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
Welcome to 2010, Apple Upgrades its Camera
The iPhone 4 is equipped with two cameras: a 5 megapixel camera with LED flash on the back of the phone and a VGA camera with no flash on the front. The LED flash works in both still and video modes. Like the EVO 4G, the iPhone 4‘s flash allows you to shoot in perfect darkness. If you’re filming a video in low light the LED will stay illuminated while you’re recording.
Taken with the iPhone 4 in total darkness
The same unfortunately can’t be said for the front facing camera on the 4. In anything but good lighting you’re going to get noise. It’s really only useful for FaceTime (or as an alternative to a mirror) and even then you need to be well lit for it to look decent.
Apple has opted for a 5 megapixel OmniVision sensor for the rear camera on the iPhone 4. What's interesting is that Apple has decided to bring backside illumination front and center with their marketing.
Backside illumination improves the sensitivity of CMOS and CCD detectors by reducing the amount of material in the path of incident light. In a frontside illuminated detector, a considerable amount of light is lost due to absorption that doesn't result in emission of an electron, in addition to reflection off pixel structures and electrical components near the frontside surface. Backside illumination greatly improves sensitivity by flipping the stack over. Instead of light having to pass through and possibly be reflected by metal structures, it is converted into electrons and read out by passing solely through silicon. Creating a backside illuminated part isn't as simple as flipping a sensor over, however, as manufacturers also generally thin the silicon light has to pass through before it can reach the photodiode. This further improves sensitivity and is generally accomplished through chemical etching in acid or by lapping (physically grinding) sensors at wafer scale.
OmniVision OV5650 - iPhone 4's rear camera SoC
Though backside illumination (BSI) improves quantum efficiency (how many photons are converted into electons), backside illumination is hugely important for another serious reason as well. Because the sensor is small at 4.6 mm by 3.4 mm, pixel size is also extremely small at just 1.75 microns square for the OV5650 in the iPhone 4 (state of the art sensors are 1.4 microns square, like those in the HTC Incredible's 8 MP sensor). Frontside illuminated parts generally have in the neighborhood of 10-15 microns of silicon before the active region of the photodiode where one wants photons to get converted to electrons. The result is that without backside illumination, pixels have a 10:1 ratio of height to length, you can visualize them as looking something like long square pillars. But that's a problem.
As photons are converted into electrons in that silicon, there's no guarantee that it will immediately travel down into the gate structure below to be read out by the camera. Electrons drift as they descend these columns, meaning that photons incident on one pixel don't necessarily map to the gate below. Because the smartphone camera sensors are so small, with a 10:1 ratio of height to size, the result is large amounts of so-called quantum blurring from electrons traveling into the gate structures of adjacent pixels. The result is a blurry image (and a decrease in MTF at the sensor level!), thus not representing the image that used to be incident on the sensor.
OmniVision and other smartphone CMOS sensor manufacturers thin that column down in an effort to come closer to having the pixel look more like a cube than a huge pillar. Ballpark numbers are between 3 and 6 microns, down from 10-15. The result is much more sensitive sensors that are higher resolution. While megapixels don't necessarily matter, neither does pixel size as much anymore; it's all about quantum efficiency, which is what engineers really care about.
OmniVision BSI - Courtesy OmniVision
The optical system of the iPhone 4 is difficult to characterize without disassembly, though the focal length is a bit shorter than previous iPhones. The result is that the photos are demonstrably wider angle. Backside illumination also allows for a bigger chief ray angle, higher numerical aperture (and thus lower f/#), but I won't bore you with the details.
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MacTheSpoon - Wednesday, June 30, 2010 - link
Hi, thanks for a really great review (I hope this isn't a double post, I had a problem when I submitted this before). I especially liked the hard numbers you used to measure things. Seeing the screen black levels, brightness, and contrast, plus how they compared to other phones, was really wonderful. I did have a few questions:1. Are you sure it's reasonable to conclude the maximum drop in signal strength when holding the phone is 24 dB? Doesn't skin capacitance vary from person to person? Also, I've seen some people put keys on their phones to connect the two antenna and demonstrate the reception problem, and I wonder if you could consider measuring the dB effect for that as well. Considering that keys are often kept in pockets with cellphones and could rest against the phones it seems like a reasonable scenario to explore.
2. Did you mention the problems people have had with the glass shattering easily? I've read many reports of this online. I didn't notice it but perhaps I did not read closely enough.
