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Author Topic: Canon Dual-Scale Column-Parallel ADC Patent  (Read 6932 times)

jrista

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Canon Dual-Scale Column-Parallel ADC Patent
« on: December 11, 2013, 02:33:01 AM »
It's been a while since I last scanned through Image Sensors World blog. Around the beginning of August, as a matter of fact. Since that time, they noted that Canon filed for a "Dual Scale" CPADC patent:

http://image-sensors-world.blogspot.com.es/2013/08/canon-files-for-dual-range-column.html

If I understand the diagrams and the patent correctly, and I am no CMOS engineer, it sounds like Canon is maybe following ML's lead in using a dual gain (i.e. Dual ISO) approach to achieving higher dynamic range. Given how long it takes to produce technology viable enough for a patent, I suspect Canon had this idea long before ML...perhaps it was simply that ML got wind of this patent, and looked for a way to achieve the same thing with current Canon sensors...either way, interesting.

The more interesting thing to me than the dial gain, though, is the CP-ADC design. I've long said that Canon needs to modernize their sensor design, get rid of the noise generators (i.e. ADCs) in their DIGIC chips, and bring all that image processing onto the same die as the rest of the sensor. This is what Sony did (although they took it a step farther and converted to a digital readout/CDS approach, whereas as far as I can tell Canon's is still analog CDS and whatnot until it is actually converted to digital), and they achieved some significant DR benefits from the move.

Anyway, personally, I'm glad to hear Canon is investigating these options. CP-ADC is something I've wanted Canon to do for a long time, happy to see they might actually do it. God only knows if/when this technology may actually find it's way into their sensors...I only hope and pray it is soon. And dual-gain to boot...which has the potential to support FAR more than 14 stops of DR. With a 16-bit CP-ADC, we might even see a full 16 stops of DR (and who knows what might come after that...20-bit, 24-bit ADC? Can't imagine the file sizes though...46mp * 24bit...phew, 1.1Gb RAW (uncompressed) data size! Canon will need a DIGIC more than four times as fast as the current DIGIC chip...)
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Canon Dual-Scale Column-Parallel ADC Patent
« on: December 11, 2013, 02:33:01 AM »

CarlTN

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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #1 on: December 11, 2013, 03:12:04 AM »
Very interesting, but recently you had said that if Canon relies on dual ISO, that's only a bandaid, and might not yield enough of a DR increase, at least with the combined benefit of a lower noise floor.  Obviously you meant more akin to what ML did, rather than starting from quasi-scratch, as this link hints at.

It seems to me there will be a lot of lossless compression necessary for the large RAW files (and a lot of processing power).  Also though, does this not make it likely, that the 2014 1-series camera, assuming it's in the 40MP range, may not use the above process?  If so, it might just "only" have 14 bit RAW capability.  I too was hoping it was actually going to be 16 bit, whether it actually got much over 14 stops of "real" DR or not.  That would really be something, if Canon just suddenly introduced a camera that could actually do 16 stops.

Are you planning on buying the new camera, early on?

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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #2 on: December 11, 2013, 04:09:45 AM »
Very interesting, but recently you had said that if Canon relies on dual ISO, that's only a bandaid, and might not yield enough of a DR increase, at least with the combined benefit of a lower noise floor.  Obviously you meant more akin to what ML did, rather than starting from quasi-scratch, as this link hints at.

Using the existing downstream amplifier on half the pixels, which is what ML is doing, is a bandaid (and not ideal, as it costs you in resolution). What Canon has patented here is MUCH better...the way I would expect it to be done. Since they are reading the sensor with two different gain levels, I really don't see why there would be any reasonable limits on DR for the foreseeable future...ML is only limited to 14 stops because the ADC is 14-bit. Technically, the potential for very scalable DR is there in Canon's patent (assuming I've understood it correctly, that is.)

