Review: Nokia 808 PureView
Barney Britton | Product Reviews & Previews | Published Jul 30, 2012
When the Nokia 808 PureView was announced earlier this year its 41MP camera sensor (for a maximum output resolution of 38MP) made headlines all over the tech industry. Not only does it feature the highest-resolution sensor of any mobile phone camera, but at the time of writing, the 808 PureView features the highest-resolution sensor of any current camera outside of highly specialist (and very costly) medium format equipment.
We've been eager to gets our hands on an 808 since the phone was announced, and a loan sample finally arrived in our Seattle office recently. We've been using it ever since. Please note though that this article doesn't touch on the 808 PureView's performance as a phone. That's not what interests us. We want to see what it's like as a camera...
Key Photographic/Video Specifications
- 38MP maximum resolution (in 4:3 aspect ratio - output size: 7728 x 5368 pixels)
- 1/1.2" CMOS sensor, pixel size: 1.4um
- ISO 80-1600 (+ auto)
- Five white balance presets (including auto)
- Exposure compensation +/-4EV in 0.3EV steps
- Carl Zeiss F2.4 8.02mm lens (26mm, 16:9 | 28mm, 4:3 equiv)
- Focus range: 15cm – Infinity (throughout the zoom range)
• 5 elements, 1 group. All lens surfaces are aspherical
• One high-index, low-dispersion glass mould lens
• Mechanical shutter with neutral density filter
- 1080p HD video (up to 25Mb/s) with 4X 'lossless zoom'
- Stereo recording with Nokia Rich Recording - rated up to 140db
The Nokia 808 PureView's large CMOS sensor has 41MP total, outputting a maximum of 38MP (resolution drops to 36MP in 16:9 aspect ratio). Such a high resolution sensor would be little more than a stunt if the camera specifications aren't up to scratch, but Nokia has designed the 808 to be a serious photographic tool. As well as some pretty impressive hardware, Nokia has also included a raft of enthusiast-friendly photographic features in the 808 including manual control over white balance, ISO and exposure (via exposure compensation and bracketing). Exposure compensation is as good as it gets though, in terms of manual exposure control - the 808 does not offer PASM modes (not unsurprisingly).
The Finnish company is at pains to point out that when it comes to image capture, the 808's headline specification of 41MP is far from the whole story. In fact, one of the reasons why Nokia has incorporated such a high pixel count is to allow the 808 to produce better quality lower-resolution images (3MP, 5MP or 8MP).
While it might sound counterintuitive to shoot a 38MP camera at 3MP, it actually makes a lot of sense in a device of this type. Apart from anything else, if you are one of those people whose first reaction to this product was to scream 'you don't need 41MP in a camera phone! The world has gone mad! The sky is falling in!' in a sense you were right - most people simply don't need to capture such high-resolution images on a phone.
But what you probably do want from a cellphone camera is good image quality, decent speed and responsiveness, and wouldn't it be nice to have a zoom, too? That's what the 808's lower-resolution PureView modes are designed to allow.
Putting optical zooms into cellphone cameras is hard. Really really hard, which is why manufacturers tend to include digital zooms instead. Effectively just cropping and upsizing, conventional digital zoom kills image quality. Normally, the instinct of any serious digital photographer would be to run away from 'digital zoom' features for precisely this reason. But the 808 is very far from conventional.
|Images captured in the 808's PureView modes are created by oversampling from the sensor's full resolution. At the 808's 'native' focal length of 28mm equivalent, the oversampling ratio is 14:1 for 3MP images, compared to 8:1 for 5MP and 5:1 for 8MP.|
In Nokia's words, 'pixel oversampling combines many pixels to create a single (super) pixel'. In theory then, at 28mm (equivalent) - i.e., without any 'zoom', the camera's 3MP PureView output should give the best critical image quality, followed by 5MP, then 8MP, and then 38MP. When fully zoomed in, all four output modes will give the same pixel-level image quality, since at this point there is no oversampling going on -as incated by '1:1' in the graph above.
