Apple iPhone 4S: Thoroughly Reviewed
by Anand Lal Shimpi & Brian Klug on October 31, 2011 7:45 PM EST- Posted in
- Smartphones
- Apple
- Mobile
- iPhone
- iPhone 4S
Camera Improvements
Arguably the second largest hardware change (with the A5 SoC being the first and largest) in the 4S is the inclusion of a much improved 8MP camera. In case you’ve forgotten, the iPhone 4 previously included a 5 MP camera. Back when the 4 was introduced, Apple talked for the first time about backside illumination, and pixel sizes. In a later update, the camera got even better with the ability to buffer three full size images and merge to HDR in real time. This time, Apple brought up F/# and backside illumination again, and added one more thing.
Though Apple never talked about any of their optical design for the iPhone 4 camera, to the best of my knowledge the design likely was close to reference designs reported on a few lens lists consisting of four plastic elements. For the 4S, Apple has mixed things up by including its own optical design front and center, and made special note of a five plastic element design. I’ve put together a table showing the 4 and 4S in comparison based on what information is available.
Note that many have speculated that Apple is dual sourcing the CMOS sensor which seems likely, and given the sensors out there the two most likely choices are Omnivision’s OV8830 and Sony’s IMX105. Both of these have almost identical specifications, including 1.4µm pixels, a 1/3.2“ format, and an improved backside illumination process over the previous generation wafer-scale process. Omnivision’s BSI–2 process cites some specifications that seem to line up with what Apple talked about in their presentation, including better quantum efficiency (ability to convert photons into electrons), low-light sensitivity, and larger well capacity (which translates to increased dynamic range). You’ll note that the 4S uses the same sensor format as the previous generation - 1/3.2”, and includes more pixels, which results in the pixel size going down from 1.75µm to 1.4µm.
| iPhone 4 vs. 4S Cameras | ||
| Property | iPhone 4 | iPhone 4S |
| CMOS Sensor | OV5650 | OV8830/IMX105 |
| Sensor Format | 1/3.2" (4.54 x 3.42 mm) | 1/3.2" (4.54 x 3.42 mm) |
| Optical Elements | 4 Plastic | 5 Plastic |
| Pixel Size | 1.75 µm | 1.4 µm |
| Focal Length | 3.85 mm | 4.28 mm |
| Aperture | F/2.8 | F/2.4 |
| Image Capture Size | 2592 x 1936 (5 MP) | 3264 x 2448 (8 MP) |
| Average File Size | ~2.03 MB (AVG) | ~2.77 MB (AVG) |
Everybody likes talking about sensors (and I see lots of attention given to them), but any good photographer knows that it’s a combination of optical system and sensor that matters to performance. Optical design is important, and having studied as an optical engineer I find it interesting that Apple would draw attention to having a custom design of their very own with an additional plastic element. For a while I’ve held off on really talking about smartphone camera optics, but while we’re here, let’s touch briefly on them.
The iPhone 4S camera module
Thus far this generation and the one before it have primarily used 4 plastic elements, and virtually everyone but Nokia uses nothing but plastic (Nokia famously uses Zeiss-branded designs, often with glass elements). Optical design is generally driven by material availability, and there are only a few optical grade (read: transmissive in the visible) thermoplastics out there - Styrene, Polystyrene, ZEONEX, PMMA (Acrylic) and so forth - the list is actually relatively short. Thankfully polystyrene and PMMA can be used to make something of an achromatic pair, with polystyrene as a flint, and PMMA as something of a crown. Plastic provides unique constraints as well though - coatings don’t stick well, not very many have great optical properties, they have a high coefficient of thermal expansion, high index variation with temperature (which oddly decreases with increasing temperature), and less heat resistance or durability among others. With all those downsides you might wonder why smartphone vendors use plastic, and that reason is simple - they’re cheap, but more importantly, they can be molded into complicated shapes. Those complicated shapes are aspheres, which are difficult to fabricate out of glass, and afford much finer control over aberrations using fewer elements, which is an absolute necessity when working with very little package depth.
