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.
 |
 |
|
iPhone 3GS
|
iPhone 4
|
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.
Facebook
Twitter
RSS
270 Comments
View All Comments
The0ne - Wednesday, June 30, 2010 - link
Actually, Anand likes the performance of the iPhone and i don't blame him. It is smooth, well implemented and thus makes using it more enjoyable, quantifiable or not. Features be damn, what counts is how a user perceives the device he/she is using. And once attached or rather use to them it's hard to like something that isn't the same or better.For the most part, android OS and WebOS are fine for the vast majority of users. The slight sluggish performance is really not hindering anyone from doing anything practical. It is really just a matter of perception.
As for features and design, I can honestly say unless you been in the design phase yourself many decisions are made prior to production. Missing features such as Flash memory support is a choice left out purposely. Don't kid yourself they are doing it because they either can't or because of lack of money/resources.
mesiah - Thursday, July 1, 2010 - link
I don't agree with the flash memory support. Flash memory is so cheap to implement that it comes on the cheapest of cheap products. And before anyone uses the excuse of "a flash port would clutter up the phone and make it look ugly" Look at the huge ugly connector port used to sync / dock an iphone. Compare that to micro usb. You don't think they could shrink that thing to a quarter of its current size, or less, and add in a flash memory port? Hell, A smart engineer could make a docking port that doubles as a flash memory port (makes me wonder why we haven't seen this yet.) The reason you don't get upgradeable flash memory is the same reason you don't get removeable batteries. There isn't money in batteries and memory, the money is in forcing people with outdated hardware to upgrade.The0ne - Thursday, July 1, 2010 - link
Err, I think u might has misread what I was trying to say. As you've stated flash memory support is very easy and cheap to design in. For Apple not to have it means they have purposely decided against it. For example, creative labs has flash support on some of their PMP devices but it is extremely poor in design that it's unusable. That's the other caveat to just putting features in and not properly supporting it.Anand Lal Shimpi - Wednesday, June 30, 2010 - link
By feature parity I was referring to what's new that made it into iPhone 4: higher res screen, 45nm SoC, much improved battery life, smaller form factor. I'd expect that within the next 6 - 12 months we will see Android phones with similar specs.Software feature wise, Android is at parity in most cases and far ahead in others.
Take care,
Anand
darwinosx - Wednesday, June 30, 2010 - link
They you don't know much about either Android, the iPhone 4, or both.Mumrik - Friday, July 2, 2010 - link
Are you aware that your username undermines every single pro Apple comment you make?Also, I think most of us will take Anand's word for it over an anonymous commenter's.
mmike70 - Sunday, July 4, 2010 - link
Why does it undermine?John Sawyer - Thursday, July 1, 2010 - link
The somewhat larger number of pixels in the Retina display that Apple is using in the iPhone 4, plus its smaller size than the Evo and Droid X displays, do combine to make for a massive difference, as the pictures in the article show. I've compared the two, and the iPhone 4 display really is startlingly good. Many things don't look hugely different between the two, such as some videos, larger graphics and text, etc., but small text (which I look at a lot because that's what a lot of websites serve up) certainly does.semo - Wednesday, June 30, 2010 - link
I'm sorry Anand but I just couldn't bring my self to read your review after yet again detecting your bias towards this product. You come from an engineering background and it shows in your methods of analysis which appeals to me.Do you wait 6 hours in line for a new SSD? I detect hints of emotion in this article's introduction. I could be wrong but I always try to avoid technical reading when I suspect there is bias. It is plain to see on other technical sites where the companies' mission statement is part of the introduction but much more subtle here.
I look forward to your next SSD and chip architecture articles.
bplewis24 - Wednesday, June 30, 2010 - link
Anand is about the most objective Apple iPhone fanboy there is. There is no denying this, and it's both a compliment and a criticism. Until he can stop making subjective generalizations like this:"There is this more open, more configurable, more capable feel you get with Android that you don't with the iPhone. That can be both a positive and a negative. Android phones feel more like computers while iPhones have more of that appliance feel. It still boils down to personal preference, the 4 won't change that."
Really, Anand? Being more open and configurable can be a bad thing? We really need to stop perpetuating this myth that Androids can only be liked by "PC" geeks and people who like to dig deep into the OS. The reality is that Android devices don't force you to customize if you don't want to.
I'm also fairly certain that the "scrolling" issue which isn't present on my Moto Droid has something to do with the live wallpapers eating up CPU processing power. Nevertheless, I don't experience it on my phone and to blanketly imply that the OS UI is clunky (which most iPhone fanboys cling to in every comparison) is completely disingenuous.
Until Anand can rid himself of some of this bias, he will still be known as the best and most objective iPHone reviewer on the interwebs, but the title in and of itself won't be saying very much.
Brandon