How much you can 'zoom' using the 808 depends on what output resolution mode you're in. If you're shooting at full resolution you can't zoom at all - you're stuck with the lens' native 28mm (equivalent) focal length. In 3MP PureView mode you get the equivalent of a 3.6X 'zoom' - this drops to roughly 3X in 5MP mode, and about 2X in 8MP mode. The table below shows four images, taken at the 'longest' extent of the 'zoom' in each of the 808's output resolution modes.
|38 MP (1X)||8 MP (~2X)||5 MP (~3X)||3 MP (~3.6X)|
Compared to today's travelzoom compacts a 3.6X zoom is nothing much to shout about, but it's better than no zoom at all or - worse - a conventional digital zoom that upsizes cropped images into mush. Even a 2X zoom in 8MP mode allows a useful degree of control over framing, as you can see from the image above.
You can view and download a PDF on Nokia's PureView technology here.
Performance and Image Quality
In use, the 808 PureView behaves much like a conventional cameraphone, purely because of its form factor. If you're used to a phone like Apple's iPhone 4S, or any recent high-end Android offering, you won't have any difficulty adjusting to the 808.
A dedicated focus/shutter button on the right side of the phone (with the screen held in the orienation shown below) acts as a shortcut to activate the camera app even when the phone is sleeping. A 'hard' press is required to open the app and wake the phone - a quick or light press will be ignored, preventing accidental operation of the camera. From sleep to image capture is roughly 2-3 seconds depending on AF acquisition time, which isn't bad at all. Unlike a lot of other smartphones with 'hard' shutter buttons, the 808's shutter release has a two-stage movement, which allows for half-pressing to focus before taking a picture.
|The 808's camera controls are well thought-out and easy to access. A 'hard' button on the upper right side of the phone (when viewed in the orientation shown here) acts as a shutter button in the conventional way - half-press for focus, full press to take a picture. An on-screen shutter release is also available - it's the aperture blades icon in the centre right of the screen in this image.
In 'Creative' mode, (shown here) you'll see a panel along the left of the screen that provides access to key modes and features including ISO sensitivity, white balance and exposure compensation. Adjusting these settings is a simple matter of scrolling and selecting by touch, but we wish the icons were a little less obscure.
With the camera app running, autofocus performance is roughly in line with my expectations from a modern compact camera - a bit of hunting in low-contrast situations, but in normal shooting conditions the 808 focusses in less than a second (usually), and almost always with unerring accuracy. Unexpectedly, the only times I had real issues with focus were when shooting pictures of people, when the face detection would very occasionally just give me a blurry image for no obvious reason. The 808's metering system is similarly, very reliable, although the match between live view brightness and final exposure can be pretty wide in especially dark and bright conditions. I've found that it's best to bracket around a little in very bright light to be sure of getting a pleasant exposure. An on-screen histogram would help a lot, but although a histogram appears when you're dialing in exposure compensation, it vanishes again when that screen is dismissed.
Shutter lag is effectively non-existent once focus has been acquired. In poor light the 808's built-in AF illuminator kicks in and does a good job of providing enough light for focusing, but in this situation focus slows to usually at least a second for accurate acquisition.
In full 38MP mode, there's a pause of roughly three seconds after taking a photograph and being able to view it or take another one. In the reduced resolution 3/5/8MP modes this delay is much shorter - roughly one second, for 8MP files. Viewing captured images is quick and easy. Like most modern smartphones, the 808 allows you to flip through captured images by swiping the screen, and double-tapping magnifies the view for critical analysis of detail and focus accuracy.
The 808 is a perfectly pleasant phone to use for taking pictures - it has more options than most, and handles reasonably well as a camera. Where it really shines though is image quality. The 808 produces without a doubt the best quality images I have ever seen from a smartphone, and in some respects challenges a lot of 'proper' cameras, too.
Full Resolution (38/36MP)
Let's start by looking at the big numbers - the 808's full resolution 38/36MP (depending on the aspect ratio) capture mode.
When examining my sample images from the 808, the only real indication that I was looking at pictures from a compact device is dynamic range - or rather the lack thereof. This is one of the very few black marks against the 808's camera, that in scenes with a moderately wide tonal range, if you expose for the midtones you will probably see some highlight clipping.
