ABCs of smartphone screens: 1080p and more (Smartphones Unlocked)

We have plenty of names to describe the viewing quality on your smartphone screen, but few of them actually make sense. Here's what matters, and why.

Nokia Lumia 1020
The Nokia Lumia 1020 features PureMotion HD+ technology, a ClearBlack display, and supersensitive screen. Beg pardon? Sarah Tew/CNET

The smartphone industry tosses around a whole bucket of names and numbers to describe the viewing experience on your smartphone screen: ClearBlack, 1080p, Retina, AMOLED, supersensitive. And the list goes on.

Some designations are marketing monikers cooked up to give one company an edge; others are more scientific. That isn't to say that flashy names like Apple's Retina Display are worthless and empty. Sometimes the trademarked name masks a unique process too technical to quickly explain.

To make things simpler, here are some common terms you might see attached to smartphone screens, and some factors that actually go into making your screen a standout, like the physical screen materials, LCD versus OLED, brightness, color accuracy, and pixel resolution. Got all that? Good. Now let's dive in.

Common smartphone screens
The terms often used to describe smartphone screens aren't always so clear.

The anatomy of a smartphone screen
Before we dive in, it's helpful to understand the layout of a smartphone screen. The oversimplified version is that displays are composed of several layers of material, starting backing material and including a lighting element (like the backlight for LCD screens), which is then topped with a TFT (thin-film transistor) layer, which uses voltage-sipping transistors to keep the display's pixels shining until you refresh or change the image.

There's also the touch-sensitive panel; various films and filters that might reduce glare, for instance; and the cover glass, which is often bonded to the touch layer. Gorilla Glass is one designer brand of cover glass.

AMOLED screen technology
An AMOLED display comes together. Wikipedia.org

LCD versus OLED
There are warring schools of thought between the two types of display technologies: LCDs (which act as valves to allow varying amounts of the backlight through to the viewer) or AMOLED/OLEDs (a different approach that uses "active-matrix organic light-emitting diodes" to directly emit light).

There are complex ins and outs, but in a nutshell, you can think about LCDs and OLEDs as follows:

LCD screens start with an always-on backlight; this technology requires light to create black, white, and colors. High-end LCDs produce the most accurate colors, though their manufacturers sometimes intentionally calibrate LCDs to produce weaker red, blue, and purple shades in order to reduce the device's power consumption.

LCDs generally age slower, with their brightness and color balance holding up fairly well over thousands of hours of use.

OLED, on the other hand, doesn't require any light to produce black, only white and colors. Therefore, it's considered battery-saving (since it requires no energy to create black) and can produce inky blacks. OLEDs are often considered brighter as well, creating punchy hues. As a side effect, OLED screens tend to oversaturate the color green.

OLEDs also age more rapidly than LCDs, according to experts, which means that the red and blue colors deteriorate faster than green, which can further throw the color balance out of whack.

OLEDs can also be expensive to make, and in the past, limited production has caused some manufacturers, like HTC, to switch from AMOLED to LCD screens.

Samsung's Galaxy S4 uses an OLED screen; the HTC One rocks LCD. Sarah Tew/CNET

What is IPS?
What makes the two differing technologies more confusing is that there are multiple versions of each. For instance, IPS (in-plane switching) is a type of premium LCD technology that's touted for its wide viewing angle and clearer picture. The iPhone 5 is a prime example of a phone using IPS panels.

So what about Super AMOLED?
Samsung makes most of the OLED smartphone screens, naming its line Super AMOLED.

These days we see mainly HD Super AMOLED phones with high-pixel resolutions, but Samsung has also made Super AMOLED and Super AMOLED Plus screens; the shift from Plus to HD Super AMOLED is a controversial one among pixel buffs, and one that quickly becomes technical.

RGBG PenTile matrix
PenTile matrix, RGBG Wikipedia.org

Each screen pixel is actually composed of red, green, and blue subpixels that can turn on and off in combination to create any supported color combination (turn them all on at full blast to shine white).