It seems to me there will be a lot of lossless compression necessary for the large RAW files (and a lot of processing power).  Also though, does this not make it likely, that the 2014 1-series camera, assuming it's in the 40MP range, may not use the above process?  If so, it might just "only" have 14 bit RAW capability.  I too was hoping it was actually going to be 16 bit, whether it actually got much over 14 stops of "real" DR or not.  That would really be something, if Canon just suddenly introduced a camera that could actually do 16 stops.

Are you planning on buying the new camera, early on?

Agreed, normally a RAW file will have lossless compression. Still, a gigabit of information is a lot...you can't compress the read stream, really...you have to process it all in order to compress the output file. So, while from a storage space standpoint it wouldn't be all that bad, from an image processing standpoint...you would need much faster processors.

Canon, or someone, mentioned around a year ago, maybe not quite that long, that Canon might push a bit depth increase with the Big MP camera. Who knows if that is the case, it was a CR1, but still, interesting nevertheless. I can't imagine anyone pushing bit depth until there is a definitive reason to do so. For all of DXO's claims about the Nikon D800 and D600 offering more than 14 stops of DR, they are talking about downscaled output images. The native DR of the hardware itself is still less than 14 stops...13.2 for the D800 IIRC.

That's with 3e- of read noise...which is INSANELY LOW (usually, you don't see that kind of read noise until you start peltier cooling sensors to sub-freezing temperatures). There are a few new ideas floating about regarding how to reduce read noise. There have been a number of patents and other things floating around lately about "black silicon", a structural modification of silicon that gives it an extremely low reflectivity index, which supports a natural read noise level of around 2e- and some of the best low light sensitivity known, and it is being researched for use in extreme low light security cameras that can see by starlight (which blows my mind.) Theoretically, this can greatly improve DR at what would be high ISO settings.

Canon's approach with dual scaling is potentially another way to get a lot more average dynamic range at low or high ISO out of a single read by using two separate signals with different gain and sampling (I guess) to effectively do a low ISO and high ISO read at the same time for each pixel, and blend the results together using on-die CP-ADC.

As for new cameras...all that is on hold until I can get my business started and start making some money again. I don't have any plans to purchase anything at the moment, outside of possibly a 5D III if the price is right. I certainly won't be buying a 1D MPM (megapixel monster) any time soon if it hits with a price over $5k. Besides, I like to wait and see how things settle first...I am still interested in the 7D II, and want to wait for both cameras to hit the street and demonstrate their real-world performance before I make a decision.
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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #3 on: December 12, 2013, 11:07:04 AM »
I keep wondering what is going to happen in the future with dual-pixel technology. They have the ability to read both sides of the pixel seperately, I wonder how much work it would be to set the two sides to different ISO values, read them both, and combine the values for greatly expanded DR.

This would obviously require more computing power than just reading the sensor would, but comments out of Canon about the greater computational needs of future cameras ties in with this... I am really curious to see what happens with the 7D2..... It should be dual-pixel and dual processor (Digic6 or even 6+????) so it will be able to do a lot more computing than a 70D. The next year or so could be interesting.
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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #4 on: December 12, 2013, 11:51:45 AM »
I keep wondering what is going to happen in the future with dual-pixel technology. They have the ability to read both sides of the pixel seperately, I wonder how much work it would be to set the two sides to different ISO values, read them both, and combine the values for greatly expanded DR.

This would obviously require more computing power than just reading the sensor would, but comments out of Canon about the greater computational needs of future cameras ties in with this... I am really curious to see what happens with the 7D2..... It should be dual-pixel and dual processor (Digic6 or even 6+????) so it will be able to do a lot more computing than a 70D. The next year or so could be interesting.

They wouldn't need to bother with the dual-pixel approach with this patent. They simply read "the pixel" (regardless of whether it is a single photodiode, or two/four binned, whatever) with two different gain levels (different ISO settings, done simultaneously on different signals). This patent offers a much better way to solve the problem without resorting to "hackish" approaches like what ML did, or like what you suggest with reading one half the pixel at one ISO and the other half at another ISO (which wouldn't be nearly as good, since each half pixel is only getting half the light, so the half-reads would already be at a disadvantage large enough to completely eliminate any gains you might make with the dual-read process in the first place.)

