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PostPosted: Thu Feb 18, 2010 12:29 am 
Here is an interesting article I finished reading.

http://www.eoshd.com/entry.php?29-Panas ... ure-sensor

A direct quote from the article:

Here are the key points:

* Panasonic have developed a 4K x 2K image sensor (approx. 12 megapixel) based on 'dual exposure technique'
* The sensor is described as having new architecture that tries to improve sensitivity by a factor of 4 or more
* The architecture change is a new design which allows green pixels to be read independently of the blue and red ones on the sensor.
* The green pixels are exposed 4 times longer than the red and blue, thus achieving the sensitivity gain
* Motion artifacts are introduced as a result, but clever signal processing of the red and blue channels corrects the motion artifacts introduced in the green channel by the long exposure
* Red and blue channel gain achieved by pixel binning in 4x4 mode


The technique is similar to the Intelligent Resolution feature of the new Panasonic TZ10 sensor, but on a larger scale.

A factor of 4 increase in sensitivity will allow the Micro 4/3rds camera to surpass the full frame Canon 5DMkII. GH2 is currently slated for a September release date - partly due to delays last year in Panasonic commissioning their new Japanese sensor fabrication plant in Tonami and strategical decisions related to the worldwide economy and consumer electronics market performance.


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PostPosted: Thu Feb 18, 2010 7:31 am 
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Thanks for sharing - interesting article, although I'm surprised to find official discussion of a future camera's specs by an employee...


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PostPosted: Thu Feb 18, 2010 10:59 am 
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Looking forward with even more than the usual relish to your GH2 review then, Gordon.

If true I wonder how this would work in practice: here's some speculation on my part. Assuming the full-well capacity of the various pixels remains unchanged then there's no advantage to applying this technique at low ISO numbers. At higher ISO numbers (higher read-out amplifier gain settings) it would seem that the amplifier gain for the green pixels is set lower than that of the blue and red pixels so allowing those longer exposures without clipping occurring at the analogue to digital conversion stage.

So at high ISOs we have a sharp-ish image from the blue and red channels which will suffer from noise and, depending on the degree of motion blur and camera shake, a fuzzier image from the green pixels. With a normal Bayer sensor layout there are twice as many green pixels as there are blue and red pixels so just using the red and blue channels gives you about half as many pixels to work with compared to the sensor's total pixel count. Thus combining the red and blue pixels to get a luminance signal from which to sharpen the whole image results in a best case drop in linear resolution to about 70% of the normal figure.

Then there's the issue of the colour signal. On the face of it chroma noise from the red and blue channels cannot be any better than from an equivalent normal sensor at the same ISO but at high ISOs we now have a much cleaner signal from the green channel. The article refers to pixel binning the red and blue pixels in 4x4 mode so we have a cleaner chroma signal from those channels but at the cost of a 50% reduction in linear resolution and a normal resolution chroma signal from the green pixels and, as a result of the pixel binning, all three colours have an equivalent level of noise. It would seem that the in-camera processing would have to make special provision to counter colour fringing at edges but such things have been done before. There's no such thing as a free lunch, however, and for sure there will be some images (feathers, maybe) which could catch the camera out.

But that said maybe this could be a useful advance for many situations where one is forced to work at high ISO numbers. It seems to rely on the fact that the human eye needs less colour linear resolution than luminance linear resolution, a fact that colour televisions based on NTSC and PAL have used for years. Yes, it will probably get caught out by some images and, if my guess above is correct, when working at full stretch there has to be a 70% loss in linear resolution when motion blur or camera shake are factors.

But hey, this is all speculation on my part and the acid test will be the reviews. But I think the reviewers will have to be on the lookout for the sort of potential issues I've described or they could miss them and give such sensors a better write-up than they might deserve.

Bob.

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PostPosted: Thu Feb 18, 2010 12:51 pm 
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I'm a little sceptical on the presented claims on this sensor. Particularly the reference to the 5D2. If you can do it to a little sensor, why not do it to a big sensor too? The performance gap will still fall back to the difference in sensor size.

So like Bob I'll wait for real world samples before you can call me a believer that it'll deliver the claims. Particularly on fast motion scenes...

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PostPosted: Thu Feb 18, 2010 11:58 pm 
Not sure if this is related at all:


http://www.evolve.com.my/


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PostPosted: Fri Feb 19, 2010 5:12 am 
Hi,
Very exciting post!
Just thinking, that if this 4/3" sensor can surpass a full frame one, then when this technology is applied on a full frame sensor, does is mean that the picture quality will be even better? If yes, this may be another revolution!
It seems now manufacturers are seriously thinking about image quality and noise and low light shooting. I guess earlier we were fooled by megapixels, but now it should be possible to get great image quality in even p&s cameras soon, maybe within a year!
Meanwhile, hoping the bsi cmos stands up to its claim....
Jinay.


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