What Apple might do next: Past iPhone updates have introduced improvements to both the camera's hardware and software. It's hard to imagine a new iPhone not following suit, with a more powerful sensor and some editing tricks along the lines of what the company introduced with the 5s. The front-facing camera--long the laggard in the iPhone's photo arsenal--could stand some selfie-inspired improvements as well.
Phones have gotten bigger
What Apple did: The iPhone 5s retained the dimensions of its predecessor, right down to its 4-inch screen. (The iPhone 5c was slightly taller, wider, and thicker and weighed 0.7 ounces more, but it also featured a 4-inch display.) Prior to the iPhone 5's 2012 release, iPhones featured a 3.5-inch screen.
What's happened since: While Apple has held the line on how big phones should be, other device makers haven't shied away from super-sizing their products. The HTC One offers a 5-inch screen; the Galaxy S5's screen checks in at 5.1 inches. And those screens are positively cramped compared to the 5.5- and 5.7-inch screens you'll find on the LG G3 and Galaxy Note 4, respectively. These are not outliers--NPD Group says that large-screen smartphones (ones with screens 4.7 inches or larger) now take up a third of the shelf space for national carriers; that's up from 4 percent just two years ago. Those large smartphones also make up more than a quarter of sales, up from 2 percent in the second quarter of 2012. (Interestingly, NPD says that sales figures are lagging, in part because Apple and its smaller-screened phones continue to enjoy a large slice of the smartphone market.)
What Apple might do next: Rumors point to Apple coming out with different sizes of its next iPhone at Tuesday's press event, though given Apple's reluctance to come out with a product just because everyone else is doing it, expect that any iPhone with a larger screen will have a very specific purpose for sporting one.
Displays have packed in more pixels
What Apple did: The iPhone 4 introduced the world to the Retina Display, and it was an eye-popping experience. Packing in 326 pixels per inch onto your phone's screen, Apple's high-resolution display made on-screen text look like something off a printed page. Apple's wisely stuck with the feature through subsequent iPhone iterations: the 5s offers 1136-by-640-pixel resolution with that same 326 pixels per inch (ppi).
What's happened since: Other phone makers have responded by packing in more pixels. The Galaxy S5 boasts a resolution of 1080-by-1920 with a pixel density of 432 ppi while the HTC One (M8) boasts 441 ppi on a scree with the same resolution. That's nothing compared to the Quad HD display on LG's G3: it features a resolution of 2560-by-1440 and 534 pixels per inch.
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