Apple's 4S versus 4 infographic
So what does adding another element get you? Well, when you’ve faced with limited material choices, adding more surfaces gives you another opportunity to balance aberrations that start blowing up rapidly as you increase F/#. That said, there are tradeoffs as well to adding surfaces - more back reflections, increased cost, and a thicker system. In the keynote, Apple notes that sharpness is improved by 30% in their new 5 element design, and MTF is what they’re undoubtably alluding to.
Genius electronic optical - 5P lens. Compare to above.
Genius electronic optical has a page on their website with a lens system that seems likely to be what’s in the 4S, as the specifications include 8 MP resolution (same size), same sensor format, F/# (2.4), 5 plastic elements (5P) and looks basically like what’s in the 4S. Other than that, however, there’s not much more that I can say about this Apple specific design without destructively taking things apart. One thing is for certain however, and it’s that Apple is getting serious about camera performance, something that other handset vendors like HTC (with its F/2.2 systems) are also doing.
Apple made mention that it also included an IR filter in the 4S optical design. If you recall back to our Kinect story, I used the 4 camera to photograph the IR laser structured light projector that Kinect uses to build a 3D picture. The 4 no doubt has an IR filter (though not a great one), but it’s probably just a thin film rather than a discrete filter right before the sensor. The 4S includes what Apple has deemed a ‘hybrid IR filter’ right on top of the sensor, which is possibly just a combination of UV/IR CUT filter (UV is a problem too), and an anti-aliasing filter.
If you try and take the same Kinect (IR source) picture with the 4S, thankfully all those non-visible, IR wavelength photons get rejected by the filter. This doesn’t sound like much until you realize that silicon is transparent in the IR and will bounce around off the metal structures inside a CMOS or CCD and create lovely diffraction effects on fancy sensors. I digress though since that’s probably not what Apple was trying to combat here. On a larger scale, IR will generally just cause undesirably incorrect color representation, and thus people stick an IR filter either in the lens somewhere or before the sensor, which is what has been done in the 4S. The thin film IR filters that smartphones have used in the past also are largely to blame for some of the color nonuniformity and color spot (magenta/green circle) issues that people have started taking note of. With these thin film IR filters, rays incident on the filter at an angle (as we move across the field) change the frequency response of the filter and the result is that infamous circular color nonuniformity. I wager the other effect is some weird combination of vignetting and the microlens array on the CMOS, but when I saw Apple make note of their improved IR filter my thoughts immediately raced to this ‘hybrid IR filter’ as being their logical cure for the infamous green circle the iPhone 4 exhibits.
Another minor difference on the 4S is that the LED flash is improved. The previous LED flash had a distinctively yellow-green hue, the LED flash on the 4S seems slightly brighter and also has a temperature that’s subjectively much closer to daylight, though I didn’t measure it directly. I habitually avoided using LED illumination on the 4 and will probably continue to do so on the 4S (and use HDR instead), but it does bear noting that the LED characteristics are improved. Unfortunately the diffuser and illumination pattern still isn’t very uniform or wide. It also seems that all this talk of moving the LED flash to the other side of the device to combat red eye turned out wrong as well.
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ados_cz - Tuesday, November 1, 2011 - link
I have the 4S now and the problem is gone but once my girlfriend comes with her 4, I will make a video and post it to prove you wrong. People have no problems only in areas where signal is really strong. Why would I possibly want to lie?wonderfield - Tuesday, November 1, 2011 - link
What's of concern here is not whether the issue (signal loss) can be demonstrated but whether the phone is, in Brian's/Anand's words, "usable" with the defect or not. It's certainly possible for the GSM iPhone 4 to be rendered unusable in a low signal strength area with a natural, right-handed grip just as it can be rendered unusable with a death grip. That's not to say the phone will be unusable in most scenarios, however, because in most scenarios the phone should function properly. There are certainly edge cases, and the issue is more significant for those who're left-handed and for those who live/work in very poor coverage areas (where it can become an issue), but, again, that's not the typical use case. It's why I categorize Brian's claim that the GSM 4 is not usable without a case as being disingenuous.Realistically, you don't need a "really strong" signal to have not have any problems with the phone, you only need a signal great enough to overcome any attenuation introduced by making contact with the antenna. The extent of the attenuation, as demonstrated in another Anandtech article to which you might refer, is not as significant as portrayed by some media outlets.
