Tuesday, September 10, 2013

Launch Review: iPhone 5s Camera First Impressions

It's that time of the year again... new iPhone, and in what seems to be a trend, even more emphasis on photography.

The iPhone 5S Camera

  • Still 8mp, like last iSight Camera. 5-element design
  • 15% larger area
  • f/2.2 aperture
  • 1.2μm photodiode size
  • 15 zone AF matrix metering - not what you think it is.
  • Dynamic local tone map  
  • Digital Image stabilization by burst mode
  • New "True Tone" flash - flash changes colour output depending on ambient white balance
  • 10 fps burst capture
  • 120 fps - Slow motion video. 

No real surprises here except that they resisted the urge to increase the megapixel count. There a lot of improvements, but not a radical change of direction like moving to a larger sensor. A 15% increase is a nice-to-have improvement, but will just be on the edge of imperceptibility if you pixel-peep.(Remember, you have to double the area to achieve one EV of difference and despite what Apple's promotional videos would have you believe, 1.5 microns is still minuscule by camera standards.) Combined with the move from f/2.4 to f/2.2, I would guess that there is a theoretical advantage of about 1/2 stop in total of low light ability. Though not announced at press time, considering that the overall dimensions of the phone have not changed (it looks like the same or similar case to the 5 and is still only 7.6mm thick), one can assume that the field of view of the phone has not changed much (though it did slightly between the 4 and 4s generations). For reference, that would correspond to approximately the equivalent of  28mm on full frame.

It remains to be seen if the new camera processing works better in real life than it did for the 4s and 5. Traditionally, the iPhone exposure metering works like a spot meter weighted towards whatever you are focused on. There are apps out there that let you adjust focus and exposure separately, but what they are doing is essentially running the the default spot-meter routine twice. That's why (until now) apps that let you manually control exposure also tended to run slower than the default camera; the developers didn't have access to the lower level function of the camera. Looking forward to seeing if there is an improvement in the 5s default camera, and if it cuts into the business model of the third-party app developers.

The "image stabilization" is image stabilization not as we know it, but essentially an automated version of "spray and pray". Many people were hoping for optical image stabilization, but given the constraints of the depth of the iPhone body, there isn't any feasible way at present to incorporate this without making the overall phone thicker. The type of image stabilization that the 5s uses is only mildly effective, as it can't stabilize the image during an exposure as a true system would. However, what is innovate is that Apple is touting that he system is automatic. So in other words,not as good as the real thing, but at least there is no extra complexity on the user interface side. Apple is also deliberating mixing up terms by calling their best shot selector "Autofocus matrix metering", which will confuse the heck out of anybody who uses matrix exposure metering on a dedicated camera.

Speaking of true-image stabilization, there is a kind of digital image stabilization that many people are hoping for, but which the technology seems to be not up to snuff yet. This would be motion-detection assisted image stabilization. The idea is that because the iPhone has an accelerometer and position sensor (newly packaged in the M7 chip), it can theoretically track the phone's movement during the exposure time. Using this vector data, it would be theoretically be possible to reconstruct a "still" image out of a capture. The problem is that early versions of this technology (seen elsewhere) tended to produce disappointing results. Some early examples were remarkable at reconstructing blurred images, but for the most part, you could do just the same with careful application of unsharp masking.

The "True Tone" flash is an interesting idea to reduce the blue/harsh white cast of a conventional LED system. It would be interesting to see how this works in real life, as it is a real-life improvement. The problem with phone cameras is that their target audience is reluctant to use the flash because of how the pictures look. DSLR's and serious cameras have eliminated this problem by simply eliminating the flash; they've pushed the ISO capability to the point where you can go flash-less for many situations. You don't have that kind of leeway for a smartphone, and I'm glad that somebody looked at the real problem that consumers were facing; not that flash illumination is bad in of itself, but that flash images didn't look nice until now. However, the same basic limitations apply; the flash works well for filling in the shadows  people's faces at "social" subject distances; it will still be worse at illuminating a large area, such as a room or a large group of people.

Would Anyone be Brave Enough to Do This:

Coming back to pixel count: one wonders why not make a camera that is just 1920×1080 (2mp, the dimensions of 1080p capture) if the small size of the camera system constrains the quality of the optics? Ignoring the details, a 2mp sensor results in photodiodes that are 4 times are large as those in a 8mp sensor, meaning that they would have 2 stops improvement of dynamic range and image noise quality. For the sake of argument, if the iPhone went this route, it would have photodiodes 6µm in size... or roughly the same as a Nikon D600! The HTC One went this route with their UltraPixel setup. It uses the same sized-sensor as the iPhone 5, but at only 4mp, it has a theoretical one-stop advantage in low light. As well, because the pixels are larger relative to the lens, the glass "doesn't have to work as hard". The results are that the HTC one pretty much exceeds every other smartphone camera on the market. So why not go this route? This is a case of marketing trumping consumer benefits. Selling a better 4mp camera over your 8mp competitor requires more consumer education, and marketing departments tend to go for the low hanging fruit of "bigger is better". Your average HTC One user might be more well read and knowledgeable, but the iPhone and Galaxy S are mass market consumer devices. The second reason is for cropping. Serious photographers tend to frame as they intend the picture output to be, but most casual users frame loosely and crop into a picture. (If you use Instagram, you are always cropping into a picture.) You can crop into an HTC One image as well, but with extra pixels comes extra sampling, which reduces some of the jaggedness of cropping into lower resolution images. The third reason for sticking with more pixels at the sacrifice of outright image quality is because the Apple ecosystem is now built around Retina displays. For consistency, the iPhone (and iPad) camera need to output at higher resolutions in order to justify their place as "Retina" devices. (Hint: The iPad Mini probably won't be moving to a Retina screen without also changing its back-facing camera from 5mp to 8mp as well). However, photographically speaking, the UltraPixel route is the way that all phone cameras should be, but explaining to your average non-camera enthusiast that you can have better image quality of significantly less pixels is a tough sell.

