The ZUK Z1 has a 5.5" 1080p screen, which under Chinese influence has been turning into the the new golden midrange standard. At 401ppi the screen is sharp and doesn't tax the chipset or the battery like QHD would have.
Resolution aside, ZUK did plenty to optimize image quality. We measured the screen at 396 nits and a contrast of about 1,000:1, which is average.
Display test
50% brightness
100% brightness
Black, cd/m2
White, cd/m2
Contrast ratio
Black, cd/m2
White, cd/m2
Contrast ratio
ZUK Z1 by Lenovo
0.21
205
981
0.39
396
1021
Lenovo K3 Note
0.13
230
1742
0.24
432
1793
OnePlus Two
0.16
180
1139
0.30
399
1334
Meizu MX5
0.00
117
∞
0
346.00
∞
Xiaomi Redmi Note 2
0.17
162
953
0.492
467.00
953
An Outdoor mode (which can be triggered automatically) changes the screen settings, allegedly to make the screen more legible in the sun. We appreciate the hardware solution more - a polarizing filter that further improves legibility (similar to the ClearBlack tech we've seen on Lumias).
Sunlight contrast ratio
Nokia 808 PureView 4.698
Samsung Galaxy S6 edge+ 4.615
Samsung Galaxy E7 4.485
Samsung Galaxy A3 4.241
Samsung Galaxy S6 edge 4.124
Samsung Galaxy S6 4.124
Samsung Galaxy Note5 4.09
Samsung Galaxy Note 4 4.033
Apple iPhone 5 3.997
Samsung Galaxy Note 3 3.997
Samsung Galaxy A5 3.895
Samsung Galaxy J7 outdoor 3.879
Samsung Galaxy A8 3.859
Apple iPhone 6 3.838
Motorola Moto X (2014) 3.816
Samsung Galaxy Note Edge 3.799
Apple iPhone 6s 3.783
Vivo X5Pro 3.706
Samsung Galaxy A7 3.679
Oppo R5 3.678
Samsung Galaxy K zoom 3.675
Nokia Lumia 930 3.567
Apple iPhone 5s 3.565
Samsung Galaxy S5 3.549
Nokia Lumia 735 3.547
Motorola Nexus 6 3.543
Apple iPhone 6s Plus 3.53
Alcatel Idol X+ 3.527
Apple iPhone 5c 3.512
Samsung Galaxy Alpha 3.509
Oppo R7 Plus 3.499
Samsung Galaxy Note 3 Neo 3.487
vivo X5Max 3.472
LG G Flex2 3.465
YotaPhone 2 3.453
Samsung Galaxy J7 3.422
Motorola RAZR MAXX 3.42
Samsung I9300 Galaxy S III 3.419
Meizu MX5 3.416
Samsung Galaxy S5 Active 3.406
Nokia Lumia 925 3.402
Gionee Elife S5.5 3.386
Samsung I9505 Galaxy S4 3.352
Oppo R7 3.32
Samsung Omnia W 3.301
Samsung Galaxy S5 mini 3.174
Samsung I9000 Galaxy S 3.155
Samsung Ativ S 3.129
Samsung I9190 Galaxy S4 mini 3.127
Samsung Galaxy S4 zoom 3.118
Nokia N9 3.069
Microsoft Lumia 640 XL 3.065
Apple iPhone 6 Plus 3.023
Samsung Galaxy Note 2.97
Samsung Galaxy Premier 2.958
Sony Xperia Z1 2.95
HTC One S 2.901
Lenovo S90 Sisley 2.892
Samsung I8730 Galaxy Express 2.861
BlackBerry Q10 2.856
Samsung I9100 Galaxy S II 2.832
Sony Xperia Z3+ 2.824
HTC Desire Eye 2.815
Gionee Elife S5.1 2.812
Samsung Galaxy S II Plus 2.801
BlackBerry Z30 2.79
Sony Xperia Z5 compact 2.784
Meizu MX4 Pro 2.765
Sony Xperia M5 2.69
Sony Xperia ZR 2.672
Huawei Ascend P1 2.655
Xiaomi Mi 4i 2.641
Sony Xperia Z3 2.618
Sony Xperia Z3 Compact 2.616
Sony Xperia T3 2.609
BlackBerry Passport 2.595
Microsoft Lumia 640 2.563
Nokia Lumia 900 2.562
Motorola Moto G 4G 2.546
HTC One Max 2.537
Nokia Lumia 720 2.512
HTC One 2.504
Sony Xperia M4 Aqua 2.503
Motorola Moto G 2.477
vivo Xshot 2.465
Sony Xperia Z 2.462
Xiaomi Mi 4 2.424
Samsung Galaxy S III mini 2.422
Lenovo Vibe Z2 Pro 2.416
LG G Flex 2.407
Huawei Honor 7 2.406
ZUK Z1 by Lenovo 2.382
HTC Desire 820 2.372
HTC One (M8) 2.371
Meizu MX4 2.366
Motorola RAZR i 2.366
Meizu m1 note 2.362
Sony Xperia ZL 2.352
HTC One M9 2.334
LG G4 2.317
Samsung Galaxy Note II 2.307
HTC One E9+ 2.305
HTC One (M8) for Windows 2.291
Oppo R1x 2.281
Oppo Find 7a 2.279
Alcatel One Touch Hero 2.272
Apple iPhone 4S 2.269
HTC Desire 600 dual sim 2.262
Sony Xperia C5 Ultra 2.253
Nokia Asha 311 2.25
Sony Xperia C4 Dual 2.235
Xiaomi Mi Note 2.234
Motorola Moto G (2014) 2.233
LG Nexus 5 2.228
