Nokia 808 Pureview

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)
• Construction:
• • 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

Features

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).

This diagram shows the size of the Nokia 808 PureView's 1/1.2" sensor in comparison to those used in various compact cameras and mobile phones. A Four Thirds sensor is included for scale.

As you can see, the 808 PureView is packing quite an impressive sensor, much larger than those found in compact cameras, and not that much smaller than the CX-format sensors used by Nikon in its 1-system and Sony's recently-announced Cyber-shot RX100.

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.

PureView (3/5/8MP)

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.

PureView 'Zoom'

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.