Monthly Archives: February 2012

Interessant gennemgang!

Interessant gennemgang!

Originally shared by Toke Eskildsen

1 pixel from Nokia 808 PureView is 8 pixels big. This is not as dumb as it sounds.

In the camera world, one observation for years has been more pixels = lower quality (although most stores try to equal more pixels with higher quality, thus aptly demonstrating that they are here to sell, not help the customer make the best choice. But I digress). For the non-techies: Many pixels normally means that each measuring point (normally 1 for each pixel) is very small. The smaller the measuring point, the lower the quality, especially when the light is not optimal.

The new Nokia PureView uses a 41MP sensor, which at first glance is pure insanity. With that high a pixel count in a phone, one would expect heavy noise due to the exceedingly small measuring points. However, the people at Nokia are trying something new.

First of all, the measuring points are not that small. The full sensor is 1/1.2″, which is near a low-end DSLR. According to Nokia, that is 5 times a normal phone camera sensor, which sounds believable. Sanity-checking, 41MP/5 ~= 8MP, so we have the noise-equivalent of a 8MP “standard size” sensor.

Second, they have fitted the phone with a large non-zoom lens, which has an aperture of f/2.4. This translates to high quality, lots of light to the sensor and the narrow depth of field associated with DSLR photos.

Third, and here’s the kicker: The phone does not make 41MP pictures. All the pixels are just a means to an end. Photos are 5MP, down sampled from 41MP. This would be the equivalent of measuring points 8 times that of a normal camera phone, if not for the problem with making very small measuring points. In reality it will be less than 8 times, but still markedly better than standard. Same goes for movies BTW.

So why not just make a big 5MP or 10MP sensor and get near-DSLR quality with a phone camera? Apparently Nokia likes zoom. With 41MP, zoming is a matter of selecting the desired rectangle and down sampling that instead of the whole area. Having fewer pixels to down sample means lower quality, but keeping in mind that the measuring points themselves are comparable to a generic phone camera, that is not too bad.

A winning formula, right? Well, at least two problems persists:

1) Although the glass in front of the sensor is relatively large and of high quality, 41MP is still an awfully high resolution to resolve optically. It is highly doubtful that the glass can deliver that. Still, even with reduced practical optical resolution, the overall principle should work okay.

2) More pixels still equals lower quality. Although the sensor rivals low-end DSLRs in size, all the pixels (and the space between them) means more noise. Nokia trades zoom-capability for quality, although the trade-off is somewhat offset by the “high quality at widest angle”, “standard quality at narrow angle”-scale. I am sure that the end result raises the bar for camera phones considerably, but had they opted for a large sensor/low pixel count approach, it would have been spectacular.

If the reviews confirm the theory and the camera finds its way into a decent Android phone, I see no reason to keep my pocket camera. I urge anyone interested to read the white paper at http://europe.nokia.com/PRODUCT_METADATA_0/Products/Phones/8000-series/808/Nokia808PureView_Whitepaper.pdf – it is a sober and easy read.

http://europe.nokia.com/find-products/devices/nokia-808-pureview/features#camera

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