HTC's new Droid DNA smartphone has plenty of qualities that make it intriguing. It has a quad-core Snapdragon chipset. It crams a 5-inch display in a body nearly the size of a One X or Galaxy S III. Its Super LCD 3 technology trumps the Super LCD 2 that made the HTC 8x display so lovely. By all accounts it's a wonderful device.
But one thing HTC takes particular pride in is the 1920x1080 display, good for a pixel density of 440 pixels per inch, the highest ever in any handheld consumer device. This should make tech nerds lose their shit, right? Not quite. Welcome to your new favorite meaningless stat: ppi.
The problem with most specs is that beyond a certain point, they fail to be useful. You might remember that when digital cameras first appeared, they left plenty of room for improvement. Part of that improvement involved adding megapixels to the sensor, since getting more detail from the sensor typically involved increasing the dimensions of the image itself. But at some point in the mid-2000s, an increase in megapixels no longer meant it was a surefire sign of improvement. My 5MP camera started taking better pictures than your 10MP shooter. Beyond a certain point, unless you're planning on blowing up your picture to the size of a warehouse wall, megapixels just don't matter.
This same line of thinking manifested itself when contrast ratio became a spec for Plasma and LCD displays (OMG ONE ZILLION TO ONE CONTRAST RATIO)—can't see it, doesn't matter—and is now resurfacing as companies enter the pixel density arms race. Increases in pixel density are going from impressive technical feats to masturbatory experiments for the sake of marketing strategy.
So what do we make of HTC managing to pack a 1920x1080 display in a 5-inch screen? When it comes to tangible user benefits, not much. According to those who toil away in research labs, the human eye can not discern granular detail when it is higher than 300 PPI. Hence Apple's 326 PPI display in the iPhone 4 back in 2010. Yes, some—notably Dr. Raymond Soneira of DisplayMate—have argued that no display will be perfectly "retina" until it has a density of 477 PPI. But others, like University of Utah professor Bryan Jones, dispute the basis of Soneira's reasoning, arguing that from a foot away, displays will actually appear retina when greater than 287 PPI. But even Soneira acknowledeged that the retina effect kicks in when a 300 PPI display is held 18 inches away. You know. Where you hold your phone.
Does increased smartphone resolution help for watching high-def movies? Not really. To really reap the benefit of 1080p video, you need no smaller than a 40-inch display (and ideally one above 50-inches) to notice anything awesome while sitting at a comfortable distance. In fact, to theoretically reap any benefits of 1080p video on your phone, you'd need to be holding it 6-8 inches from your face. No one holds their phone 6-8 inches from their face.
Sure, you can get yourself some added digital real estate with a 1080p smartphone display, but you run the risk of making everything too small to easily view. In fact, the only tangible benefit of a 1080p is that a phone's chipset doesn't then have to waste horsepower scaling down the resolution of high-def content. That's a minor reward, though, one offset by all that pixel-pushing gobbling up hardware resources and battery life.
That's not to say that the Droid DNA has a bad screen by any means. In fact, our own Brent Rose thinks its the best smartphone screen he's ever seen, citing its rich colors, and sharp text. But that more to do with HTC's Super LCD 3 technology and its rendering engines as it does raw pixel density, in the same way that a camera's ISO performance matters far more than its megapixelage.
Does this mean that the display wars are over, and everyone should give up on trying to make better screens? Of course not. There are plenty of ways to make a better-looking display. But we've reached the point in the pixel density wars where higher figures have stopped automatically equating to improved performance for users. Any grandstanding about pixel density, from here on out, now is mostly just marketing fluff.