PureView lives again - Sony announces 48MP sensor

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Sony just announced a sensor that takes us all right back to the halcyon days of the Nokia 808 PureView and the Lumia 1020 - this has 48 Megapixels and allows for lossless digital zoom, especially in video mode. It's a component that will let mainstream Android (and possibly iOS) smartphones achieve Nokia PureView-like functionality over the next few years.

I say 'PureView-like' because the tech here isn't quite as sophisticated. A quad-Bayer filter sacrifices daytime precise detail for better low light performance, and the implementation of lossless zoom in both still and video mode will be down to the individual manufacturers using this in their phones in 2019.

In other words, the Nokia 808 and Lumia 1020 remain the PureView kings in terms of implementation, whatever their other limitations. And don't forget the recent Huawei P20 Pro, which also used a quad-Bayer sensor. It seems that Nokia's original vision of a high resolution sensor to provide more information for imaging software to chew on is coming full circle and that modern handsets might work on similar, if not identical, lines.

It's also worth noting that modern chipsets are so fast that they can double up, with oversampling or pixel binning from this Sony sensor and multiple exposure combination, producing computational images that are super-pure. In theory!

From the Sony press release:

Sony Corporation today announced the upcoming release of the IMX586 stacked CMOS image sensor for smartphone cameras. The new sensor features 48 effective megapixels, the industry’s highest pixel count. The new product achieved a world-first ultra-compact pixel size of 0.8 μm, making it possible to pack 48 effective megapixels onto a 1/2"-type (8.0mm diagonal) unit, thereby supporting enhanced imaging on smartphone cameras.

...The new sensor uses the Quad Bayer color filter array, where adjacent 2x2 pixels come in the same color, making high-sensitivity shooting possible. During low light shooting, the signals from the four adjacent pixels are added, raising the sensitivity to a level equivalent to that of 1.6 μm pixels (12 megapixels), resulting in bright, low noise images.
In addition to these advantages, original Sony exposure control technology and signal processing functionality are built into the image sensor, enabling real-time output and a superior dynamic range four times greater than conventional units. Even scenes with both bright and dark areas can be captured with minimal highlight blowout or loss of detail in shadows.

As I understand it then, Quad Bayer gives original intensity/level detail at the pixel level, but colour information is blocked in groups of four pixels. The jury's still out - maybe this will work out 'better' after all?

By adopting the Quad Bayer color filter array, where the adjacent 2x2 pixels come in the same color, the new sensor delivers both high sensitivity and high resolution. In low light situations, such as shooting at night, the signal from the four adjacent pixels are added, raising the sensitivity to a level equivalent to that of 1.6 μm pixels (12 effective megapixels), to capture bright, low-noise photos and videos. When shooting bright scenes such as daytime outdoors, the built-in, original signal processing function performs array conversion, making it possible to obtain high-definition 48 effective megapixel images in real time.

Pixel array of the new sensor
(Quad Bayer Array)
(conceptual diagram)
Quad Bayer compensation

Array conversion using original signal processing
(conceptual diagram)

With no one actually wanting 48MP images, it will be interesting to see what manufacturers decide to do - I'd have though that outputting 12MP 'purer' photos was vastly preferable to giant 48MP, 20MB images. But we'll see. And what will camera software coders do in terms of achieving PureView digital zoom, for stills and video? We just don't know. Hopefully they'll do something along the lines of what Nokia did in 2011, but maybe there are still patents in place blocking copycats?

Source / Credit: Sony