Apple's iPhone 4: Thoroughly Reviewed
by Brian Klug & Anand Lal Shimpi on June 30, 2010 4:06 AM EST- Posted in
- Smartphones
- Apple
- iPhone 4
- Gadgets
- Mobile
Screen - Retina Display
Right out of the box, the iPhone 4's new 326 PPI, 960x640, 3.5" display is arguably the single most striking change the new iPhone brings. In a word, it's dazzling. Text and high res images look amazingly sharp on the iPhone 4’s retina display. It’s an improvement over the 800 x 480 AMOLED screens that have been shipping on most Android phones. But if you’re comparing it to an iPhone 3GS the difference is huge.
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iPhone 3GS
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iPhone 4
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Text on the Google Nexus One
Text on the iPhone 4
The dot pitch is truly remarkable, so much so that Apple makes the claim that their display outresolves the human eye; its advertised ability to do so has earned it a new Apple tradename, "retina display."
Text on the HTC EVO 4
Text on the iPhone 4
AnandTech Logo on the EVO 4G
AnandTech Logo on the iPhone 4
Immediately after hearing Apple's claim that the Retina Display outresolves the human eye, I snapped into optics mode and crunched the numbers, and tweeted that the results were valid.
In the days that followed, there was considerable debate about the validity of Apple's claims. However, nearly all of the debate really just hinged on a debate over angular resolution of the human eye, and a little more over viewing distance. They're both entirely conventions.
As you've probably discovered by now, the human eye resolution can really only be characterized in angular subtense. Hold something closer to your eye, and you can see smaller features better (in theory), move it further away, and you can't make out small spatial details. The minimum angle visible with the human eye is the angle at which features (for the most common definition, a black and white square wave) stop being visible, and are indistinguishable from each other.
Most measures of visual acuity test with this implicitly - the Snellen eye chart's use of the capital "E" is literally a perfect example, which has given rise to a "tumbling E" eye chart. At twenty feet, the capital E subtends 5 minutes of arc, and conveniently has five half cycles of white to black (from top to bottom). So 20/20 implicitly implies an angular resolution of 1 arcminute (1/60 degrees).
As an Optical Sciences and Engineering undergrad, I've had 1 arcminute drilled into my head more times than I can count as being the "normal" angular resolution of the human eye system. In practice, this is 20/20 vision, which is "normal," yet not perhaps the absolute maximum for human perfection. We can play games of course and argue that a small subset of the population has better than normal uncorrected vision, and thus an angular resolution of below 1 arcminute. I have above average uncorrected vision, which I've measured to be 20/15 on average, giving an angular resolution of approximately 0.75 arcminutes. Of course, the definitions stem from the spacing of cones in the fovea, the highest resolution part of the retina.
The other informational quantity needed to test the Retina Display claims is viewing distance. Again, there's a commonly agreed upon convention - standard viewing distance is considered to be 1 foot. This is another drilled into my brain number tossed around for comfortable viewing and reading. In practice, you can focus on objects much closer to your eye - this is called the near point and is often given as 10 inches, though as you get closer you increase strain aren't likely to keep it here.
Maybe not exactly the limit, but close enough.
Given the two most common standards tossed around, 1 arcminute and 12 inches, do the math out and you'll arrive at around 286 pixels per inch as the limit for eye resolving power, comfortably below the 326 on the Retina Display. Move to 0.75 arcminutes at 12 inches, and it's 382 pixels per inch, higher than the Retina Display. Honestly, I can't see the pixels at 12 inches.
Of course, the real story is even more complicated. Remember how the definition comes with the implicit assumption that we're dealing with a square wave pattern from white to black? That's a factor too - the contrast of the two pixels. Lower the contrast, and the eye's ability to pick out features decreases even more. So far, everything we've talked about has been first order, and without aberrations. Toss in spherical and astigmatism, two aberrations common to the eye system, and eye performance drops way more.
The human eye system is actually pretty poor, and shockingly easy to outresolve. In fact, if you saw the image your eye forms on your retina, you'd likely be appalled; it's your brain that makes the system usable. But at the end of the day, Apple's claims that the display outresolves the human eye are good enough for us.
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Lemurion - Friday, July 2, 2010 - link
I was disappointed that you they only compared the iPhone 4 screen to the 800 by 480 AMOLED screens on some of the Android devices. As far as I know, all those devices use the Pentile system, which reduces the crispness of text.I would have really liked to compare the new Apple screen to the Motorola Droid's 266 PPI screen and see how noticeable the difference there was.