Even better than simply reading half pixels at different ISO settings, this patent reads each pixel twice simultanesously at different gain levels, while also bringing the ADC on-die and column-parallelizing them, allowing them to run at a lower frequency, thus reducing their potential to add downstream noise. With column-parallel ADC, they could do what Sony Exmor does...per-column read tuning to eliminate vertical banding. It also brings in the benefit of shipping image data off the sensor in an error-correctable digital form, eliminating the chance that the data picks up even further noise as it travels along a high frequency bus and through a high frequency DIGIC chip. This patent would single-handedly solve a LOT of Canon's noise problems.

The only real difference between Canon's Dual-Scale CP-ADC patent and Exmor's is that Exmor uses digital CDS and digital amplification (basically, it is an entirely digital pipeline)...I see no mention of Canon's patent referring to digital data processing on-die. There are theoretically pros and cons to both digital and analog readout, so only time will tell (assuming Canon actually IMPLEMENTS this design sometime soon) whether Canon's approach produces results that are as good as Exmor or not. Sometimes it is easier, and more accurate/precise, to apply certain kinds of processing and filtering on an analog signal rather than digital bits.
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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #5 on: December 12, 2013, 06:25:43 PM »
I keep wondering what is going to happen in the future with dual-pixel technology. They have the ability to read both sides of the pixel seperately, I wonder how much work it would be to set the two sides to different ISO values, read them both, and combine the values for greatly expanded DR.

This would obviously require more computing power than just reading the sensor would, but comments out of Canon about the greater computational needs of future cameras ties in with this... I am really curious to see what happens with the 7D2..... It should be dual-pixel and dual processor (Digic6 or even 6+????) so it will be able to do a lot more computing than a 70D. The next year or so could be interesting.

They wouldn't need to bother with the dual-pixel approach with this patent. They simply read "the pixel" (regardless of whether it is a single photodiode, or two/four binned, whatever) with two different gain levels (different ISO settings, done simultaneously on different signals). This patent offers a much better way to solve the problem without resorting to "hackish" approaches like what ML did, or like what you suggest with reading one half the pixel at one ISO and the other half at another ISO (which wouldn't be nearly as good, since each half pixel is only getting half the light, so the half-reads would already be at a disadvantage large enough to completely eliminate any gains you might make with the dual-read process in the first place.)

Even better than simply reading half pixels at different ISO settings, this patent reads each pixel twice simultanesously at different gain levels, while also bringing the ADC on-die and column-parallelizing them, allowing them to run at a lower frequency, thus reducing their potential to add downstream noise. With column-parallel ADC, they could do what Sony Exmor does...per-column read tuning to eliminate vertical banding. It also brings in the benefit of shipping image data off the sensor in an error-correctable digital form, eliminating the chance that the data picks up even further noise as it travels along a high frequency bus and through a high frequency DIGIC chip. This patent would single-handedly solve a LOT of Canon's noise problems.

The only real difference between Canon's Dual-Scale CP-ADC patent and Exmor's is that Exmor uses digital CDS and digital amplification (basically, it is an entirely digital pipeline)...I see no mention of Canon's patent referring to digital data processing on-die. There are theoretically pros and cons to both digital and analog readout, so only time will tell (assuming Canon actually IMPLEMENTS this design sometime soon) whether Canon's approach produces results that are as good as Exmor or not. Sometimes it is easier, and more accurate/precise, to apply certain kinds of processing and filtering on an analog signal rather than digital bits.

Good explanation! Now I understand.... Thanks!
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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #6 on: December 13, 2013, 08:12:39 PM »
Also, Canon has a prior Foveon-like patent, and now this patent.  While there is certainly a large (sometimes insurmountable) gap between patent and product, these patents belie the statements those who suggest Canon is failing to innovate in the area of sensor design (as do prototypes like the 120 MP APS-H sensor).
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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #6 on: December 13, 2013, 08:12:39 PM »

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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #7 on: December 14, 2013, 12:06:20 AM »
I keep wondering what is going to happen in the future with dual-pixel technology. They have the ability to read both sides of the pixel seperately, I wonder how much work it would be to set the two sides to different ISO values, read them both, and combine the values for greatly expanded DR.

