A photographer's Perspective with Nokia 808 PureView Review

While there's no question that the Nokia 808 PureView is technologically interesting and represents something of a breakthrough in photographic technology, at the end of the day it's still only a phone camera, just one with a larger than average sensor. Yes, the images can be amazingly detailed at full resolution, and yes the "oversampled" images do look nice at lower ISO settings, but the trade-off between resolution and photocell size really doesn't pay off as well as the hype would suggest, and as a camera it's handicapped by the usual phone camera problem; the lack of an optical zoom lens, a sluggish AF system that doesn't work well in low light, and inaccurate and unreliable exposure metering.

Most mobile phone cameras use extremely small sensors, usually 1/3.2in, or in real terms approximately 4.54 x 3.42mm, with a surface area of 15.5mm2. Most compact cameras use 1/2.3in sensors, which typically measure 6.17 x 4.55mm giving a surface area of 28.5mm2. Advanced compacts such as the Canon G12 use a 1/1.7in sensor measuring 7.44 x 5.58mm, an area of 43.4mm2. The Nokia 808 PureView uses an even larger sensor than that; it's a 1/1.2in chip measuring 10.67 x 8.00mm, with a surface area of 85.33mm2. In other words, its sensor has nearly double the surface area of an advanced compact, and over five times the surface area of a typical phone camera sensor. However it's still only about a quarter the size of an APS-C sensor (typically 370mm2), and less than one-seventeenth the size of the 40-megapixel sensor (44 x 33mm, 1452mm2) in the Pentax 645D, the only camera with a comparable resolution.

What this means of course is that the individual photocells are extremely small, in fact they're 1.4 microns, roughly the same pixel density as a compact camera with a 13-megapixel 1/2.3in sensor. In fact, if you think of the sensor as three 13-megapixel 1/2.3in sensors bolted together it makes a lot more sense. Unfortunately, such overpowered compacts are very prone to excessive image noise. Photocells that small are relatively poor at capturing light, especially when there's not a lot of light around to be captured, so they tend to produce very poor image quality in low light situations. To try and get around this the 808 camera combines the output of several photocells into one pixel, a technology which Nokia calls "Pixel Oversampling", but which regular readers will recognise as "pixel binning", a common high-ISO noise reduction technique used in cheaper compact cameras. From its 41MP sensor, it produces images of 8MP, 5MP or 3MP, depending on the quality setting, combining the output of different numbers of photocells into one pixel in the final image. But then the 808 can also produce full-resolution images of 38 megapixels in 4:3 aspect ratio, or 36MP in 16:9, which is quite a party trick, and we'll be taking a look at these later.

Another technological breakthrough that makes this larger sensor design possible is the 808's high quality Carl Zeiss lens, which was specially developed to match the sensor. Usually a larger sensor requires a greater distance between the lens and the sensor, which is why more advanced cameras are usually quite big. By using a non-zoom, fixed aperture lens designed specifically to match this sensor, the camera unit on the 808 is able to remain relatively small, although it does still make quite a bulge on the back of the phone. The lack of optical zoom is something of a limitation, but the 808 does offer a "lossless" digital zoom, adjusting the pixel oversampling to compensate for the cropping of the image and retaining much the same quality.In terms of image quality, it's a mixed bag too. Some people have been raving about it, but to be honest I wasn't all that impressed. One of the main claims is that it's supposedly noise-free, but this is simply not true. Sure, at the 50 ISO minimum sensitivity setting the image quality is undeniably very good, but noise starts to appear even at 100 ISO, and by the 1600 ISO maximum setting it performs no better than any mid-price compact camera. The level of detail at the full-resolution 38-megapixel setting (or 32 megapixels in 16:9 format) is undeniably impressive, showing up tiny details in the scene amazingly well. In my usual sample shot it could easily pick out wood grain from thirty feet away, at least in good light.

However that's not really the way the camera is intended to be used. It's at its best in the 8-megapixel PureView mode, using the pixel oversampling technology to its best effect. In this mode the colour rendition is very good, with bright vibrant hues in good light, and plenty of fine detail, but it's really still not any better than a good 8-10-megapixel compact camera. Like everything else in the known universe, the 808 can also shoot 1080p video, and it has to be said that the quality isn't bad, although again it bears the 'for a phone' caveat. It suffers from the usual CMOS sensor "Jello effect" if you pan too quickly, but it has that bright LED light for extra illumination, and the sound quality - mono only of course - is surprisingly good.

Price : £490

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