How We Got Here:  A Brief History

The iPhone 4s was something of a demarcation in smartphone photography. In the transition between the 4 and the 4s, the camera unit moved to a Sony-sourced back side illumination (BSI), as did a number of other competing smartphones. This basically brought the phone camera quality almost up to par with what was available in dedicated compact cameras, so much so that for the majority of people, the iPhone 4s (and others like it) were "good enough".... which is is often uttered by camera geeks as if it were a pejorative. If the light is right (bright, but not too bright, not too much dynamic range and if the focus point isn't more than 10 feet away), BSI-sensor smart phones produce image quality that is the equal of any similarly spec'd small-sensor compact.

However, for most applications that smartphone cameras are used for (Facebook, Twitter, Instagram, Pintrest, Vine, etc.) the display size hides the pixel-mush that you see with iPhone pictures viewed at full size. That's the beauty of down-sampling images: you are taking a big set of data and truncating it into a smaller space. The result is that you have a small set of data that is richer than if you had just captured the data at the smaller size. Even though the iPhone camera is optically limited by diffraction, there are still gains to be had in downsizing; you go from a larger mushier looking image to a smaller crispy looking when viewed at 100%.

In the transition between the 4s and 5, a number of things changed, but not necessarily for the better. Many people, upon picking up the 5, perceived an immediate "improvement" over the 4s only to discover that the files didn't look that different once downloaded onto a computer. The camera hadn't changed, but the screen had; compared to the 4s, the 5 renders colours with deeper saturation and contrast. Though, I prefer the the slightly more natural appearance of photos on the 4s, the 5 has a more consumer-friendly crowd-pleasing "pop." This is a bit telling, as we have long since past the point when the majority of people stopped printing out their pictures, and we may not be entering the age of when people stop downloading them off of their phones. However, the image quality did change slightly; for the worse if you are an enthusiast. Compared to the 4s, JPEG's from the 5 appear to have more noise suppression added. Again, consumer-friendly, but fine-detail that gets picked up by the 4s tends to be smoothed over on the 5.

Another debatable "improvement" of the iPhone 5 was the synthetic sapphire camera lens front element.  Sapphire is harder than glass, and is therefore more scratch resistant. There`s no mention at launch time on whether or not the 5s uses the same construction, but since they are carrying on with the same emphasis on aesthetics and the use of sapphire in the new Touch ID home button, it's a safe bet that the camera hasn't changed. Synthetic sapphire is used on high end watches like Rolexes and Omegas, where as mass-market wristwatches by Seiko and Citizen tend to use conventional glass (aka "mineral glass") The downside is that sapphire is also less resistant to shattering. It's not used often in the mainstream camera world; almost never for lenses, but Leica does use it for some of their LCD display screens. The switch to this material may have had some unintended consequences, as the iPhone 5 proved to be more prone to producing "purple haze" on its image output when shot into bright light sources. This was a bit of excess on the part of Apple, as the camera lens, though exposed, is still a small area that wouldn't ordinarily pick up scratches. Fine scratches from extended wear wouldn't have much, if any, impact on the final image quality, and anybody abusing the phone enough to gouge or crack the lens likely would have damaged some of the other internals as well. It seemed like a bit of hubris on the part of Apple at the time, especially considering how much of the 2012 launch was devoted to the aesthetics of the phone's manufacturing... so much so that Samsung parodied it in their Galaxy SIII commercials. Hopefully they've worked on the lens coatings to reduce this; it would be very un-Apple-like to let this problem carry over for another generation.

Physical Limitations, Not Technological Ones

We're now at the stage where savvy phone users are becoming quite aware of what they want out of a  smartphone camera... a lot of it is the same they that traditional camera users want... better ISO capabilities, higher dynamic range, lower noise. The problem is that the camera is still housed in something that functions as a phone, so there are physical limits to how much improvement can be squeezed out of the current technology. Going to a larger sensor improves all of these qualities, but also makes the phone larger and deeper. Small also has one advantage when it comes to focusing, as you can see here:

As depicted by the graph above, with a 1/3.2" sized sensor, focus precision is only critical within two feet of the camera. After that, the near focus limit is already quite close to the hyperfocal distance, and the far focus limit zooms off to infinity just after 3 feet. 