Huawei P8 2.196
Nokia Lumia 820 2.193
HTC One (E8) 2.185
Oppo N3 2.181
Nokia Lumia 920 2.17
Huawei Honor 6 2.169
Xiaomi Redmi Note 2 2.166
OnePlus Two 2.165
HTC One X 2.158
Asus Zenfone 2 ZE551ML 2.149
LG Aka 2.145
Nokia N8 2.144
Nokia Lumia 620 2.142
Nokia 515 2.134
Archos 50 Diamond 2.134
HTC Desire 500 2.129
Sony Xperia C3 Dual 2.12
Xiaomi Redmi Note 2.119
Sony Xperia acro S 2.119
Nokia Lumia 1020 2.103
Oppo Find 5 2.088
Sony Xperia SL 2.078
Huawei P8lite 2.078
Nokia Lumia 630 2.056
BlackBerry Z10 2.051
Moto G 3rd gen max manual 2.026
Huawei Ascend Mate7 2.024
Samsung I9295 Galaxy S4 Active 2.022
Apple iPhone 4 2.016
HTC One mini 2.003
Xiaomi Mi 3 2.001
Huawei Ascend P7 1.992
LG G2 1.976
Sony Xperia E4g 1.972
OnePlus One 1.961
Oppo R819 1.957
Sony Ericsson Xperia ray 1.955
Lenovo Vibe X2 1.952
Sony Xperia Z2 1.944
Sony Xperia E3 1.943
Nokia Lumia 1320 1.941
HTC One mini 2 1.94
Samsung Galaxy Camera 1.938
Samsung Galaxy Grand Prime 1.935
Sony Xperia J 1.932
Acer CloudMobile S500 1.931
ZTE Blade S6 1.927
LG Nexus 4 1.926
LG G Pro 2 1.922
Samsung Galaxy Mega 6.3 1.913
Nokia Asha 308 1.911
HTC Butterfly 2 1.905
Sony Xperia T 1.894
Meizu m2 note 1.892
BlackBerry Leap 1.892
Nokia Lumia 830 1.887
HTC Desire X 1.878
HTC Windows Phone 8X 1.873
HTC Butterfly 1.873
HTC Butterfly S 1.867
Huawei Ascend P6 1.865
Huawei Ascend Mate 1.845
LG G2 mini 1.838
LG G3 1.82
Nokia Lumia 1520 1.813
HTC Desire 616 dual sim 1.797
Sony Xperia V 1.792
HTC Desire 816 1.783
Sony Xperia Z1 Compact 1.772
HTC Desire 700 dual sim 1.769
ZTE Nubia Z9 mini 1.759
Sony Xperia U 1.758
Meizu MX3 1.754
LG Optimus G 1.753
Sony Xperia T2 Ultra 1.74
Sony Xperia Z3 Tablet Compact 1.735
Acer Liquid Jade S 1.734
Sony Xperia SP 1.733
Oppo Find 7 1.691
LG Optimus 4X HD 1.691
HTC One V 1.685
BlackBerry Q5 1.682
LG Optimus Vu 1.68
Motorola Moto E (2nd Gen) 1.675
Xiaomi Mi Pad 7.9 1.672
LG Optimus GJ 1.666
ZTE Nubia Z9 1.659
LG Optimus 3D Max 1.658
HTC Desire V 1.646
Samsung Galaxy Xcover 2 1.632
Samsung Galaxy Ace 3 1.622
Microsoft Lumia 532 1.615
Jolla Jolla 1.605
Microsoft Lumia 435 1.598
Sony Xperia Z Ultra 1.578
Sony Xperia go 1.577
Samsung Galaxy Ace 2 I8160 1.566
Samsung Galaxy Core 1.563
LG Optimus G Pro 1.552
Motorola Moto E 1.545
LG Optimus 3D 1.542
Nokia Asha 302 1.537
Samsung Galaxy Core Prime 1.507
BlackBerry Curve 9320 1.488
Sony Xperia M 1.473
Oppo N1 1.47
Sony Xperia E4 1.467
Meizu MX 4-core 1.462
Nokia Lumia 610 1.432
Samsung Galaxy S Duos 1.4
Samsung Galaxy Grand Neo 1.393
Sony Xperia M2 1.393
Microsoft Lumia 535 1.393
Samsung Galaxy Grand 2 1.38
Sony Xperia E1 1.372
Nokia Lumia 625 1.371
Gigabyte GSmart G1355 1.361
Sony Xperia L 1.351
Xiaomi Redmi 1S 1.35
Samsung Galaxy Mega 5.8 1.35
HTC Desire 510 1.34
Sony Xperia M2 Aqua 1.331
Sony Xperia miro 1.324
Samsung I9082 Galaxy Grand 1.321
Samsung I8530 Galaxy Beam 1.315
Xiaomi Redmi 2 1.311
HTC Desire C 1.3
Nokia X 1.291
Sony Xperia C 1.283
Nokia Asha 503 1.281
Nokia Asha 501 1.27
LG Optimus L7 1.269
Nokia Lumia 510 1.268
Samsung Galaxy Fame 1.245
LG Optimus L9 1.227
Meizu MX 1.221
Samsung Galaxy Young 1.22
Sony Xperia E 1.215
Nokia XL 1.204
Sony Xperia E dual 1.203
Asus Memo Pad 7 ME176C 1.198
Samsung Galaxy Pocket 1.18
Nokia Asha 305 1.178
Nokia Asha 306 1.175
Sony Xperia neo L 1.169
Sony Xperia tipo 1.166
Nokia Lumia 520 1.161
Samsung S6802 Galaxy Ace Duos 1.148
Samsung Galaxy mini 2 1.114
Color rendering is fairly accurate (Avg deltaE 5.2 for the primary colors plus black and white), with white being not as accurate as we would expect. With a deltaE of 9.9, it's on the colder bluish side, but you would hardly notice that unless you get some sort of a reference to compare it side by side.