3. Since a case is, as you say, a must-have accessory for the phone, not only for the antenna but also apparently for the brittle enclosure, it seems unfair to give the phone credit for being 9.3 mm thin. Could you please give the thickness of the phone with the bumper? That seems to be its real thickness to me, honestly.
Thanks again for the review!
PhilBrandn - Wednesday, June 30, 2010 - link
See this video:http://vimeo.com/12951893
Even replicating the problem doesn't seem to force a dropped call.
MacTheSpoon - Wednesday, June 30, 2010 - link
It does, actually. Check this out:http://www.youtube.com/watch?v=03PQyWp0mWE
bill4 - Wednesday, June 30, 2010 - link
Cant shake the feeling of overwhelming Apple bias from most tech sites, and Anandtech.It doesn't help that it seems every tech editor's personal phone is an iPhone. And that's most certainly not because it's better, in fact in most cases the iPhone is objectively inferior to other phones.
This line in the article:
"On top of the battery life improvements Apple finally plays catch up and surpasses the technological advancements in its Android competitors. The 4's camera is as good as it gets today and the screen is a beauty. I don't believe this advantage will last for the lifetime of the iPhone "
Battery life is routinely massively overrated by Anand, it's simply not as important to most people as it seems to be to Anand. Charge your phone each evening and it's done. What's the big deal? Seems like the unnatural battery life obsession is just a way to give fake props to Apple in every review.
Likewise, "surpasses the technological advancements in its Android competitors. " Huh? Not hardly bud. By far the most important metric these days is screen size. Yes, it's probably not politically correct to say, I should talk about "usability" or some other subjective thing so we can pretend Apple is the winner, but it's the hard truth. Android phones have 4.3" and 4" screens aplenty. That's why I'm way more excited over the Evo, the Droid X, the Galaxy S, then a lame 3.5" iPhone revision. The iPhone 4 screen is actually (slightly) smaller than the 3GS screen (though they're both nominally 3.5" in screen area the 4 screen is smaller than the 3GS screen)! (Funny Anand never mentioned this fact once). Apple actually went BACKWARDs in this crucial area.
Then we have the weak 800mhz CPU vs the 1ghz+in many android models, etc etc.
Then we have the camera, worse in all respects to top droid phone cameras.
So in every relevant area except a currently meaningless one (resolution), the iPhone 4 objectively has worse specs than top Droid phones, already, yet Anand says it "surpasses the technological advancements in its Android competitors". OK, no bias there...
Overall, I just wish more reviews would call the 4 what it is, a small revision to the 3GS that falls short. Apple should have named it the 3GS+, it certainly doesnt deserve true succesor status. Hell, when sitting side by side, it's actually difficult to tell the 3GS and 4 apart, I guarantee no casual female (like, a Mom) could do it offhand. Your mom literally would not know which is supposed to be the "new" iPhone!
The Retina display is so much marketing BS. It's a small, typical incremental, completely non-revolutionary bump in resolution, yet dishonest tech sites are proclaiming it like it's somehow something tangibly new. More screen size would have been far more useful, the high PPI is truly almost completely useless compared to other 800X480 android phones, which are more than fine in that area as is. What's coming next Apple, 1080P on a 2.5" screen on the iPhone 5? Makes about as much sense. Screen size is objectively far, far more important than resolution on these phones, at least if they're 800X480 or above.
In the end I see another year of Apple losing share to the Droid phones, the 4 is a very minor change to the 3GS. Maybe next year Apple will do better.
I'm a good example, I'm limited to ATT, so I have few options, even though I dislike Apple, the iPhone 4 seemed like a good choice for me (only other option being the unsubsidized 529 Nexus One currently!), yet, there's just no way I'm going to settle for the no flash, small screen, iPhone 4.
kmmatney - Wednesday, June 30, 2010 - link
"And that's most certainly not because it's better, in fact in most cases the iPhone is objectively inferior to other phones."You pretty much lost your credibility right there..
About the battery life issue - it's huge - at least with people who travel a lot, like me. And I'm not about to carry an extra battery around.