This would obviously require more computing power than just reading the sensor would, but comments out of Canon about the greater computational needs of future cameras ties in with this... I am really curious to see what happens with the 7D2..... It should be dual-pixel and dual processor (Digic6 or even 6+????) so it will be able to do a lot more computing than a 70D. The next year or so could be interesting.

They wouldn't need to bother with the dual-pixel approach with this patent. They simply read "the pixel" (regardless of whether it is a single photodiode, or two/four binned, whatever) with two different gain levels (different ISO settings, done simultaneously on different signals). This patent offers a much better way to solve the problem without resorting to "hackish" approaches like what ML did, or like what you suggest with reading one half the pixel at one ISO and the other half at another ISO (which wouldn't be nearly as good, since each half pixel is only getting half the light, so the half-reads would already be at a disadvantage large enough to completely eliminate any gains you might make with the dual-read process in the first place.)

Even better than simply reading half pixels at different ISO settings, this patent reads each pixel twice simultanesously at different gain levels, while also bringing the ADC on-die and column-parallelizing them, allowing them to run at a lower frequency, thus reducing their potential to add downstream noise. With column-parallel ADC, they could do what Sony Exmor does...per-column read tuning to eliminate vertical banding. It also brings in the benefit of shipping image data off the sensor in an error-correctable digital form, eliminating the chance that the data picks up even further noise as it travels along a high frequency bus and through a high frequency DIGIC chip. This patent would single-handedly solve a LOT of Canon's noise problems.

The only real difference between Canon's Dual-Scale CP-ADC patent and Exmor's is that Exmor uses digital CDS and digital amplification (basically, it is an entirely digital pipeline)...I see no mention of Canon's patent referring to digital data processing on-die. There are theoretically pros and cons to both digital and analog readout, so only time will tell (assuming Canon actually IMPLEMENTS this design sometime soon) whether Canon's approach produces results that are as good as Exmor or not. Sometimes it is easier, and more accurate/precise, to apply certain kinds of processing and filtering on an analog signal rather than digital bits.

Good explanation! Now I understand.... Thanks!

:)

I just hope it finds its way into a Canon camera body soon. The patent was filed pretty recently, so I am pretty doubtful we would see it in the likes of say the Big MP camera, or even the 7D II. If Canon employs the technology, I suspect it would be in something like a next generation 1D X or maybe the 5D IV. Kind of a bummer, thinking that far out...but then again, we don't yet know what technology Canon HAS employed in either the 7D II or Big MP camera yet!
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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #8 on: December 14, 2013, 01:43:56 AM »
Digic 6 is coming, we would likely see such a new converter in conjunction with a new processor.  I'd also bet on dual pixel technology for most of the new cameras that come out. That technology has potential for producing mirrorless bodies that are very competitive with DSLR's.  Fewer moving components in a camera body means more reliability.  That flapping mirror is the cause of many issues in photography, but even so, it works and nothing has matched it yet.

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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #9 on: December 14, 2013, 01:47:16 AM »
Digic 6 is coming, we would likely see such a new converter in conjunction with a new processor.  I'd also bet on dual pixel technology for most of the new cameras that come out. That technology has potential for producing mirrorless bodies that are very competitive with DSLR's.  Fewer moving components in a camera body means more reliability.  That flapping mirror is the cause of many issues in photography, but even so, it works and nothing has matched it yet.

Yeah, I bet we see DPAF in all new Canon bodies as well. I wonder if/when they will start improving that (QPAF?) The thing I want to see from Canon is something REALLY compelling on the EVF front. I can't even consider mirrorless, even with its advantages, until there is one HELL of an EVF to accompany it. Outside of landscapes, I rely so heavily on the viewfinder for everything else (even astrophotography...you MUST have an OVF to find and frame sky objects).
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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #10 on: December 14, 2013, 07:00:05 AM »
Digic 6 is coming, we would likely see such a new converter in conjunction with a new processor.  I'd also bet on dual pixel technology for most of the new cameras that come out. That technology has potential for producing mirrorless bodies that are very competitive with DSLR's.  Fewer moving components in a camera body means more reliability.  That flapping mirror is the cause of many issues in photography, but even so, it works and nothing has matched it yet.