As usual, display colors are a matter of personal taste and perception so if you don't need calibrated color output, you will probably be quite happy with the color rendition on the Z1.
If you are not happy, Cyanogen OS offers plenty of ways to adjust the screen output. We managed to improve substantially the accuracy of the color rendition by adjusting the color temperature via the LiveDisplay feature from 6500K to 5200K. With this adjustment Avg deltaE went down to 3.8 and the rendition of white became almost perfect. The screen however loses some of its maximum brightness in the process and would only go as high as 383nits with this adjustment.
LiveDisplay lets you create two presets for color temperature - one for use during the day and one for night time. You can switch between day/night manually or have the phone do it automatically.
If you're wondering why, it's medical reports claim looking at blue light in the evening can affect your sleeping cycle. Several studies have confirmed that it reduces melatonin - the hormone responsible for sleep. So you might want to use a warmer light setting (i.e. less blue or smaller temperature reading) at night.
Connectivity
The ZUK Z1 is a dual-SIM, dual-standby phone that can freely roam the globe. It has basic GSM and CDMA connectivity, along with 3G data (again GSM and CDMA) and two flavors of LTE (international and Chinese).
Dual-band Wi-Fi a/b/g/n/ac is supported as is Bluetooth 4.1, however there's no NFC or ANT+. This precludes easy pairing and certain sports trackers. Positioning is handled by a GPS and GLONASS receiver.
The wired connectivity is the more interesting part. USB 3.1 Type C promises up to 5Gbps transfers, up from around 0.5Gbps for USB 2.0. While microUSB 3.0 did not last on mobile devices, Type C is building up popularity.
It doesn't look like ZUK has implemented some of the more advanced features of the standard - e.g. DisplayPort TV out and the 100W power delivery spec - but it definitely has the speed. We ran a couple of benchmarks with the Z1 connected to a USB 2.0 port and a USB 3.1 port and copied over a large file from the SSD on one of our office PCs.
We copied the file over several times to the ZUK Z1, first through a USB 2.0 port and then through a USB 3.0 port. The phone didn't max out either standard, but it ran noticeably faster on USB 3.0, especially when copying from the phone to the computer.
USB 2.0
USB 3.0
Read (phone → PC)
28.9MB/s
62.8MB/s
Write (PC → phone)
19.8MB/s
35.9MB/s
Note: the USB Implementers Forum renamed USB 3.0, which leads to some confusion. What used to be USB 3.0 is now "USB 3.1 Gen 1" while what was supposed to be USB 3.1 is marketed as "USB 3.1 Gen 2." Gen 2 doubles the speed of Gen 1, 10Gbps.
Battery life
The ZUK Z1 has a huge 4,100mAh Li-Ion battery. It's made up of two rectangular batteries stacked on top of each other to better fill in the curved shape of the back. Note that you don't get any special fast-charging solutions, the included 5V/2A charger is fast but will still take a while to fill up the battery.
You've probably heard that lithium batteries don't like being overcharged - leaving them plugged in when they are at 100% reduces their lifespan. The ZUK Z1 has a hardware solution to the problem, which disconnects the battery from the charger and run the phone on electricity from the charger. Other phones do the opposite - disconnect the charger from the battery, drain the battery a bit, charge it back up, which isn't good for the battery either.
With such a big battery, the big results come as no surprise. Talk time hovers around 25 hours, an excellent result (even if we expected more). In the browser test the Z1 came 15 minute short of 11 hours, again a good result without being the best. It lasted longer when playing videos, over 14 hours, which too falls in the great, but not perfect category.
Our proprietary score also includes a standby battery draw test, which is not featured in our test scorecard but is calculated in the total endurance rating.
The battery testing procedure is described in detail in case you're interested in the nitty-gritties. You can also check out our complete battery test table, where you can see how all of the smartphones we've tested will compare under your own typical use.
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