ados_cz - Tuesday, November 1, 2011 - link
As far as the need for good signal went I needed to use the case all the time otherwise I would always have to hold the phone in unnatural way. iPhone 4/S is a really beautiful piece of hardware and It was really upseting that I had to use the case and spoil the desing. My close friend living just 15 miles next to me in Perth does not use the case and when he does not care to not to hold the phone in sensitive area, the call drops. It happend to me with him on the phone on few occasions. Few of my friends at uni need to use the case for iPhone 4 as well. The problem was not overstated. Either learn to hold the phone unnaturaly avoiding joining those two critical antenna strips or use a case. I opted for a case. My friend in the London got on well without case, but he learned to hold it by the to when calling. Anyway, I am glad that I have the 4S now and I think my girlfriend does not mind the case on her (former mine) iPhone 4. It so well made piece of hardware and so affordable here in Britain. You are being ripped off in US. Check the deals for iPhones on www.three.co.uk I got mine iPhone 4 for 69 pounds 5 months ago with two years contract for 35 pounds a month (2000 mins any network, 5000 mins mine network, unlimited 3G data with no fairu user policy). I paid 189 pounds for girlfriends (now mine) 4S for 32GB white version just few days ago and she got the same 35 pounds contract.Tetracycloide - Tuesday, November 1, 2011 - link
"I have hundreds of friends who have iPhone 4's who've never had any issue with signal loss at all."Really? Name them. Numbered from one to at least two hundred if you please.
Overstating the strength of your anecdotal evidence doesn't make you look right it makes you look biased.
For what it's worth, I think you're a huge tool for, well, being such a huge tool.
doobydoo - Wednesday, November 2, 2011 - link
Don't be ridiculous.To label someone a 'tool' for stating that their friends don't have issues with signal loss on a phone, is quite frankly ironic.
To suggest I would list my friends names in a bid to convince such a low level individual is even more ridiculous than the rest of your comment (which is a lot).
If you really need hard evidence, I'd point you in the direction of the millions of iPhone customers who gave the iPhone 4 the highest satisfaction ratings of any phone, full stop. Bit hard to imagine that happening if they cant make calls on it, don't you think?
To claim I'm overstating my quite logical claim doesn't make you look right, it makes you look biased.
Tetracycloide - Wednesday, November 2, 2011 - link
I labeled you a tool because your response to another commenter saying they experienced an issue you and 'your friends' never saw was 'your a liar' or more literally "For what it's worth, I don't believe you anyway." That's where you were a tool, that part right there.Your 'hundreds' comment was absurd and you know it. To obtusely pretend I'm actually asking you for a list of names and act like that's absurd (it was obviously rhetorical) is to miss the point which was: you do not actually have 200+ individual examples from 'friends' to draw from. That's absurd.
Your claim was hardly 'logical' it was an absurdly overblown statistic that, even if it was accurate, would still be anecdotal. As are you're 'millions of iPhone customers' by the way. The phone looses signal if held incorrectly. That is the objective reality, full stop.
doobydoo - Friday, December 2, 2011 - link
How ironic that your justification for calling me a tool, is that I essentially disbelieved someone else, after that's all your comments to me are based on.Not only that, but how ridiculous and illogical to say someone is a tool for not believing something. Grow up?
