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The next step in sensor design for future cameras?


georg

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Nokia brought a new smartphone to the market with a fascinating camera:

 

http://i.nokia.com/blob/view/-/1486928/data/2/-/PureView-imaging-technology-whitepaper.pdf

 

People actually using it and you can google some impressive samples. Keep in mind: it's a smartphone camera without using backlit-CMOS, of course it's not a system camera.

 

The idea is to use a quite large sensor with very small photosites resulting in a very high pixel count. The quality-per-pixel is not very high (not too surprising) but the image is downsampled creating a "normal" megapixel-count but with excellent per-pixel-quality. Noise, lack of color artifacts and flexibility seem superior to conventional designs!?

IMHO, that would be an innovative approach for a future Leica camera, better than following the others with implementing a "me too" 50$-APS-C sensors in 2k++ cameras with a red dot...

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I read this as pseudo-technical advertising hype.

 

The smaller a pixel site is, the less light it can catch, and store. Hence, dynamic range suffers. Doing the same thing with a lot of adjacent sites does not change this – it can average out random shot noise, but not increase dynamic range.

 

Each f-stop equivalent of range means a doubling of the number of photons caught, and hence electrons stored waiting for the readout. The minimum is one photon/electron. Because of the noise threshold, which is the digital counterpart of film's 'base and fog density', you have to start the count higher. Oversampling can in theory decrease noise, but no matter where you start, where you are forced to stop because too many pixel sites are full and no more photons can be registered, will be crucial. And with submicroscopic pixels, you will have to stop very soon, unless Nokia or somebody has achieved a total breakthrough on the silicon level. Anyone that does that, will crow loudly about it. Heard any crowing lately?

 

And if that happened, if a totally superior level of performance was available at the silicon level, then that new revolutionary technology would instantly be available for larger sensors too, with mindblowing consequences. Don't hold your breath while you wait.

 

The old man from the P.T.Barnum Age

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I read this as pseudo-technical advertising hype.

 

The smaller a pixel site is, the less light it can catch, and store. Hence, dynamic range suffers. Doing the same thing with a lot of adjacent sites does not change this – it can average out random shot noise, but not increase dynamic range.

 

Each f-stop equivalent of range means a doubling of the number of photons caught [...]

 

Lars, the later sentence confuses me. Would not an additional f-stop require a squaring of the area?

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Lars, the later sentence confuses me. Would not an additional f-stop require a squaring of the area?

Doubling the area doubles the amount of light captured which in turn equates to one f-stop.

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"Hence, dynamic range suffers"

 

I think we can agree that Nokia just offered an interesting approach, not a replacement for high-quality cameras, just a glimpse into a possible future.

As you can combine several photosites for lower noise, you can combine them with different gains (or even ND-filters on top of a certain percentage of photosites) to increase DR as well. With a fill-rate close to 100% (so the light-sensitive area doesn't decrease with higher photosite count) on backlit-CMOS and powerful processors handling billions of pixels/second Leica could make a camera that has no AA-filter, can be used with different image size outputs based on the photographers needs (resolution, DR or high sensitivity) and make a camera (propably the EVIL we all hope for) that is ahead of competition and unique. Of course, that would mean to actually invest into R&D...

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A 3x3 pixel array with each pixel 2µm would have the same area than a 6µm pixel. If one would use the whole array (summing all 9 small pixels) and not a single pixel it should have the same DR as the larger. That assumes that the effective photo site of a 2µm pixel is 1/9 of a 6µm pixel. It might be possible to get RGB data from that single array (even only one micro lens per array). No Bayer or other pattern is necessary - more like Foveon with better DR?

It would increase resolution to the extend of a monochrome sensor and may improve color accuracy

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The EVFs are replacing the optical viewfinders. That implies necessarily new designs for CMOS sensors.

 

The next step will be full electronic shutter, this is, no mechanical shutter at all.

 

Several companies are working on it.

 

We are near I think...

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The next step will be full electronic shutter, this is, no mechanical shutter at all.

 

That would be very good for larger sensors, larger than 24x36, but there is not even a single CMOS for medium format

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  • 2 weeks later...

Why has the Foveon technology never been adopted by more manufacturers and developed any further? Looking at some sample images of the new DP2 Merrill I see the same crisp detail to that of the new M-Monochrome only that it is in colour.

 

Regards, Peter

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The same reason betamax never made it against VHS. It just never caught on. (betamax was the better system btw)

 

Everything was better than VHS at the time :) Interesting to see how often a lesser product benefits from good marketing. MS DOS & Windows are just another fine example - every other operating system was and still is better.

 

Regards, Peter

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