of the ZenFone 4 Pro. Unfortunately, it is only sold in the US unlocked, which means it won't get into a lot of hands, and it only works on GSM networks as well.

Should I buy the ASUS ZenFone 4 Pro?

If you're on a GSM carrier like T-Mobile or AT&T, definitely. The ZenFone 4 Pro is a great device to pick up. It is truly one of the best smartphones ASUS has ever made. While it is missing a few carrier features like HD Voice, WiFi Calling, and VoLTE, those aren't really mainstream yet, so that shouldn't be a reason not to pick up the ZenFone 4 Pro right now.

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About the Author
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Alexander Maxham

Section Editor
Alex has written for Androidheadlines since 2012 as Editor of the site and traveled the World to many of the biggest Smartphone and Technology events. Alex has a background in Technology and IT and Deep Passion for Everything Android and Google. His specialties lay in Smartphones of all budgets, Accessories, Home Automation and more. Contact him at [email protected]
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