Why do mobile displays get all the love?


— 9:52 AM on April 6, 2012

With few exceptions, it seems, the gadgets hogging the media limelight today tend to be of the fingerprint-collecting variety. Tablets, phones, tablet-phones, e-readers, and anything else manufacturers can saddle with a media decoding chip and a touchscreen saturate the headlines on a daily basis. Much like during the netbook onslaught of yesteryear, the portion of my brain devoted to caring about such things is reaching full capacity. There is, however, one aspect of these shiny slabs that continues to pique my interest: the displays.

In this regard, mobile devices have become the daddy's girls of the electronics world. Where PCs have to pinch pennies to score a rusty set of wheels when they reach legal driving age, tablets and phones wake up on their 16th birthday with a brand new Mustang convertible in the driveway. In PC land, aspect ratios keep getting squished, cheap panels abound, and accurate color reproduction and contrast are relegated to budget-busting models. Looking at laptops, the situation is even more dire. Apparently, we all missed the board meeting where it was decided that 1366x768 ought to be enough for anybody.

Smaller mobile devices, on the other hand, are going through a display renaissance of sorts. Manufacturers are doing everything they can to increase pixel counts, and vivid panels based on IPS and OLED technology permeate the market. Apple's new iPad introduced the world to a 2048x1536 resolution spread across 9.7" of IPS-fueled liquid crystal goodness, and many Android handsets now stretch 720p resolutions across 4" screens. Despite these advances, here I sit, cruising at 35,000 feet, banging out a blog post on a 12.1" screen with a mere 25% of the new iPad's pixel count.

The average LCD monitor has slowly but surely gained extra color-changing dots over the years. However, the upticks have been somewhat less than dramatic. We've basically just stretched the field of 1024x768 and 1280x1024 monitors into squat, 16:9 panels with 1366x768 and 1920x1080 resolutions. Screen sizes have increased to accommodate the additional pixels, but the number of pixels per inch (PPI) has remained largely unchanged.

In stark contrast, the humble smartphone screen has seen its pixel count skyrocket from 320x240 to as much as 1280x720. That's up to a 12X increase in the number of pixels crammed into displays that have grown perhaps only an inch or two larger. As a result, smartphone screens have managed to ramp up not only their resolution, but also their PPI.

Why does increasing the pixel density matter? Because adding more pixels per unit area makes everything look better, from pictures to icons to text. High-PPI displays are particularly good at smoothing out the jagged edges of fonts, resulting in crisper text that's easier to read. This added fidelity is particularly beneficial to handheld devices equipped with relatively small screens, so it's no wonder smartphones have been the first consumer devices to feature higher pixel densities. But why are smartphone and tablet panels advancing at such a breakneck pace while I can still count the individual pixels on my laptop?

If I were a betting man, I'd drop my hard earned dough on the theory that, at a given density, smaller panels offer much higher manufacturing yields than their larger counterparts. LCD panels are created in large batches, with many displays occupying a single sheet of glass. Think of it like CPU fabrication, but on two-meter glass substrates. Larger panels mean fewer screens can be squeezed out of a single substrate. Entire panels must be scrapped if defects exist, even if they only cover a relatively small area, making defects costlier with larger displays. With smaller screens, manufacturers can squeeze more panels onto a single sheet of glass, reducing the amount of waste due to localized defects.

Beyond yields, there is also the matter of capacity. If manufacturers are able to saturate their production lines with smaller displays that offer good yields and consistently sell for a tidy sum, there is little incentive to risk the time and materials on larger panels that may be less profitable. Some vendors have dabbled in high-PPI desktop displays; over a decade ago, IBM pimped a 22.2" 3840x2400 IPS panels to the medical imaging community. That's a niche market where exorbitant prices are common, though.

Tackling the manufacturing issues involved in creating large, high-density panels is only half the battle. Software compatibility is another hurdle that must be overcome. As much as I want to live the illustrious life of an Apple hater, I feel like the Mac maker has approached the high-resolution conundrum the right way with its Retina displays. By starting with a usable base resolution and increasing the number of pixels by a factor of four in the same area, software can use simple scaling to take advantage of the extra pixels without making all the icons and menus microscopic.

By contrast, the high-density display on Sony's Z-series ultraportable runs into issues. Even with an impressively dense 1920x1080 pixels under its 13" belt, the screen isn't conducive to the same seamless upscaling of fonts and icons as the iPhone or iPad. To accomplish that feat, the base resolution would have to be set at a paltry 960x540 to offer the ideal factor-of-four upscaling to 1080p.

Just the other day, Cyril reported on Windows 8's upcoming scaling features for high-density displays. This scaling is designed to allow 10.1" and 11.6" tablets with 1920x1080 resolutions to display fonts and GUI elements smoothly and macroscopically. The end results remain to be seen, but I would really prefer to see PC manufacturers set their sights on 4X scaling rather than cutting corners with odd upscaling ratios.

When might we reasonably expect high-PPI goodness to permeate laptops and desktop monitors? Sooner rather than later, I hope. Higher-resolution screens have started seeping into premium ultraportables, and Apple is expected to incorporate Retina panels in its next line of MacBook laptops. Stand-alone monitors will probably take longer to catch up, which is a shame considering how many of our readers are pining for higher pixel densities on their desktops.

The success of the fledgling quad-HD (4K) video format will be another crucial factor in the adoption rate of high-resolution displays. The native resolution of 3840x2160 fits the factor-of-four criteria perfectly and provides a new, exciting canvas for video artists to paint on. As a matter of fact, YouTube already hosts a small collection of 4K videos for your bandwidth-crushing pleasure.

What if you don't really care about 4K video just yet? What if sharper text doesn't get your motor running? What else could a dramatic increase in pixel density do for the PC? Make games look better, of course. Adding pixels allows for more detail, and making pixels smaller reduces the need for antialiasing algorithms that can slow down rendering—although, on the flip side, your graphics card will have more pixels to render. With more pixels comes more computing responsibility.

Well, I'm landing now. Time to wrap this up. While my jet-lagged ranting probably won't get super-duper-dense LCDs into our notebooks and desktops any faster, perhaps we can still make a difference. Gentlemen, gather your picket signs and MRE pouches! At the very least, we can raise awareness about the obscene, Volkswagen-sized pixels commonly found on consumer notebooks. Occupy Best Buy! Who's with me? *crickets*

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