Thanks Meter 3476
Join Date: Jan 2009
Location: Spokane, Washington
It's an optical illusion and the reduction in overall width was accomplished by narrowing the bezel. Based on the below, the display itself is actually marginally wider as well as being taller.
The resolution on the N2 is 720x1280 which means the display is 720 pixels wide by 1,280 pixels tall which is the standard 16:9. The N3 is 1080x1920, also 16:9. The vertical and horizontal increase is exactly equal (33%) which means to hit 5.7" (and the increased resolution) the display expanded proportionately horizontally and vertically. Every 1080x1920 display has the same vertical and horizontal proportions no matter what device it's used in as 16:9 (not counting soft keys) is pretty much standard. The N3 and SGS4 have the same pixel measurements (1080x1920) which explains why the SGS4 is 441PPI and the N3 is 386. They have the same number of pixels but the pixels on the N3 are stretched out to cover the larger sized display which reduces the PPI.
Here's an example of one device that doesn't. The Optimus Vu is 768x1024 (4:3).