One of the things we think Apple does better than other smartphone manufacturers is build great cameras into its phones. It's one of the reasons that iPhone is one of the most popular cameras in the world, period. Based on our experience, the iPhone 5S' camera produces better-looking photos than that on high-end Android phones like the Nexus 5 and HTC One M8, and it's a safe bet that the next iPhone will have yet another camera upgrade. Sony currently supplies the small CMOS camera in iPhones, and it's also the supplier of camera sensors on a variety of Android phones. The difference in photo quality between those devices, then, can partially be attributed to the lens system used. But photo quality is also tied to the imaging software built into the phone's OS. And on that front, Android may take a leap over iOS later this year.
While Apple is opening up manual camera controls to developers in iOS 8, one feature that's sorely lacking is support for RAW photo capture. And coincidentally, that's one feature that Google is bringing to Android L--support for camera apps to write raw pixel data from the camera sensor as a DNG (digital negative) file. While this may not sound like a big deal for most smartphone users, it is in fact a huge deal for photographers who are doing more than just taking photos to immediately share on social networks. As I've said before, the post-processing of a photo is just as important to the whole of the photography process as the act of snapping the shutter. The ability to save smartphone photos as RAW files instead of just JPEGs is the equivalent to an immediate and free upgrade to the camera, regardless of the sensor make.
To understand the benefits (and costs) of RAW, let's quickly go over the limitations of JPEG images. JPEG is a lossy file format, using image compression algorithms to reduce the file size of an image while retaining as much details as possible. Standard JPEG settings allow for a compression ratio of 10:1 from the original image without noticeable reduction detail, especially on small screens. JPEGs are also most commonly saved with 8-bit color profiles. That means that each of its RGB color channels top out at 256 gradiations. 256-degrees of brightness for each color channel is plenty for a photo, but camera sensors can actually record much more detail than that. Digital imaging chips can process light coming into sensors in 12 or 14-bits--light data that is lost when converting an photo to a JPEG. That extra data, when run through a RAW image processor, allows for more flexibility when editing and helps avoid image artifacts like light banding.
Another limitation to JPEGs is the inconsistency of compression engines between smartphones. The amount of compression used to save a photo in the iPhone is different than that of an Android phone, and can vary between camera apps. For example, a 13 Megapixel photo taken on the new OnePlus One Android phone is compressed to a file between 1-2MB at the highest quality setting. The iPhone 5S, using a 8MP sensor also made by Sony, saves JPEG photos that are also around 1.5MB each. (By comparison, the 14MP camera on the Phantom 2 saves 4-6MB JPEGs). So where did that extra megapixel data go? While some camera apps have JPEG quality settings, the amount of compression isn't always transparent, so you don't know if you're getting the best possible photo you can from your phone.
RAW image files eliminate that ambiguity, because it's just storing the unfiltered image data taken from the camera sensor. And the best part is that saving in RAW isn't a hardware limitation. All digital camera sensors have to pass that raw information through the phone's image processors--it's up to OS and camera software to give users a way to save that data before it gets lost in the JPEG output. The high-end Nokia Lumia phones have RAW photo capability, and previous phones like the Lumia 1020 were granted RAW file saving with a software update. DPreview ran a comparison of RAW and processed JPEG photos with the Lumia, and I ran own tests with a small-sensor camera to show you the image detail differences.
I don't have a Lumia 1520 or 1020 on hand, but found a substitute in the DJI Phantom 2 Vision+'s on-board camera, which can save RAW files. The camera sensor on the Phantom is actually sized at 1/2.3", which is the same sensor size as that on a GoPro or cheap point-and-shoot. The iPhone and most Android smartphone camera sensors are half that size at 1/3.2". They're both far smaller than APS-C-sized sensors found in Sony's mirrorless cameras and most DSLRs. And for the purposes of my testing, I wanted to see what a standard compressed JPEG looked like from this small-sensor camera compared with what the photo could look like after post-processing in Lightroom.
I took a series of photos with the Phantom at home, both outdoors and indoors, and one in very low light. Afterward, I edited the RAW photos to correct for white balance, depressed the highlights, and lifted as much detail from the shadows. The first photo below is a processed RAW photo taken outdoors:
On first glance, it doesn't look all that much better than your typical JPEG smartphone photo, and that's because the limitation is still on the physical size of the sensor, and the details don't matter as much when a photo is resized for web. But cropped in below, you can see a lot more detail in the RAW version, especially on the grass and edges of the car. (Click the images to enlarge them to their original size).
The same holds true for this indoor photo below. The text on the book spines are actually readable in the RAW photo. Something to note is that the black color on the bookshelf actually looks more uniformly back in the JPEG, and that's because the compression algorithm flattens the details out. This is an example of the algorithm making a good assumption about viewers not needing the noise detail in the black areas, but you lose the ability to pull out any of those shadow details.
The biggest benefit of RAW comes in low-light photography, as seen in this very dimly-lit shot of the kitchen below.
When cropped in to 100%, you can see just how poorly the JPEG holds details in low light images. Both photos were taken with the same ISO and exposure settings, but the RAW file just holds that much more light data than the JPEG, which can be revealed in post.
These comparisons show why RAW photography is essentially an instant upgrade to any smartphone camera. And as I mentioned earlier, the limitation is still the camera sensor size. That extra detail in a RAW file may look very grainy, so you need to massage the detail out of the file with experiments in post-processing and noise reduction. But the benefits are clear.
RAW photo capture has its costs as well. The most obvious is how much space RAW images take. On the Phantom, a photo take takes up 6MB as a JPEG will take up 30MB as a RAW file--five times the size. 30MB images add up very quickly on a smartphone. Saving in RAW also takes much more time than just saving a JPEG. It'll depend on the speed of the image processor, but on the Phantom it takes several seconds--longer than an HDR photo on the iPhone. You also then lose the ability to shoot in burst mode for rapid-fire shots.
Rendering a RAW image is also computationally intensive and slow--not ideal for mobile. That's why there are very few mobile apps that support RAW adjustments (most RAW photo editors on iOS actually just tap into an embedded JPEG preview). The best option for future Android camera apps is to give the option to save photos as both JPEG and RAW, so users can use the JPEG for mobile sharing and sync the RAW file back to desktop for editing (still hoping for Lightroom Mobile on Android).
I'm really excited about the prospect of RAW photo capture on Android L, even if it adds a layer of complexity to the mobile photography workflow. That may be why Apple may never add RAW photo capture to iOS--it's counter to the "just works" immediacy and instant gratification that users have come to expect from smartphones. And given than Apple recently announced that it has shuttered development of its Aperture program, they may be of the opinion that JPEGs are good enough for photo tweaking and posting to Instagram.
Lead photo via iFixit's Nexus 5 Teardown