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Sony, sensors, smartphones and sensation

Tuesday, November 18, 2014 12:00 AM

A leaked document suggesting that Sony is developing an Active Colour Sub Sampling Sensor had techies going wild over the weekend, while Sony itself has just announced a new sensor with HDR and auto-focus technology. What did WTS Production Specialist Patrick van Weeren make of it all?

Yesterday’s announcement from Sony revealing a new IMX230 Exmor RS sensor might normally be expected to set the heart-rates of technology lovers racing.

But that story has barely raised an eyebrow in light of last week’s leaked details of Sony’s supposed new image sensor technology which, if it comes to fruition, could surpass the standard Bayer colour pattern technology.

The first leak of Sony’s rumoured innovation came via Chinese website cnbeta.com last Tuesday, when alleged spec sheets for the IMX189AEG and the IMX197HSK were revealed. The ‘news’ was quickly picked up by Vladimir Koifman’s blog Image Sensors World and rapidly became the hot technology topic – and more details over the weekend further stoked the fires.

As a cameraman, I always find it interesting to look at the developments in sensor technology – not least in the smartphone world, as R&D budgets seem to be larger in that market, no doubt because of the sheer size of the industry. And should the technology make its way into professional cameras, it wouldn’t be the first time that we (don’t) get features that were developed for the consumer market first.

RED and other competitors have been working on 6K cameras and sensors for a while now, so it is no surprise that Sony is investigating new sensors. It would actually be more interesting if they didn’t.

What did catch my eye looking at the documents for all these sensors – official and unofficial – is the new technology for Plane phase AF detection autofocus (IMX230 sensor) and, even more so, the Active Pixel Colour Sampling (IMX189AEG/IMX197HSK).

Sony IMX197HSK leaked spec sheet

One of the documents leaked on cnbeta.com about a possible Sony IMX197HSK sensor

Active Pixel Colour Sampling – A new sensor technology?

Personally I have always been amazed that the Foveon sensor technology was acquired by Sigma and not by any of the bigger manufacturers. As a cameraman that used to work with analogue film, it seems to me to be the only sensor set-up that ‘sounds’ right – that is, it reflects the way that colour film would be layered to capture the image.

Foveon X3 film mosaic

The Foveon X3 Sensor (Image: foveon.com)

Now it seems that Sony may have found a new way of approaching this patented set-up on a pixel-based level. According to the published schematics the Sony system is not three-layered like the Foveon, but utilises a single layer, with the colour sampling on each pixel being achieved by the use of a moving(!) colour filter, together with a timed recording. In this way, the colour sampling can reproduce a full-colour image.

Sony IMX189AEG sensor structure (leaked)

Schematics showing the possible IMX189AEG sensor structure (Source: sonyalpharumors.com)

Having a system that uses one pixel for three colours compared to e.g. the common Bayer pattern sensors means that the number of pixels needed on the sensor can be dramatically reduced. Consequently the pixels themselves can be bigger, hence less noise, aliasing and moiré. If the rumours are true, the new sensor is also being read as an electronic global shutter. In short: fewer motion artefacts – all very positive specs.

The question is will a three-colours-per-pixel (Active Pixel Colour Sampling) approach bring its own artefacts? If this is just a way around the Foveon sensor patent, it might end up being too cumbersome. But if Sony does invent a new way of colour sampling it could be big news.

Remember, the Bayer pattern was invented by Bryce Bayer for Kodak in 1974! The sensor techniques that we use today don’t change as quickly as our video cameras do and that’s probably why this news has travelled throughout the tech world so rapidly.

Bayer pattern on sensor profile

Diagram explaining the Bayer Pattern sensor technology

Another interesting rumour surrounding this Sony sensor is the capability to boost slow-motion features to 16000 fps at 2K and 240fps in 4K. (Source: CnBeta.com)

Auto Focus System, 4K, HDR for the smartphone

After all that talk of potentially revolutionary new sensor technology, the IMX230 sensor, which is scheduled for release in April 2015, seems less exciting, because it still uses the Bayer pattern. The plane face detection auto focus with 192 AF points, on the other hand, is very interesting. If Sony expands its use of this technology into the top end of the industry, the future could be fascinating.

Another feature that’s worth mentioning is the HDR (high dynamic range) capacity of the IMX230, as shown below:

Sony IMX230 sensor HDR comparison

HDR has always intrigued me, especially when little gems of HDR images come to the market. This commercial, shot on a Canon 5D Mark II for Dutch bank ABN-AMRO, is a great example.

RED has incorporated a form of HDR (HDRx) into its technology. But the limitation of choice between shutter-speed HDR (movement issues) or ISO-based HDR (grain issues) has slowed the development of HDR for film use. Maybe these new sensor technologies will help the film-industry boost the dynamic range of their cameras even beyond 14 stops in moving pictures.

The last week has given us a glimpse into the future of sensor technology, mostly designed for smart phones – but possibly some of it might find its way into our cameras.

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