There's not much you can do about clipping, short of mounting the phone on a tripod and exposure bracketing (the 808 offers a 3/5 frame exposure bracketing feature of up to +/-4EV) or deliberately underexposing using exposure compensation, then pulling midtones up later using software. I have found that shooting in the 808's PureView modes improves dynamic range very slightly in real-world use, but clipped highlights are the 808's achilles heel at all of its four output resolutions.
Clipped highlights are a pretty common problem in images shot with cameraphones and compacts, and one that manufacturers are increasingly solving using dynamic range expansion and high dynamic range (HDR) modes. Unfortunately, the 808 PureView doesn't offer an equivalent feature.
I spoke to a Nokia representative about this, and it seems that Nokia tried to include an HDR feature in the 808, but ran into technical issues because of the huge processing bandwidth required to quickly capture then blend multiple 38MP exposures to create an HDR image. Bracketing was included in the 808's feature set to satisfy the needs of serious HDR enthusiasts who like to do their blending on a computer.
Low Light - Output Modes Compared:
For this test I put the 808 on a tripod and shot the same scene at ISO 1600 at all four of its output resolutions. Light was provided by a single low-intensity tungsten bulb, and exposure was 1/25 sec at F2.4. I used a 2 second self-timer to make sure that everything stayed sharp.
|3MP (100% Crop)||5MP (100% Crop)|
|8MP (100% Crop)||38MP (100% Crop)|
3MP PureView versus 38MP>3MP
|3MP (100% Crop)||38MP downsampled to 3MP (100% Crop)|
|3MP (100% Crop)||38MP downsampled to 3MP (100% Crop)|
So is the difference between the various output modes big enough to justify shooting at 3MP when 5, 8 and 38MP are available? On the basis of these tests I'd have to say that in my opinion no, it isn't. The most significant benefit of shooting at 3MP and 5MP has already been highlighted - namely, a greater effective 'zoom' compared to 8MP, which in turn offers greater versatility than full-resolution mode, where you can't 'zoom' at all. The 808's 5MP PureView mode is a good compromise between resolution, filesize and versatility when it comes to framing, which is probably why Nokia made it the default. As I mentioned earlier in this article, I have also noticed that clipped highlights are slightly less of a problem in the 808's PureView modes compared to full resolution, but clipping (to some degree) remains an issue in all modes.
We wouldn't normally put a cameraphone through our studio comparison test, but given its impressive specifications we wanted to see how well the 808 PureView compares to the many different cameras in our database. We shot our studio scene twice - once at the 808's full resolution of 38MP and again at 8MP, in PureView mode. We chose to showcase 8MP because it is the highest resolution PureView mode, and as such, more comparable when it comes to examining images alongside those from dedicated compact and system cameras. Click the thumbnail below to view the studio comparison (output modes are selected via the 'ISO' dropdown).
This is our standard studio scene comparison shot taken from exactly the same tripod position. Lighting: daylight simulation, >98% CRI. Crops are 100%. Ambient temperature was approximately 22°C (~72°F). The 808 PureView was positioned on a tripod, and was set to flurescent WB. Exposure was adjusted using exposure compensation and the built-in ND filter to achieve near-parity of exposure between ISO sensitivity settings.
|Click the thumbnail image above to see how the 808 PureView performs in our studio comparison scene. (opens in new window)|
Juha Alakarhu has been at Nokia since 2004, and currently holds the position of Head of Imaging technologies. We spoke to him recently near our Seattle offices about the 808 PureView.
A few weeks ago we had the opportunity to speak to Juha Alakarhu, head of imaging technologies at Nokia and someone who has been involved in the 808 PureView from its inception. As well as letting us get our grubby hands on his baby, he also let us ask some questions about the PureView technology that makes the 808 so interesting to photographers. Read our exclusive interview below.
What is wrong with current/competitive cameras on phones in your opinion?
Some of the key issues are related to low light performance or and unnatural looking images (due to heavy processing), lack of sharpness, lack of proper zoom, lack of proper flash, lack of proper audio quality in videos, or slow speed or clumsy use.
What are the benefits of the PureView technology?
The key benefits of the 808 PureView compared to conventional mobile phone cameras are:
- Wonderful sharpness and very natural 'non-processed' look without noise filtering or sharpening artifacts.
