Sony 'boosts low-light picture quality' with white pixels

Sony RGBW test shots Sample pictures suggest that images taken with the new technology (right) display more detail

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Sony is promising improved low-light photography from its forthcoming range of smartphone camera sensors, thanks to the addition of white-light pixels.

The technology adds the white-light detectors to the red, green and blue (RGB)-sensing pixels already included in its existing devices.

Kodak patented a similar technology in 2007 but never put it to use. It is unclear whether Sony licensed the idea.

The move may help Sony sell more sensors to other manufacturers.

Smartphones typically use smaller lenses and image sensors than dedicated cameras, delivering blurred or dark pictures in low light.

Only a limited number have flashlight capability, which can be taxing on battery life and produce washed-out pictures.

After focusing on megapixels for years, camera sensor-makers are increasingly promoting low-light functionality as a selling point.

"This is good news for device makers, they can improve their cameras and give consumers a more functional camera that will work in better lighting situations," said Brian Blau, research director at the technology consultants Gartner.

"That really means consumers have to think less about how to process their pictures and just have fun taking them."

Dynamic range

Although white-light sensing pixels cannot distinguish colour, they have a higher sensitivity to light across the entire visible spectrum thanks in part to the fact they do not have a colour filter covering them.

Software is then used to combine this information with the detail recorded by the RGB pixels to provide a better shot.

"The reason why they are doing it is to capture more information about the shadow areas and to help it increase the dynamic range of the image, which in theory should help mobile phone sensors and very small compact camera sensors pick up more detail," said Richard Sibley, senior technical writer at Amateur Photographer magazine.

When Kodak patented the idea it noted that the technology would be suitable in situations involving "short exposure time, small aperture, or other restriction on light reaching the sensor".

It specifically mentioned "non-camera devices such as mobile phones and automotive vehicles" as two examples.

Sony's press release notes that introducing white-light sensing pixels would normally have the side-effect of "degrading" the picture.

But it adds: "Sony's own device technology and signal processing realises superior sensitivity without hurting image quality."

Sony aims to ship samples of the new sensor in March and says consumers may be able to buy devices using the technology later this year or early 2013.

Neither Sony nor Kodak responded to requests for more detail about the patents involved.

Organic sensors

Several camera makers are pursuing new ways of improving low-light performance.

The most common method is to use another technique pioneered by Sony: "back-lit" sensors.

The method involves shifting the circuit wiring that supports the pixels from the top of the sensor to its underside, allowing the pixels to be larger and so capture more light.

Sony's new "RGBW" sensors also use this feature.

However, Fujifilm is also working on an alternative technology involving a sensor with an "organic" layer which it says improves sensitivity, allowing the pixel sizes to be made smaller while capturing similar levels of detail. The firm was granted a US patent for the invention last year.

However, Fujifilm's innovation is thought to be destined for large mirrorless cameras with interchangeable lenses, rather than the smartphones Sony is targeting with its new hardware.

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