There are numerous ways to pattern the subpixels. Super AMOLED (and HD Super AMOLED) uses Samsung's PenTile layout and its pattern of red, green, blue, green (RG-BG) subpixels.

PenTile, in fact, uses fewer red and blue subpixels than it does green. As such, PenTile also has fewer subpixels than the typical RGB layout found in LCDs and in AMOLED screens used by other companies. Examine a PenTile screen closely and you might be able to detect a little more image granularity when you're looking at fine details and text. For the most part, though, your eyes fill in the blanks.

Some people preferred Samsung's Super AMOLED Plus pixel arrangement for creating a technically sharper image with three subpixels per pixel, rather than the two subpixels in the non-Plus version that Samsung's flagship phones like the Samsung Galaxy S4 have today.

AMOLED versus Super AMOLED Plus
Samsung

Although Samsung didn't comment for this piece, an employee of Samsung America (but not Samsung Display) has said elsewhere that PenTile is more durable. It's also cheaper to make than Super AMOLED Plus, and it has some battery-saving efficiencies, since there are fewer subpixels that the battery has to power.

Pixel density
Generally speaking, though, the more pixels you have per inch (ppi), the better your picture. So smaller screens should look crisper than larger screens when both have the same pixel density.

That said, Apple claims that the human eye can't really distinguish more than 326 pixels per inch. Screens with 1080p HD resolutions typically hover in the 5-inch range, delivering pixel densities in the high 300s to 400s.

 
HTC One

Samsung Galaxy S4

iPhone 5

Screen size
4.7 in.
5 in.
4 in.
Resolution
1,920x1,080
1,920x1,080
1,136 x 640
Pixel density
468ppi
441ppi
326ppi

While pixel density is an important factor in the smoothness of the overall picture, it's just one facet of many. And when it comes to comparing smartphone pixel density with that of a tablet, you don't necessarily need the same high density. DisplayMate's Soneira explains here how fewer pixels can satisfy your eye when reading from a tablet you hold farther from your face than you would want from a smartphone, which has a smaller form factor and is often held closer.

Brightness and color
It's as true with smartphones as it is with HDTVs: people's eyes are often drawn to the brightest and punchiest of the pack, blue blues and green greens that are rich and saturated, but just not true to life.

Oversaturated color gets tiring, and just looks cheap or fake when you're viewing something so familiar that your eye knows it's being fooled -- a video or photo of something you just know isn't that candied.

Some OLED devices do contain settings to dial down the juice, but you'll have to go hunting in the sub-menus to find more realistic tones.

Reflection, the secret enemy
Ever take your phone outside and squint to read the screen? Phones with high reflectance can be a real setback, but some manufacturers are good at getting on top of it. Nokia applies its ClearBlack filter above the touch layer (but below the glass) on its high-end phones. It works on both AMOLED and LCD screens.

Huge yellow fireball at sunset
iStockphoto

The ClearBlack filter uses "circular polarization," which forces light to travel in a clockwise direction, then blocks off all the light that bounces back to the screen in a counterclockwise direction. The end result is reduced reflectance overall, and improved legibility both indoors and outdoors.

Who's doing it best?
Nokia, Apple, Samsung, and HTC all produce high-end phones teeming with pixels, and the LCD versus OLED color reproduction question often comes down to a matter of personal preference.

When it comes to technical proficiency, which you can measure in a lab using calibrated instruments, CNET's lab test found that the Galaxy S4 screen edges the HTC One overall, but not in every category.

While all smartphones are harder to read in direct sunlight, I give Nokia a lot of credit for working on outdoor legibility. Of these four top phone-makers, I've personally had the most problems with Samsung's screens fighting the sun's rays.

Still, my ultimate buying advice is this: stare at the screen long and hard on automatic mode (the one you'll use most to save battery), and hold it up next to other rival devices in the store. If you can live with it, if you never notice overly dull or artificial colors, or a distracting reflection, and if you feel you can read small text without blurriness or eye strain, then there's no reason to let the specs determine your purchasing path.

Smartphones Unlocked promo image
CNET





Smartphones Unlocked is a monthly column that dives deep into the inner workings of your trusty smartphone.

 

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