Yeah, I bet we see DPAF in all new Canon bodies as well. I wonder if/when they will start improving that (QPAF?) The thing I want to see from Canon is something REALLY compelling on the EVF front. I can't even consider mirrorless, even with its advantages, until there is one HELL of an EVF to accompany it. Outside of landscapes, I rely so heavily on the viewfinder for everything else (even astrophotography...you MUST have an OVF to find and frame sky objects).

digic6 has been out now for about half a year is a p/s.... Perhaps we get to see dual digic6 in the 7D2...

I agree about EVFs... They are the future, but not quite ready yet. There are a few nice ones starting to appear that are getting close, but they are not there yet.
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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #11 on: December 14, 2013, 03:33:17 PM »
Yeah I posted this some months ago. I could swear you even commented on it then  ;D  ;). But I think the thread got quickly turned into a mess by all those calling it a troll thread and more DRibble and all that sort of nonsense and perhaps everyone forgot the basis of that thread.

We can just hope it is ready for the next main bodies.

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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #12 on: December 14, 2013, 07:47:42 PM »
Yeah I posted this some months ago. I could swear you even commented on it then  ;D  ;). But I think the thread got quickly turned into a mess by all those calling it a troll thread and more DRibble and all that sort of nonsense and perhaps everyone forgot the basis of that thread.

We can just hope it is ready for the next main bodies.

It's entirely possible I DID see it...but I've had a lot going on since August, and am still trying to get a business going, so it isn't out of the question that I forgot. :P

The only thing, tickling the back of my brain, that I worry about is Canon's pension for announcing really KICK-ASS things that...just disappear. Like a 120 MEGApixel APS-H sensor that could rip out 9.5 frames a second. I mean, come on. I wanted that years ago...I only want it even MORE so now. Why the hell isn't it in the Canon EOS Whoop-ASS Ds X yet?!??!?!?!!?!?!?!!!!!!! ;P
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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #12 on: December 14, 2013, 07:47:42 PM »

jrista

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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #13 on: December 14, 2013, 07:50:02 PM »
Digic 6 is coming, we would likely see such a new converter in conjunction with a new processor.  I'd also bet on dual pixel technology for most of the new cameras that come out. That technology has potential for producing mirrorless bodies that are very competitive with DSLR's.  Fewer moving components in a camera body means more reliability.  That flapping mirror is the cause of many issues in photography, but even so, it works and nothing has matched it yet.

Yeah, I bet we see DPAF in all new Canon bodies as well. I wonder if/when they will start improving that (QPAF?) The thing I want to see from Canon is something REALLY compelling on the EVF front. I can't even consider mirrorless, even with its advantages, until there is one HELL of an EVF to accompany it. Outside of landscapes, I rely so heavily on the viewfinder for everything else (even astrophotography...you MUST have an OVF to find and frame sky objects).

digic6 has been out now for about half a year is a p/s.... Perhaps we get to see dual digic6 in the 7D2...

I agree about EVFs... They are the future, but not quite ready yet. There are a few nice ones starting to appear that are getting close, but they are not there yet.

If Canon does indeed move the ADC onto the sensor die, they would have to design a new DIGIC to pair it with, since the ADC currently lives inside the DIGIC chip up through DIGIC 6. So, if say the 7D II got this new DS/CP-ADC design...I would then expect it to have a DIGIC 7 paired with it. I would also expect that it would only need one DIGIC...the only reason the 7D, 1D IV and 1D X have had multiple DIGIC chips was to increase the number of ADC channels...with ADC on the sensor die, so long as the DIGIC 7's raw processing power was sufficient, you wouldn't even need two.
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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #14 on: December 15, 2013, 02:21:55 AM »
Very interesting, but recently you had said that if Canon relies on dual ISO, that's only a bandaid, and might not yield enough of a DR increase, at least with the combined benefit of a lower noise floor.  Obviously you meant more akin to what ML did, rather than starting from quasi-scratch, as this link hints at.

