Super AMOLED Plus vs. Retina vs. Super LCD vs. Nova screens: What's the difference?

(Editors' note: This is a primer for people who are unfamiliar with screen technology. If you're already well-versed, you might be more interested in my colleague Eric Franklin's screen tests, like this one between the iPhone 4, Morotola Droid X, HTC Incredible, and the Samsung Epic 4G.)

I don't know anyone who doesn't want their smartphone screen crystal clear, with saturated colors leaping off the display. But unless you're a screen tech buff, it isn't always easy knowing the difference between premium screens with fancy names like LCD Plus, Super AMOLED Plus, and Retina Display--and how they really affect the viewing experience.

We editors often describe awesome screens as "brilliant," "eye-popping," "rich," "smooth," and "gorgeous." Meanwhile, screen techies (and sometimes marketers) use terms like "color gamut," "NTSC," "filter matrix," "sub-pixels," and "luminance."

I'm no display technologist, but like many of you, I wanted to know what makes one screen "better" than another, and by which measure. So I dug around online, spoke at length with a couple of display experts, and tracked down answers from Samsung, HTC, LG, and Apple (which wasn't very helpful.)

It turns out that what makes a screen shine is a complicated, and often proprietary, blend of resolution, brightness, and color reproduction, with some other angles thrown in. To make it easier to follow, and to keep from sounding like a text book, I'll use a handful of flagship phones as examples of what makes your killer screen so lethal to the run-of-the-mill displays.

What's in a name?

Apple, LG, Samsung, and Sony own the names for their screens and the technology that goes into them. It gets a bit confusing because proprietary names often mirror general terms. The "AMOLED" In Samsung's Super AMOLED Plus screen stands for "active-matrix organic light-emitting diode," but some of that is there for emphasis. Most of today's OLED screens already employ "active matrix," a common way of dealing with pixels on a liquid crystal display. The same goes for Super LCD, a brand name for Sony's specific makeup of a liquid crystal display. Then there are screen names that seem purposely vague. Apple's Retina display evokes human vision without revealing the technology behind it, and LG's Nova screen simply states that it's new.

iPhone 4: Resolution

Part of what makes the Apple iPhone 4 so "magical," at least to CEO Steve Jobs, is its high pixel density. Once you reach a certain number of pixels per inch (ppi), Apple says, the human eye can no longer detect the difference between them, which makes the image look perfectly smooth. If you believe Apple, the 326 pixels per inch (ppi) of its Retina display is pretty close to the magic number. Indeed, it looks nice and sharp.

To achieve this, the iPhone 4 features a 960x640-pixel resolution on a 3.5-inch screen. The Retina display's resolution is still the one to beat, but screen size is also key. For instance, the forthcoming Motorola Droid Bionic will feature a quarter-HD (qHD) 960x540-pixel resolution on a 4.3-inch screen. Although the Bionic's resolution approaches that of the iPhone 4, its (fewer) pixels will spread out on a notably larger screen, making the overall density smaller. There are other factors in addition to resolution and density that contribute to a sharp viewing experience, but the main point is that your eye will notice too few pixels on a too-large screen. For reference, DisplayMate.com includes pixel density as one factor in a detailed comparison chart.

LG Optimus Black: Brightness

LG boasts that the Nova screen on its forthcoming LG Optimus Black smartphone has 700 nits. If this conjures images of sticky lice eggs, think again. "Nits" in this case refers to a unit of light measurement, also known as candelas (cd/m2). 700 nits is indeed very high, I'm told. For the sake of comparison, the iPhone 4 screen has approximately 500 candelas at maximum brightness.

Why does brightness matter? Simply because the higher the nits, the better you'll be able to view the screen in direct sunlight, and the brighter it'll look indoors. Keep in mind, however, that the number of nits printed on a spec sheet could represent a lab ideal. Your eyes may see fewer than the promised 700 nits in real life once the glass screen is installed, and you obviously lose brightness once you dim the screen to reduce power consumption.

Samsung Super AMOLED Plus: Colors

I personally enjoy looking at the bright, colorful Samsung Galaxy S II and Samsung Droid Charge's Super AMOLED Plus screens. Even compared with the good-quality Super AMOLED screen, the colors in icons, apps, photos, and videos appear richer and more saturated on the Plus. Edges are finer, and text is sharper and easier to read.

What accounts for the improvement between the Super AMOLED and Super AMOLED Plus displays is a subunit known as a subpixel. Sub-what? Like human cells, a pixel is made of composite parts. In screen technology, it's broken into red, green, and blue subpixels, which help control the colors you see on the screen. The Super AMOLED Plus screens have 1,152,000 subpixels, a 50 percent increase over the 768,000 subpixels in the Super AMOLED display.

To make matters more confusing, competing companies arrange subpixels in various formations to tease out different results. Take the Motorola Atrix 4G, for instance. Although it has a qHD 960x540-pixel resolution, it also has two rather than three subpixels per pixel. According to Display Mate president Raymond Soneira, that makes images appear less sharp than they could (the Atrix certainly isn't the only phone to use this particular pixel arrangement.) This highlights a trade-off between the sharpness produced by the number of subpixels and how effectively they transmit colors in their various arrangements. That leaves room for debate amongst the pixel pundits as to which arrangement is best, but most smartphone owners will notice only gradations of sharpness and brilliance.

Eye-pleasing extras

There's much more, too, that goes into a killer screen. The contrast ratio accounts for bright whites and inky blacks. The extremes are hard to achieve, but the closer a screen can get to the absolute digital white and black, the better.

Then there's the color gamut, which helps frame how well the colors on the screen compare to what the human eye perceives in real life (DisplayMate has a great explanatory chart here.) This is especially evident in smartphone photography and video playback, although there's more going on with camera software than just the screen's ability to reproduce hues.

Viewing angle is another element that's associated with different screen brands. It denotes how far you can be from the center of the screen to still see the image. At 180 degrees, the Samsung Super AMOLED Plus has the widest reported viewing angle of the four screen types we looked at, closely followed by the Nova at 170 and the Super LCD at 160 degrees. Apple wouldn't share the measured viewing angle of the Retina display. What we do know is that Apple uses a certain high-quality LCD material called IPS (in-plane switching,) which would put its viewing angle in the same ballpark as rivals.

Finally, there's the software factor. As good as the screen technology is, the device still needs a great graphics processor (GPU) for quickly rendering images, especially for fast-moving videos and games. The better the GPU does that, the better everything can look on the screen.

Tying it all together: Quality matters

The screen isn't the sole reason to buy a phone, but since it's the part you look at most, it could tip the scale between two otherwise equal handsets. An excellent viewing experience can also make a phone seem more premium. Apple's Retina display reigns supreme in terms of pixel density and resolution, but as far as I'm concerned Samsung's Super AMOLED Plus screen rivals and arguably bests it in terms of reproducing color and sharpness on a larger display. SuperLCD screens are still quality, but the technology seems to trail behind the Retina display and the new Super AMOLED Plus.

While we took a brief look at LG Mobile Display's Nova screen at CES, CNET's crew hasn't been able to do any real comparison testing. You can bet that CNET's Eric Franklin will conduct a thorough smartphone screen Battle Royale (here and here) when we get all screens side by side in our office.

The good news is that screen quality is getting sharper and brighter all the time. There's no shortage of excellent premium phones out there, but for my money today, the Super AMOLED Plus screens on the Samsung Droid Charge and (unlocked) Samsung Galaxy S II offer the best viewing experience and some of the top smartphone experiences overall, with the also-excellent iPhone 4 right in the mix.