Experts weigh in on iPhone 4 display quality

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It’s not every week that Apple ignites a controversy. Okay, maybe that’s not true, but it’s not every week that Apple ignites a controversy that pits physicists, astronomers and neuroscientists against one another. But that’s what happened with the introduction of the iPhone 4 and its high-resolution Retina display.

During his keynote at this year’s Worldwide Developers Conference, Jobs tried to explain just how impressive the resolution of the iPhone 4’s new 326-pixels-per-inch Retina display really is:

It turns out that there’s a magic number right around 300 pixels per inch, that—when you hold something around 10 or 12 inches away from your eyes—is the limit of the human retina to differentiate the pixels. And so they’re so close together when you get at this 300 pixels per inch threshold, that all of a sudden things start to look like continuous curves… Text looks like you’ve seen it in a fine, printed book. [It’s] unlike anything you’ve ever seen on an electronic display before. At 326 pixels per inch, we are comfortably over that [300 pixel] limit.”

After the event, our live coverage team of Jason Snell and Dan Moren got to look at the real, live device. They wrote:

We couldn’t pick out any pixels on the iPhone 4’s text; as Apple claims, this screen really makes text look like something you’d find in a book or a magazine, with none of the artifacts that we’ve come to expect from a LCD display… Photos and videos are absolutely spectacular on the iPhone 4. It really is like looking at a self-illuminated photographic print, not a computer image.

Macworld Senior Contributor and Daring Fireball pundit John Gruber also got to meet the iPhone 4 in person. He wrote: “The resolution of the ‘retina display’ is as impressive as Apple boasts. Text renders like high quality print.”

So is seeing believing? This is where it gets sticky. Wired’s Brian X. Chen, who was also present at the Apple event and saw the device for himself afterward, wrote a piece with the surprisingly definitive headline, “iPhone 4’s ‘Retina’ Display Claims are False Marketing.” The story’s lead sentence: “The iPhone 4’s screen may be the best mobile display yet, but its resolution does not exceed the human retina, as Steve Jobs claims.”

Wired’s confident claims that Steve Jobs was fibbing were apparently the result of a single source: a physicist named Raymond Soneira, the president of DisplayMate Technologies. According to Chen, Soneira has studied displays for 20 years. Soneira told Chen: “[The iPhone 4’s screen] is reasonably close to being a perfect display, but Steve pushed it a little too far.”

Soneira objected to Jobs using pixels as a measurement of eye resolution in the first place, because eyes use something called angular resolution, while a flat display uses linear resolution. After working the numbers, Soneira concluded that a genuine “retina display” would need 477 pixels per inch to look perfect from a foot away.

Piling on was PCWorld, which ran its own interview with Soneira. He told them that unless you held the iPhone 4 at least 18 inches away, it couldn’t achieve retina quality. He added further that the iPhone “actually needs a resolution significantly higher than the retina in order to deliver an image that appears perfect to the retina.”

But just as the Internet makes it possible for news organizations to call corporate CEOs liars based on the opinion of a single physicist, it also makes it possible for other experts in the field of optics to come out of the woodwork to question the statements of a single physicist.

First up was Phil Plait, author of the popular Bad Astronomy blog and a scientist who knows a thing or two about optics and resolution based on the work he did calibrating a camera on the Hubble Space Telescope. Plait deconstructed Soneira’s entire argument and explained just what people mean when they’re talking about resolution.

In the end, Plait’s verdict was that while Soneira is correct that a person with perfect vision would be able to detect pixels on the iPhone 4’s display held 12 inches from their eyes, a person with average eyesight (20/20, let’s say) would not be able to detect those pixels. Plait concluded that both Jobs and Soneira spoke accurately, and suggested that Wired is the party at real fault for blowing the story out of proportion and writing a misleading headline. “Jobs wasn’t falsely advertising the iPhone’s capabilities at all,” Plait concluded.

Filing a separate dissent was William H.A. Beaudot, a Montreal-based vision scientist and founder of KyberVision, who spoke with fellow Canadian Jim Dalrymple of The Loop.

“In my opinion, Apple’s claim is not just marketing; it is actually quite accurate based on a 20/20 visual acuity,” Beaudot told The Loop. Like Plait, Beaudot points out that the minimum distance between two points that a 20/20 eye can resolve is one arc minute, or one-sixtieth of a degree.

Nobody likes to be criticized on the Internet. So Soneira, the original scientist who criticized Jobs’s claims for Wired and PCWorld, e-mailed a follow-up comment to PCWorld:

“There have been some comments that my analysis is for perfect vision. Jobs’ statement is for the *retina* not the *eye* with a poor lens. If you allow poor vision to enter into the specs then any display becomes a retina display…. Allowing puffery and exaggerations in the sales and marketing starts a snowballing effect that eventually leads to the 1000% rampant spec abuse that I document for many other displays.”

Leaving aside whether “1000% rampant spec abuse” is a viable statistic (implying, as it does, that more specs than actually exist could be deemed abusive), it appears that Soneira’s retort doesn’t acknowledge Beaudot’s counterargument that the iPhone 4’s display actually does satisfy retina-quality requirements for folks with 20/20 vision.

So where does that leave us? Well, if you’ve read this far your eyes are probably a little tired. But in the end, it seems like science has spoken. Are Apple’s iPhone 4 display claims “False Marketing,” as Wired claimed? It seems like they aren’t for the vast majority of users, though the most eagle-eyed types may still be able to detect the pixels.

Even Soneira, who admirably attacks bogus display marketing wherever he finds it, admits that the Retina display is an impressive achievement: “It’s a great display,” he told PCWorld. “Most likely the best mobile display in production (and I can’t wait to test it).”

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