JAS - Wednesday, June 30, 2010 - link
The iPhone 4 is a significantly greater upgrade over the 3GS than the 3GS was over the iPhone 3. The new A4 processor and doubling of the RAM make the iPhone 4 a noticeably faster device. Its improved camera and 720P video recording are additional noteworthy plusses.Yes, the Google Android OS is bound to be running on more smart phones than the Apple iOS by virtue of the fact that Andriod phones are available from more manufacturers and wireless carriers. The situation is not unlike the great abundance of computers that run Microsoft Windows versus the number of OS X Macintoshes in use. Only Apple sells Macs while MS Windows boxes are available from a wide range of manufacturers.
strikeback03 - Thursday, July 1, 2010 - link
Well the first phone I know of with a 4"+ screen was the HD2, but as it runs Windows Mobile that rules it out for a lot of people. In the US at least I don't think there are any 4" or bigger screens actually released other than the EVO, the Droid X doesn't come out for another few weeks and the Galaxy S class (shouldn't these have been named the Galaxy, Yamato, Enterprise...) do not have a firm release date yet.On the subject of battery life, if the phone cannot make it through your day (as he states previous iphones could not make it through his) then that can be a problem. Sure I would prefer a phone that can go 3 or 4 days without recharging, but until battery technology allows that to be pocketable I will live with lasting a full day. But if I start needing to have a charger at work and in my car just to make it through the day that is a problem. I do wish he would have some type of a more mixed battery life test though, after all I don't know anyone who is just going to sit and browse the web over 3G very often. How about a mix of (per hour) 10SMS, 3 min on voice call, 5 min web browsing, 5 min gaming, 5 min listening to music, checking email 4 times, and the rest of the time just flicking the screen on occasionally to check the time, or calendar, or a sports score, etc? How long could it last in a more general use scenario like that?
Mumrik - Friday, July 2, 2010 - link
"Battery life is routinely massively overrated by Anand"I can't get my head around why you'd ever say something like that. Having to recharge every night is a major hassle and completely unacceptable. We don't all sleep the same place every night or want to keep our chargers by the bed. Battery life is a huge issue right now as companies put more and more powerful and power consuming chips in phones while batter life suffers. It used to be normal to recharge you phone 1-2 times a week you know...
ale087 - Wednesday, June 30, 2010 - link
I see the Galaxy S as a direct competitor to the iPhone 4, the SoC has been said to be extremely similar... Please give us an in-depth review with awesome hardware info that we can't get anywhere else :-D Thanks for doing a great job as always! looking forward to that Galaxy S review ;-)navderek - Wednesday, June 30, 2010 - link
Are you really sure you know what your talking about when it comes to reviewing RF related topics? You seem to know the basics but I don't think you know enough to actually review handsets in this manner and your comments can be misleading.I work in the RF field as an RF Operations Specialist for a several large network that include iDEN, CDMA, and UMTS, as well as microwave and fiber optic transmission. Anyways this is not about me but I thought I would state this before continuing...
The signal bars do not always simply signify signal strength in decibels. For many handsets what the actually signify is signal QUALITY. This could be SNR as you mentioned in your article however it is not so simple...
For example, in an iDEN network the quality measurement is "SQE" and for a UMTS network (or as we like to call it - 3G network), the first and foremost quality measure is "CQI"
Lets use the CQI metric in UMTS for our example...CQI values will determine the coding technique used by the serving BTS (tower) which will determine how many redundant bits to send to keep the BER low as well determine which modulation scheme to use (i.e. different levels of QAM, like 64QAM in the best quality scenario).
Now I won't go into detail here about how all this works and how it's tied into the graphical representation of the bars you see on the handset but I will let you in on something...over the years those bars have become less and less reliable as a measure of signal strength and/or quality. Why? Because cellular carriers don't want clients to see less than 5 bars, so they have been pretty much rigged to display 5 bars in most situations until the signal is VERY BAD.
Finally, about your coments in regards to signal strength in decibels...-107dB is extremely
bad for a signal on any network. You stated that for voice and data that -107dB is perfectly fine...this could not be further from the truth and this is the point where the signal levels out with the noise floor. The BTS and/or UE begin to really lose communication with eachother at this level and on top of that you'll never get good data rates at such a poor signal level with UMTS for reasons stated above. At that signal level (-107dB) the BTS will be sending a ton of redundant bits with the most redundant coding technique as well as factoring down the QAM constallation in an attempt to keep the link alive. The data may still work in some cases at -107dB but your speeds will suffer GREATLY.
Please consider hiring an RF expert before making generalized RF based reviews. I highly respect your reviewing cabability and your intelligence, however I question your wisdom when you do such a review.
Thanks