'Hundreds' is not absurd at all, perhaps it sounds absurd to a social recluse? But I can actually name at least 200 friends of mine who use iPhones. Sorry if having friends is a strange concept to you. How dare you claim that you 'do not believe' my 200+ friends claim - that makes you a tool (it's a definition handed down to me by someone special).
Even if my claim was anecdotal, so what? Your criticism of my claim wasn't that it was anecdotal, and I never masqueraded it as anything other than what it was?
The 'MILLIONS' of iPhone customers is not anecdotal at all, by the way - they HAVE factually given the iPhone 4 the best user ratings of any phone of all time. That's reality, fact, pure and simple. They wouldn't do this, if they couldn't make phone calls, don't you agree?
I own an iPhone 4, and it doesn't LOSE (wtf is 'looses') signal in any meaningful way (as in, it never affects call quality or causes calls to be dropped) if held in any way I want. Unbelievable that you make such claims then try to define them as 'objective' - exactly the criticism you levy at me.
gcor - Monday, October 31, 2011 - link
Reading the specs on a lead acid 12v battery I have, I discovered that the higher the load in amps, the lower the total amp hours the battery will output. For example, the spec's say that a particular model can deliver a max of 1 amp hour over 20 hours, but only .5 amp hour over 12 hours.I'm guessing this is also true for the batteries in smartphones and laptops. This assumption seems to be supported when looking at the 3D gaming battery life results in the review, where a 10% increase in power consumption on the 4S, resulted in a 25% drop in battery life.
I assume this has implications for the "race to sleep" concept, as an increase in amp draw by the device may reduce the battery efficiency enormously, as well as actually using more power.
Anyway, just a thought to add into the mix when estimating a % speed increase required for a pay off in additional sleep.
Pliablemoose - Monday, October 31, 2011 - link
Your recommendations mirror my own thoughts, picked up 3 iP4's in the last month, 2 ATT models to put on Straight Talk for $499/year each with unlimited talk text and data (yes, I know it's not really unlimited data) for my kids, and a Verizon iP4 for me. I actually replaced a ThunderBolt with an iP4, got tired of the poorly executed radio software and the constant reboots to keep it connected. The ThunderBolt is a heck of a 4G LTE modem, sort of a poor phone, and definitely a brick with the extended battery it needs get me through a day of web surfing and stock trading.Saving my upgrade next year for an iP5, and keeping my fingers crossed for at least a 4" screen.
ltcommanderdata - Monday, October 31, 2011 - link
"Furthermore Apple even seems to be ok with combining a process shrink with a new architecture as we saw with the iPhone 3GS. It's generally thought of as a risky practice to migrate to both a new process technology and a new architecture in the same generation, although if you can pull it off the benefits are wonderful."I don't believe Apple has actually pushed a new process and architecture simultaneously. Up to now, the iPod Touch was generally the test platform for new processes as a shrink on an existing architecture.
The full evolution is:
iPhone 2G/1st gen iPod Touch/iPhone 3G 412MHz ARM11 90nm
2nd gen iPod Touch 533MHz ARM 11 65nm
iPhone 3GS 600MHz Cortex A8 65nm
3rd gen iPod Touch 600MHz Cortex A8 45nm
iPad 1/iPhone 4/4th gen Touch 1GHz/800MHz Cortex A8 45nm
iPad 2/iPhone 4S 1Ghz/800MHz Cortex A9 45nm
It is curious that we haven't seen a shrink of an existing chip as a pilot for a next gen process, either Samsung 32nm or TSMC 28nm, although the iPod Touch not being updated this year didn't leave many options. It would no doubt be too risky to put a new process pilot chip on the iPhone 4S. I believe iFixit did find some different markings on the 2011 iPod Touch, but I haven't heard about any size difference so that makes a large shrink unlikely. Is there any chance the 2011 iPod Touch could be piloting the A4 on a TSMC 40nm process as a means of getting that relationship off the ground? Is there enough commonality in the tools for the 40nm and 28nm processes to make piloting on 40nm a worthwhile interim step?