Matt Campbell - Friday, July 2, 2010 - link
Nice investigation work on the signal strength. Just wanted to point out that AnandTech is cited in the Apple iPhone 4 software fix story on CNN today. http://www.cnn.com/2010/TECH/mobile/07/02/apple.ip...Bad Bimr - Friday, July 2, 2010 - link
http://www.cnn DOT com/2010/TECH/mobile/07/02/apple.iphone.apology/index.htmlJust like apple, finally admitting a problem, pleasing the fan boys by saying it will be addressed and doing nothing to fix it. I am so glad I never jumped on the apple bandwagon.
fischerm83 - Friday, July 2, 2010 - link
So i was reading various news articles today and saw that apple finally figured out/admitted to what you guys found out earlier this week...*quote*
Now the company says its engineers have made a "stunning" discovery. Reception is poor and calls may be dropped because not only are people holding the phone wrong, but they also think they have a better signal than they do. In the statement, Apple says that it has made a mistake in the formula that calculates the number of bars that display the signal strength on all of its iPhones.
"We were stunned to find that the formula we use to calculate how many bars of signal strength to display is totally wrong," it said in a statement.
*quote*
Full Article:
http://news.cnet.com/8301-30686_3-20009564-266.htm...
Nice work guys, keep up the amazing work!
anandreader - Friday, July 2, 2010 - link
Brian-I'm confused as to what had to happen to get Fieldtest onto the iphone 4. Understood the bit about jailbreaking the iphone3 but didn't understand how that information got transfered to the 4.
Could you elaborate a bit there?
Per Grenerfors - Friday, July 2, 2010 - link
Thanks for the great review, AnandTech.In countries where 3G coverages isn't spotty like a teenagers face, the whole antenna/at&t/verizon debate is just utterly unnecessary.
Apple is the only brand name in tech today that's recognized by the broader public. Their products therefore make a big splash in the media when they hit the market. But the bigger splash you make, the more mud comes floating up from the bottom. Like people complaining with a spec sheet in hand without ever having seen the device in real life. Or just plain old haters. This is the downside to fame. But I'm sure Apple's laughing all the way to the bank.
Stokestack - Friday, July 2, 2010 - link
A case isn't an acceptable workaround for this. I don't buy a thin phone to bulk it up and junk it up with a cheesy case or add-on of any kind.While I'm not planning on getting an iPhone 4, if I had one and wanted to keep it I'd try to spray a coating onto the antenna band. I'd mask the front & back, the buttons, and any seams, then spray with polyurethane or something. While it would be microscopically thin, there's be no direct contact with skin. And really, that's what you said you expected Apple to have done anyway. Let's see if it would work.
Excellent review. The hack to get the numeric signal strength rocks.
Fulle - Friday, July 2, 2010 - link
Thank you for the review. It was useful to be able to look at something that was detailed, and included facts, good and bad, without a ridiculous amount of bias. It's obvious that Anand likes, or at least really wants to like most Apple products, but it was nice that that didn't get in the way of the review.The new iPhone seems to be an OK device that's on par with new Android smartphones in way of hardware... The screen's got 20% higher pixel density than the Droid, but 50% worse contrast ratio, and worse black quality... Java performance is clearly inferior to a Nexus One, but browsing performance is competitive (I'd say good, but I think all handsets have shit browser performance). Its sleak and thin, but it has no hardware qwerty. The 5MP camera produces low noise, but, the white balance is messed up, making it overall inferior to the camera in a Nexus One or HTC Incredible (or Moto Droid, even, IMHO... screwed up over-saturated colors with bad white balance are a big deal to me). Overall, it's an average device when put up against worthy competition (EVO4G, DroidX, HTC Incredible, Nexus One, or even a Moto Droid).
But, that's before you have to deal with the obvious design flaws. Glass panels on both sides? WTF? Uninsulated external antenna? These aren't minor flaws here.
So, overall I'd say that the new iPhone is inferior to at least 6 Android smartphones.... and at first I grin at that... but then I'm disappointed and mad. Apple has helped make the smartphone market the competitive environment it is today, and when they drop the ball like this, it means that other venders don't have to raise the quality of their devices to compete. It's just fortunate that Android has so many hardware OEMs, like HTC, Samsung, and Motorolla, all competing with each other... or else I'd be afraid the only thing the iPhone4 would push in competition is a higher ppi on the screens.
Lets hope this helps push the Cortex-A9 equipped Android's this winter to include higher resolution in their displays... but, man, I'm disappointed with this device.
tgibbs - Friday, July 2, 2010 - link
Does zero dB represent a standard absolute signal strength or is it an arbitrary reference value that will differ for different phones?navderek - Saturday, July 3, 2010 - link
The signal is actually measured in dBm which means it is a reference to 1mW of power.For example -30dBm = 1000 times less that 1mW = 1uW
1 microwatt does not seem like much, but actually this is a very strong signal for the mobile and you would rarely have that much power arriving at your handset from the tower. In good conditions, close to the tower or serving antenna with minimal obstructions you could expect about -50 to -60 dBm (-60dBm = 1nW (nanowatt). The system is designed to deal with such small signals...this is why I laugh when people are worried about cell tower "radiation" when actually 5 min. in the sun is a bazzillion times more radiation than what's coming out of a tower....cellular towers that is, broadcast radio towers or paging systems are another story!
But I digress...to answer your question simply, zero dBm simple equals 1mW.
Zero dBm signifies that there is no difference in ratio from the reference of 1mW.