- Excellent noise and low light performance.
- You can zoom without the maximum aperture or focus distances changing.
- Blurred backgrounds when shooting closeup subjects.
- Very fast operation - you can get straight into photo mode by pressing the camera button even if the phone is locked.
- Very nice new user interface for zooming that we call 'slide zoom'.
- A high-power xenon flash.
- Full HD video with zoom, and advanced stereo audio recording.
- Powerful photographic controls in 'Creative mode'.
All of those apply to both stills and video. The zooming interface is especially useful in video. Speaking about video, we should not forget the new audio technology that we have in the product: rich recording with very high quality stereo microphones that can handle up to 140dB sound pressure. We also have Dolby Digital Plus playback via HDMI, and Dolby headphone technology.
How long have you been developing this technology?
The idea of a super high-resolution camera squeezed to a phone was born five years ago in bar in Tokyo with my boss Eero Salmelin. In the beginning we were focussed on technology development: optics, sensor, mechanics, algorithms (and tons of other details). The actual product program was started much later.
What are the challenges of putting zooms into mobile phone cameras?
Before the 808 PureView, we had been working quite a while with optical zooms, and we actually had two products with optical zoom in the market (N93 and N93i). However, there some very big challenges with optical zoom technology in mobile phones.
To make them small enough, the sensor size tends to get small, which results in bad or average image quality. Also, the optics get complex, with very many elements and two moving groups. Even if the optics design looks good on paper, manufacturing tolerances can seriously hurt its performance in actual use.
|The Nokia N93 was released in 2006 and featured a 3MP camera and 3X optical zoom.|
Another issue is aperture - the F number at the lens' tele position would be pretty small. This would reduce the low light performance, obviously, but would also reduce the sharpness due to diffraction. Another issue is that the exposure times might get too long, causing a lot of blurry images due to handshake.
The 808 PureView camera solves all those problems: we can use a very large, high quality sensor, the optics are simple and elegant which makes images extremely sharp, and because zooming isn't optical, the lens' F number stays the same throughout the zoom range. Also, the closest focussing distance stays the same throughout the zoom range for the same reason.
What challenges did you encounter in putting such a high-resolution sensor into a phone?
There were many challenges but one of the biggest was how to process all the data fast enough. Making that happen required a lot of innovation in all technology areas: optics, sensor, mechanics, image processing, algorithms… and then we had a lot of work to do, getting all of this to integrate seamlessly. You simply cannot design optics, sensor and image processing independently from each other.
How will you send the message that the 41MP sensor is for better quality images, not bigger images?
I think the easiest way to get the message of the image quality is just to see the images!
In the default mode the camera captures 5MP images, and the quality of those 5MP images is just amazing. We need to separate two things: output resolution - what is right number of megapixels for the outputting image files - and input resolution - what is the resolution of the sensor that is used to capture the image.
When we have the huge input resolution, we have a lot of advantages: oversampling improves the signal to noise ratio, dynamic range, and the output files have very natural non-processed look without signs of interpolation, sharpening or noise filtering. In addition, we can zoom without reducing the lens' maximum aperture.
Starting with a larger number of smaller photosites but outputting at a lower resolution allows us to increase the signal to noise ratio, too, too. By combining the signals from 7 neighboring diodes, you can get the same signal to noise ratio as you would from a photodiode seven times larger (if you do it right). Of course, we could have just used fewer, larger photosites, but then you would lose all the advantages of oversampling, plus the ability to zoom.
So, its not the number of megapixels, but how they are used. Why make 41MP output an option at all?
Even if the camera is 5MP in the default mode, we don’t want to limit how people use the camera.
If you capture the full resolution image, you do record the highest possible amount of details. We can envisage situations where somebody might want to use the full resolution mode for important images or for making very big prints (like the 9 meter print I mentioned earlier).
|This shot was taken at the 808's maximum resolution of 38MP.||This is a 2MP crop of the image on the left, which gets rid of the distracting foreground - 2MP is still a perfectly useable resolution for small prints and web use.|
Another advantage is having the ability to crop. I was skiing in Northern Finland recently, and I suddenly saw some reindeers. I only had a couple of seconds to get the shot. I started the camera by pressing the camera button, pointed it in the right direction, and captured a full resolution image, then cropped it down later, on a computer.