Using the existing downstream amplifier on half the pixels, which is what ML is doing, is a bandaid (and not ideal, as it costs you in resolution). What Canon has patented here is MUCH better...the way I would expect it to be done. Since they are reading the sensor with two different gain levels, I really don't see why there would be any reasonable limits on DR for the foreseeable future...ML is only limited to 14 stops because the ADC is 14-bit. Technically, the potential for very scalable DR is there in Canon's patent (assuming I've understood it correctly, that is.)

It seems to me there will be a lot of lossless compression necessary for the large RAW files (and a lot of processing power).  Also though, does this not make it likely, that the 2014 1-series camera, assuming it's in the 40MP range, may not use the above process?  If so, it might just "only" have 14 bit RAW capability.  I too was hoping it was actually going to be 16 bit, whether it actually got much over 14 stops of "real" DR or not.  That would really be something, if Canon just suddenly introduced a camera that could actually do 16 stops.

Are you planning on buying the new camera, early on?

Agreed, normally a RAW file will have lossless compression. Still, a gigabit of information is a lot...you can't compress the read stream, really...you have to process it all in order to compress the output file. So, while from a storage space standpoint it wouldn't be all that bad, from an image processing standpoint...you would need much faster processors.

Canon, or someone, mentioned around a year ago, maybe not quite that long, that Canon might push a bit depth increase with the Big MP camera. Who knows if that is the case, it was a CR1, but still, interesting nevertheless. I can't imagine anyone pushing bit depth until there is a definitive reason to do so. For all of DXO's claims about the Nikon D800 and D600 offering more than 14 stops of DR, they are talking about downscaled output images. The native DR of the hardware itself is still less than 14 stops...13.2 for the D800 IIRC.

That's with 3e- of read noise...which is INSANELY LOW (usually, you don't see that kind of read noise until you start peltier cooling sensors to sub-freezing temperatures). There are a few new ideas floating about regarding how to reduce read noise. There have been a number of patents and other things floating around lately about "black silicon", a structural modification of silicon that gives it an extremely low reflectivity index, which supports a natural read noise level of around 2e- and some of the best low light sensitivity known, and it is being researched for use in extreme low light security cameras that can see by starlight (which blows my mind.) Theoretically, this can greatly improve DR at what would be high ISO settings.

Canon's approach with dual scaling is potentially another way to get a lot more average dynamic range at low or high ISO out of a single read by using two separate signals with different gain and sampling (I guess) to effectively do a low ISO and high ISO read at the same time for each pixel, and blend the results together using on-die CP-ADC.

As for new cameras...all that is on hold until I can get my business started and start making some money again. I don't have any plans to purchase anything at the moment, outside of possibly a 5D III if the price is right. I certainly won't be buying a 1D MPM (megapixel monster) any time soon if it hits with a price over $5k. Besides, I like to wait and see how things settle first...I am still interested in the 7D II, and want to wait for both cameras to hit the street and demonstrate their real-world performance before I make a decision.

Very informative points, thank you.  And I think it was you who first mentioned "black silicon" on here earlier this year.  I recall trying to read more about it, probably a link you posted.  I think I read something on Wikipedia about it as well, for what little that is worth.

Thanks for pointing out that the compression would be useless during the read and processing stage.  I knew that but hadn't even considered it...I was just thinking of the large files being written to a storage media of some kind.  It almost seems like the high processing power is more achievable than the speed required to write and store the files, say while at 5 frames a second or more.  You would need large internal buffer capacity.  I suppose some kind of wireless technique could be used to write very large files quickly to an external computer, or watch phone or something...haha!  I guess it would all get designed to work, if the need for really large files came to the fore...or rather when it does.

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Re: Canon Dual-Scale Column-Parallel ADC Patent
« Reply #14 on: December 15, 2013, 02:21:55 AM »