Does the iPhone 4 Really Have a "Retina Display"? (Updated)

[Updated 06/11/10, see below]

Dr. Raymond Soneira runs DisplayMate Technologies, which makes software to test display quality. He has a PhD in Theoretical Physics from Princeton University, and was a Long-Term Member of the Einstein Institute for Advanced Study in Princeton. (Read Dr. Soneira's Bio.) He also knows more about digital displays than just about anyone I know - and I know some pretty tech-savvy folks. This morning, Dr. Soneira shot me an interesting email regarding the so-called "Retina Display" of the iPhone 4. To clarify: a retina display is one whose resolution meets or exceeds the maximum resolution the human retina is capable of resolving, assuming perfect vision.

This is a bit tricky, since the eye doesn't have "pixels" and the resolution required to match the human eye's capability depends on the distance from your eye to the display. If you sit four feet away from a 50" 1080p television, you'll see pixels. If you sit 100 feet away, you won't. The distance between any two visual elements is a matter of how many pixels per "arc degree" of vision it covers. Dr. Soniera's email, in full and unedited, is as follows.

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The iPhone 4 has an outstanding display... and I'm glad that Apple resisted the emotional rush to OLEDs because they still need lots of improvement before they will be ready to compete with the highly refined IPS LCDs. The iPhone 4 display should be comparable to the outstanding IPS LCD in the Motorola Droid, which I tested and compared to the Nexus One OLED, which was trounced by the Droid.

Steve Jobs claimed that the iPhone 4 has a resolution higher than the retina - that's not right:

1. The resolution of the retina is in angular measure - it's 50 Cycles Per Degree. A cycle is a line pair, which is two pixels, so the angular resolution of the eye is 0.6 arc minutes per pixel.

2. So if you hold an iPhone at the typical 12 inches from your eyes, that works out to 477 pixels per inch. At 8 inches it's 716 ppi. You have to hold it out 18 inches before it falls to 318 ppi.

So the iPhone has significantly lower resolution than the retina. It actually needs a resolution significantly higher than the retina in order to deliver an image that appears perfect to the retina.

It's a great display, most likely the best mobile display in production (and I can't wait to test it) but this is another example of spec exaggeration.

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So there you have it - some math from a display expert showing that, while the iPhone 4's display is certainly exciting and probably represents a step forward for smartphones, it may fall short of Apple's claims of meeting or exceeding the resolution of the human retina.

Update 06/11/10: Dr. Soneira sent us some additional information, clarifying some of the misconceptions flowing around in comments and on other sites. He wishes to stress that his comments do not mean that he thinks the iPhone 4 display (or the phone itself) is bad. On the contrary, he thinks the display seems like a significant step forward. Dr. Soneira's comments are only regarding the claim Steve Jobs made of 300 pixels per inch being all that the retina can distinguish at a distance of "10 to 12 inches." Dr. Soneira's update is as follows

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The iPhone 4 is actually very far from a retina display. It's a substantial discrepancy and not even close: At 12 inches the 1 dimensional linear difference is 326/477 = 68 percent. But the pixel (area) density for two dimensions, which is the actual relevant observable, is that value squared = 0.47, so the iPhone 4 is more than a factor of two from being a retina display at the typical 12 inch viewing distance. Stated another way: The iPhone display would need to have 1.3 megapixels instead of 0.6 megapixels to be a retina display.

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. That turns it into a meaningless concept that will be exploited by everyone. The iPhone 3GS is a retina display too for good percentage of the population.

Specs need to be objective, precise and accurate. 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.

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Another Apple iPhone 4 Flaw: A Glitchy Proximity Sensor

It happened to me on my first phone call with the new Apple iPhone 4: The display screen flashed on during the call, and I managed to inadvertently put the call onto speaker. Twice.

Now, I could crack a joke about having a talented cheek, but this isn't a joking matter: I never had these problems with my iPhone 3G or iPhone 3GS. I didn't feel as if I was holding the phone any differently; I even paid close attention over the course of subsequent e-mails, and confirmed I wasn't doing anything different.

What I did notice as the weekend wore on, however, was this was not a one-off occurrence. I regularly activated the touchscreen during a call. Typically, I managed to activate the keypad (and subsequently dialed numbers), mute button, or speaker; sometimes I ended up going into the contacts screen, or activating FaceTime (which in turn gave me an error message, given that I wasn't on Wi-Fi).

The clear suspect in this bizarre behavior appears to be the iPhone 4's proximity sensor, mouthful of a term that describes the sensor that detects your face's location relative to the screen, and enables or disables the display accordingly. On the iPhone 3GS, the proximity sensor was located to the left of the earpiece speaker. But that space on iPhone 4 is now occupied by the front-facing camera, and the proximity sensor is above the earpiece.

What's not clear is whether the iPhone 4 screen's misbehavior is due to the new location of the sensor, or it's because Apple tweaked the sensor's responses in any way. It could even be a combination of both.

In use, I observed out of the corner of my eye that the screen would blink on and off intermittently, depending upon how I held the phone. It was almost an assumption that I'd see this behavior if the phone slipped just slightly away from or up from my face. And it happened consistently whenever I rested the phone between my head and my shoulder-a common position, albeit one my neck never particularly appreciates.

