You can cross another resolution off the smartphone display list:
The third device from the Z5 series is the Xperia Z5 Premium, which includes the 5.5" 4k [3840×2160] screen, a 3,430 mAh battery, and the ability to expand its 32 GB of default internal storage by up to 200 GB through microSD cards. The 4k Triluminos IPS display promises to have a high color gamut, higher contrast and higher sharpness, as well. In the few moments I've spent with it at IFA, the screen did indeed look crystal clear.
[...] Xperia Z5 will launch globally in October this year, while the Xperia Z5 Premium should arrive a month later, in November. Both single-SIM and dual-SIM variants will exist for both models.
Some lucky Sony executive is shoving the Xperia Z5 Premium in his Google Cardboard. Next stop, the world's first 5K (5120×2880) smartphone.
(Score: 2) by takyon on Friday September 04 2015, @05:52PM
http://www.itcexperts.com/wp-content/uploads/Capability-of-the-human-visual-system.pdf [itcexperts.com]
Check out the second-to-last page for a range of estimates.
For VR, which can be applicable to a phone [wikipedia.org], view distance is close and lenses are used. 8K and 16K resolutions are industry targets:
http://arstechnica.com/gaming/2013/09/virtual-perfection-why-8k-resolution-per-eye-isnt-enough-for-perfect-vr/ [arstechnica.com]
http://vrfocus.com/archives/13220/abrash-vr-needs-hit-16k-match-retinal-resolution/ [vrfocus.com]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]