The iPhone 4s, 5 and Galaxy SIII total sensor size correspond to approximately 15.4mm². The Nokia 808 uses a 1/1.2" sized sensor which weighs in 85.4mm². That's a significant improvement in image quality, but it also comes at the expense of increasing the bulk of the phone. The Nokia 808 is 13.9mm thick, whereas the iPhone 5 is just over 1/2 as thick at 7.6mm. To put that in perspective, the iPhone sensor area weighs in at 2% of that of a full-frame DSLR like the Nikon D800. Clearly, smart phones weren't meant to do professional photographic work. However, s smartphone camera sensor is only half the size of the 1/2.3" sized sensors used in lower end compacts and superzooms. That means that theoretically, at the same pixel count, an iPhone would only be 1 stop worse than a dedicated compact camera through its ISO range. If you compare the iPhone 4s and 5 versus a non-BSI 1/2.3" compact, the differences shrink further.

The other physical limitation is diffraction. Both the new and old iPhone operate very close to the diffraction limit, the point where the so-called "airy-disc" of a point of light is larger than than the size of the photodiode capturing it. Compared to a dedicated camera, the individual pixels of an iPhone image are never going to to be as crisp; once again, this is a physical limitation, not a technological one. No amount of image processing or camera advances can change that.

Conclusions and Looking Ahead

The iPhone 5C is a bit of consolidation for Apple, essentially an iPhone 5 wrapped in a less expensive polycarbonate body. Consolidation is the key word; even though the 4s will live on as the cheapest iPhone in the lineup, Apple will eventually transition all of their phones to the 16:9 form factor, thereby ameliorating the dreaded "fragmentation" of screen sizes and aspect ration that Android developers have to deal with.

"If you like it then you shoulda put a ring on it."

Aside from the camera improvements, the big selling feature for 2013 is the Touch ID fingerprint scanner integrated into the home button. As a photographer, I like this feature because I have my phone key-pad locked. If I want to use a camera app for a spur-of-the-moment picture, the default app can be accessed quickly from the lock-screen in iOS6. The problem is in accessing the more full-featured camera apps; that requires keying in the pass-code and in the extra time that requires, the moment might have passed by.

Time Now for the Traditional Annual Rant

Last year, the iPhone 5 launch seemed more subdued than the the previous launch, showing how much the smartphone market had matured over the years. Partly driven by the lock-in of carrier subsidies, it only makes sense to skip generations (just like cameras), and for many people skipping two generations is not all that distasteful. Considering how well received the 4s was, it is probably (but not a given) that the 5s will be once again a bigger success than the 5. This will be because of the group of people coming off of their contracts (iPhone 4s). However, myself, and it seems quite a few people already, are not feeling the love for the 5s pricing. Yes, there are a lot of new features, but given that the launch price remains (relatively) consistent from year to year, its a disappointment that the memory tiers are also the same. The entry level 5s is still 16gb, bringing up the inevitable complaints about how Apple is ripping people off on the price of internal memory. To move to 32gb requires $100 USD extra on the unsubsidized price scheme, which is way out of line compared to any other form of flash memory that you can purchase. I find that 16gb right now is just about the minimum for "enthusiastic" use... there's just enough memory for apps and music with some left over for pictures and videos, but you are still snuffling stuff on and off the phone all of the time. 32gb gives you more breathing room. The argument is that microSD's are "old tech" and that we have things like iCloud and Dropbox now. I see three problems with that arguement:

  • It's still glossing over the fact that the incremental price increase is out of line with the actual cost of the memory. Apple gets away with this because the rest of the phone is desirable enough to overcome this point, but it is a serious consumer friction. The problem with cloud storage is that when done poorly, the new benefits don't always outweigh the existing benefits that people have enjoyed. The microSD card is the poster child for this: just when SD cards became cheap and ubiquitous, the commercial powers that be started pulling consumers away from that towards locked-in proprietary systems. If you think that the cloud is the way to go, just put your iPhone/iPad next to your camera and ask why you can't easily transfer images...when the data is sitting mere inches away.
  • If Apple wants to do more business in China, they are going to face a a consumer base that is doubly skeptical of proprietary memory devices. China is the land of 1000 Android clones, all of which let the user upgrade memory cheaply.
  • In the wake of the Edward Snowden/NSA scandal of 2013, I think a higher proportion of the population is now more skeptical than ever of leaving their information with a third party. Facebook and Instagram haven't exactly been good corporate citizens when it comes to privacy issues, but the game is different when the distrust moves from a commercial entity to the government.

However, most of the improvements to the the iPhone's camera system further accelerate it into the arena of cannibalizing the traditional low-end compact camera. This is so much the case that the annual release of a new iPhone is now a bigger camera announcement than anything than anything from the likes of Nikon, Canon or Olympus. Sobering thought for the camera industry, and especially for Nikon considering how dependant they've been on traditional compact camera sales in recent years.

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