(Separately, the new proximity sensor location is a major reason why you shouldn't attempt to use an iPhone 3GS case while waiting for an iPhone 4 case, even though the latest-gen cases are almost as hard to find right now as an actual device. It's also one of the reasons why many case designs remain in development and are not yet available, according to Ramsey Oten, CEO and case designer for Sena Cases. Notice that the earliest designs are either pouches, or form-hugging designs like Apple's own bumper, and similar designs from Sena and Incipio.)

While little official is known about this issue yet, I found it incredibly annoying to have my calls routinely interrupted. I asked around and found my colleague, Ginny Mies, had similar experiences. And some digging online shows Apple has an open discussion thread running 19 pages long, and counting. There, a user reports that an Apple Store Genius tech said it was "probably a software issue" but still put that user in line to swap out the phone when they get more in.

Sadly, I wouldn't get your hopes up on a swap helping matters. I'm already on my second handset, and have experienced the proximity sensor problem with both. Each was a "clean" install, meaning I didn't restore from a backup or anything else that might have impacted iOS 4's settings. To be fair, that first handset had other issues, too--the phone app froze up twice, each time requiring a reboot, and multiple times, the touchscreen didn't respond, period (among other things). But shortly into my second call with the second handset, the proximity sensor problem kicked in again, and I activated the keypad. In my experience, I'd say it's not an isolated hardware issue.

In these early days, it's not clear if every handset is affected--heck, many users have gone straight to using a Bluetooth headset or haven't really used the phone for conversation. Nonetheless, it is clear that this is yet another iPhone 4 launch problem Apple needs to address. Soon.

In fact, I'd put this call interruptus problem right up there with the reception issues. Yes, like so many others, I can hold the iPhone 4 in the so-called death grip and watch its signal strength deteriorate bar-by-bar, but I have not dropped calls because of this problem; I just drop calls in the same locations where my iPhone 3GS always dropped calls. At least the reception issue can be solved by using a case, something most of us will do, anyway, once cases become widely available. But short of using a headset--which no phone should require--the continuous and awkward call interruptions appear unavoidable until a fix comes along.

Have you experienced wonky behavior from your iPhone 4's touchscreen and proximity sensor? Tell us in the comments.

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HP Envy 14 Now Available for Order

Back in early May, we wrote about the slew of new notebooks announced by HP. Some lines received bigger updates than others, but one of my favorites of the bunch was the Envy 14. Set to replace the end-of-life Envy 13, the new Envy notebooks clearly take their visual cues from Apple's MacBook Pro line. The new Envys are not only slick and pretty, but sport some pretty great hardware. Though the entry price of $1,099 for the 14-inch model is a little hard to swallow in a market where everyone wants a $599 notebook that does everything, it's worth noting that you get a lot more bang for the buck,hardware-wise, than a comparable MacBook Pro.

Consider that the 13" MacBook Pro starts at $1,199. For that extra $100, you get a similar CPU (2.4 GHz Core 2 Duo compared to the 2.4 GHz Core i3-370M in the Envy 14), equal RAM (4GB), a smaller hard drive (250GB vs. 320GB), and quite inferior graphics (GeForce 320M with 256MB of shared memory vs. Mobility Radeon 5650 with 1GB dedicated graphics memory). Oh, and the Envy has a higher-res screen as well (1600x900 vs. 1280x800), but then again, it's a little bit bigger. Choose enough upgrades to boost the price to the next-best MacBook Pro (the $1,499 13-inch model) and the difference in specs tilts even more heavily in the Envy 14's favor.

Of course, a good laptop is more than the sum of its hardware specs, and we haven't had a chance to review the Envy 14 just yet. We're anxious to put it through its paces and you'll see a review here as soon as we can. If you want to jump in before our review, you can order an Envy 14 from the HP store.

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Samsung N230 Netbook Promises 13.5 Hours of Battery Life

Samsung announced a new netbook model today in the N230. At first blush, it doesn't seem like anything particularly special: a 10.1-inch screen with a resolution of 1024 by 600, Intel Atom N450 or N470 CPU, 802.11b/g/n Wi-Fi, and a weight of around 2.2 pounds. The eye-catching part is the company's claim that this netbook will last for 13.5 hours on a single charge. How is it achieving such astounding battery life from a regular Windows-running netbook? Samsung talks about their efficient LED display and "proprietary Enhanced Battery Life (EBL) solutions" in its press release, but upon closer examination we can see what's really going on...

The N230 netbook has a high, but not especially amazing, battery life of 7 hours with the standard battery. The 13.5 hour claim comes when you use the optional 65 watt-hour long-life battery. Samsung doesn't say exactly what this battery will do to the netbook's bulk or weight. Still, this is an impressive feat, if the real battery life is anywhere close to Samsung's claims. We have tested netbooks with extended batteries before, and none have quite come close to that sort of runtime. Then again, we often find the battery life claims of manufacturers to be a bit...optimistic...compared to our lab tests.

Samsung says the N230 is available now and should cost around $400, but we haven't seen it pop up on our favorite shopping sites just yet.

Check out our Top Netbooks Chart .

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