Can you give us any detail about how the oversampling works?
I cannot tell you much. But I can tell you that it happens in various steps and obviously it depends on the zoom ratio. Also, we are using a separate chip for image processing to handle the huge amount of data.
Have you been working with Microsoft on PureView?
Ha ha! We are discussing many topics with Microsoft...
Why Symbian? And will we see Pureview on future Nokia/Microsoft phones?
Nokia only announced our collaboration with Microsoft a little over a year ago. You don’t develop something like PureView in such a short time. We have already announced that our plans are to bring Pureview technologies to our future Windows Phone portfolio.
How do you think people will use this technology in the 808?
I think people will use the 808 not only because it’s the proverbial 'camera that you have with you' but because it is a really good camera! I’m an amateur photographer myself and I have been surprised how many of my 'serious' photos have been captured with the 808 PureView in the past months (rather than my bigger cameras).
The 808 PureView might also be attractive to professionals who need a high quality and durable camera as a backup to their main equipment. There can be also applications where a big professional device just does not fit due to their size or some rougher environments where you don’t want to risk something more costly.
Because of its portability, I think the 808 PureView would be great for many hobbies, like skateboarding, digiscoping, underwater (with some protective cover of course). I have actually received lots of emails from poeople all over the world with ideas for all kinds of interesting projects. Now that the product is available, I look forward to see these ideas put into practise.
What next for Nokia? Do you want to become the serious photographers' phone manufacturer?
Nokia has long heritage of producing excellent camera phones. We made our first camera phone, the 7650 ten years ago. The N90 was our first device with autofocus and Carl Zeiss optics, the N93 featured our first optical zoom in a mobile phone camera, and the N95 introduced a 1/2.5" sensor. More recently the N82 was our first cameraphone with a xenon flash, the N86 had a variable lens iris, the N8 had a 1/1.8" image sensor, and now we're introducing the 808 PureView, which introduces an even bigger sensor, and our proprietary oversampling.
It's hard to believe that all of this has happened in just ten years. Mobile imaging technology has been progressing amazingly fast in all its technology areas… and we are not stopping here!
Conclusion - Pros:
- Excellent detail resolution in all modes
- Very good image quality - detailed, colorful JPEGs
- Impressive photographic feature set - controllable ISO, WB, scene modes et al
- Generally reliable AF and metering
- Automatic white balance works well in all but the trickiest of light
- PureView allows 'zoom' without penalty in image quality
- Excellent video quality (and sound)
Conclusion - Cons:
- Highlight clipping problematic in scenes with wide tonal range
- No automatic HDR/dynamic range expansion function (but bracketing is available)
- Metering can be rather wayward in bright light
- On-screen histogram only available while exposure compensation dialog is open
- Interface somewhat dense in 'creative' mode
- Obscure on-screen icons for ND filter and white balance in creative mode
- On-screen ISO indication just shows 'M' when any setting other than Auto is selected
- Non-optical 'zooming' doesn't allow control over depth of field
- No image stabilization in still capture mode
- Red-eye can be an issue in flash shots (but red-eye reduction works well)
Essentially, what I've aimed to do in this article is to provide an overview of the Nokia 808 PureView as a camera, rather than as a phone, with the emphasis mainly on its still image quality. But it's not quite that simple, since inevitably, I'm judging the 808's camera in the context of its inclusion in a phone.
With this in mind, considering the 808 is still a phone first and a camera second, it's pretty impressive. The user interface is a little fussy (I'd prefer less obscure icons for ISO and white balance on the left-hand control panel, for one thing, and a proper live histogram would be useful) but it doesn't take too long to get used to. I don't much like the Symbian 'way of doing things' but I recognise that this is as much about my unfamiliarity with the operating system as much as it is about the weaknesses of Symbian itself.
