Behind the specs of Apple's Retina display

Apple's new iPhone 4 has an all-new display the company is calling Retina. How is it better?

"So that is the Retina Display. Awesome text, awesome images, and awesome video." -- Apple CEO Steve Jobs on the iPhone 4's new screen, Apple Worldwide Developers Conference, June 7 2010 James Martin/CNET

One of the most hyped features of the new iPhone, known as iPhone 4, is the new screen. Apple bombastically calls it the Retina display, citing a host of improvements over the current screen, which has gone three years without a major update. But what does it all mean?

Judging from the specs alone, the new screen will look better than before. That's a good thing by objective standards, and we'll get into the improvements below, but first a word of caution about relying on published specs when it comes to screens in general.

Improvements, especially resolution, tend to have diminishing returns--it's really tough to see the difference between same-sized 1080p and 720p TVs with moving video, for example. The way a manufacturer implements the technology, for aspects like color reproduction, reflectivity, and gamma, can have a larger impact on image quality than any published specs. Finally, the content, the viewing environment, and even your own visual acuity all affect how an image will look to you on the new iPhone 4's screen.

960x640 resolution: This is the native resolution of the Retina display, which crams 614,400 pixels onto a 3.5-inch diagonal screen (326 pixels per inch). That's four times as many pixels as the current iPhone, which has a 320x480 native resolution on the same-sized screen (163 PPI), and significantly more than newer competitors like the Motorola Droid (854x480, 265 PPI) and the Nexus One (800x480, 252 PPI), for example. As Jobs pointed out, 300 PPI is typically regarded as the limit of useful pixel density, and the iPhone 4's mark of 326 is among the best available on any display.

Text, especially smaller fonts, should appear sharper and less pixelated when you look closely in a side-by-side comparison between the old and new iPhones. The difference with photos will be a lot more subtle, on the other hand, while the difference with moving video might not be visible at all. It's simply easier to see differences in resolution with black-and-white, line-based material, especially when it's not moving. In any case, you'll have to look closely to see them. Compared with other screens with higher pixel densities than the current iPhone, the differences in detail will be even smaller.

We say "should" because material that's not designed for the higher resolution--Jobs said the new iPhone iOS 4 would be, and encouraged App designers to update to higher rez--has to be scaled to fit the pixels. It's the same as watching a DVD (720x480) on a typical high-definition TV (1920x1080); it will look good, but since it's not a high-resolution source to begin with, the extra pixels are basically wasted. A typical YouTube video on the new iPhone 4, for example, won't benefit from the extra pixels. Icons and photos in the browser, on the other hand, might indeed look slightly better if Apple does the scaling correctly.

The analogy between an HDTV and an iPhone 4 can be misleading, however, because the distance between your eyes and the screen is so different. Holding the iPhone six inches from your face, you'll be able to appreciate differences that simply aren't visible on a screen 10 feet away. The closer you hold the screen, the more apparent the improved pixel density will be. And larger images--like, say, the massive iPhone 4 projections Jobs used to illustrate the Retinal display during his speech--show off the differences better as well.

The difference between the old and new iPhones' resolutions should be apparent in material designed for the new display, like iOS 4. James Martin/CNET

800:1 contrast ratio: This describes the ratio of the darkest black to the brightest white a display can produce. Contrast ratio specs are easy to inflate depending on how you measure them, and usually measured in low ambient light situations that are uncommon to experience in real life with a phone. More important are the reflectance properties of the screen (how it handles ambient light), an issue that was not addressed in Jobs' speech.

I couldn't find Apple's official contrast ratio spec for the current iPhone screen, although Apple says the new one is four times better. According to a comprehensive DisplayMate test, current iPhone contrast is extremely low and "washed out." We're pretty confident the new screen will be an improvement, although we doubt it will match the depth of black seen on OLED screens.

IPS technology: Speaking of OLED, Jobs called the IPS-based (in-plane switching) LCD screen used by Apple "quite a bit better than OLED." That remains to be seen, but in general, OLED will produce higher contrast, by virtue of its ability to display a darker black, stay truer from off-angle, and draw less power with the screen turned down. Conversely, LCD (and IPS) will be more efficient at high brightness and not wash out as much in high-ambient-light situations. Both technologies, when implemented well, can look great on phones, but in our view IPS is certainly not better by default than OLED or AMOLED. The same goes for the LED backlight and ambient light sensor Apple uses--their main benefits are realized in increased efficiency.

In conclusion, we suspect the iPhone 4's screen will bring a visible improvement over the current, outdated iteration, and rival the best phone screens currently available. But it probably doesn't deserve to be named after an eye part. On that note we're looking forward to the company's introduction of the Phalanx keyboard.

 

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