In PureView mode, zooming in and out using vertical swipes soon becomes second nature. I'm an iPhone user normally, but zooming with the iPhone's pinch gesture has never felt natural to me (admittedly there is also a tiny zoom 'bar' on the iPhone too, but it's very fiddly). But more importantly, when you zoom in on the 808, you don't have to pay a huge penalty in image quality. Because images aren't upscaled, pixel-level image quality at the extent of the 808's 'zoom' in any given PureView mode is basically the same as it is at 38MP, which is to say that it's not bad at all.
For the majority of shooting situations, the 808's method of simulating an optical zoom works very well, allowing for a degree of flexibility over framing that is simply impossible when taking pictures with other smartphones. While you can get a degree of background blur in images from the 808, its actual (as opposed to effective) focal length of 8mm means you have to position your subject very close to the lens to see it. This isn't always possible (and with portraits, rarely flattering).
This is one area where an optical zoom would offer an advantage. If the 808 had a 3.6X optical zoom, even assuming its maximum aperture closed down to F5.6 or F8, depth of field at the long end, at the same subject-to-camera distance would be considerably less than at wideangle (note that the 808's hyperfocal focussing distance is approximately 2.4 meters).
The only major issue that I have with the 808's is highlight clipping. Blown-out highlights are very obvious in scenes with a wide tonal range, and this first-generation PureView phone doesn't offer an equivalent to the 'automatic' dynamic-range expansion and HDR functions that are becoming commonplace on other smartphones and compact cameras. In virtually every other respect, the 808 gives excellent image quality considering the type of device that it is. Pixel-level detail is high at low ISO settings and acceptable even at ISO 1600 for non-critical applications. In terms of sharpness and detail, the 808 is more than a match at low ISO settings for most compact cameras (and some DSLRs).
The Final Word
There are inexpensive compact cameras that offer more photographer-friendly features than the 808, but as a cameraphone, the Nokia blows its competition out of the water, and significantly narrows the gap between dedicated cameras and portable communications devices to the point where ultimate convergence seems all but inevitable (and probably sooner than some commentators had realised).
Nokia didn't release the 808 PureView in the hope of making much of a dent in the smartphone market - the Symbian operating system is obsolete, and Nokia's future plans are focussed on Microsoft's Windows Phone OS. If you want an 808 in the USA, you'll have to pay full price ($699) since no carrier (to date) is subsidizing the hardware through contracts on this side of the Atlantic. But while the Nokia 808 might not be an iPhone or Samsung Galaxy killer, it is a fascinating and compelling product, and one that has added a definite shine to Nokia's reputation in the tech industry, which was looking a little tarnished, to say the least.
The 808 proves that Nokia can innovate, and its PureView technology has piqued the interest of serious photographers, being one of the most important innovations - arguable the most important - in mobile photography since the smarphone era dawned five or so years ago. As such, the 808 is intriguing not just in itself, but because of what it represents. Things could be about to get interesting...
- Damian Dinning of Nokia responds to our 808 PureView review
- Nokia 808 PureView announcement
- Concert Footage from Nokia 808 PureView
- How Smartphones are Changing Photography
- How the iPhone Changed my Photography
There are 35 images in the Nokia PureView 808 samples gallery. Please do not reproduce any of these images on a website or any newsletter / magazine without prior permission (see our copyright page). We make the originals available for private users to download to their own machines for personal examination or printing (in conjunction with this review), we do so in good faith, please don't abuse it.
Unless otherwise noted images taken with no particular settings at full resolution. A reduced size image (within 1024 x 1024 bounds) is provided to be more easily viewed in your browser. As always the original untouched image is available by clicking on this reduced image.
|Nokia PureView 808 samples gallery - Posted 30th July 2012|
Sample Video 1
This video shows the 808's impressive digital zoom feature in video. Zooming is achieved in the same way as it is in stills, by swiping vertically on the screen. Weirdly though, the footage only 'zooms in' when you release your finger, having achieved the desired framing. It takes a bit of getting used to, and means that it isn't possible to zoom in smoothly or slowly. Zooming out, however, works as you'd expect, with the framing following your finger movement.
Sample Video 2
This video clip was taken at the extend of the 808's 'zoom', handheld, and shows how effective its digital image stabilization is at cancelling out camera shake. Footage is nice and detailed.