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Author Topic: Big Megapixel Camera in 2014  (Read 47844 times)

jrista

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Re: Big Megapixel Camera in 2014
« Reply #90 on: February 09, 2013, 04:46:03 PM »
@jirista: Thank you so much for taking your time to elaborate your explanation for me. Now I got a faint idea of what it is all about. I highly appreciate that! Has  there leaked any info (patents) that Canon are changing to the CP-ADC approach sometime soon? or let's say within the 5DIIIs or 6Ds body cycle? Could the rumored 5DX contain at least some first components towards this system? Looking forward to read about CP-ADC approaches related to future canon sensor designs....Cheers, Pedro

Glad I could help. :) I think the reason Exmor is so good is rather misunderstood...I even misunderstood it for a long time. Then I read a PDF article on it, and it all made sense. On-die parallel digital processing is really the way of the future, I think.

Regarding what Canon has, I really can't say. A lot of their patents are a bit over my head. I have a decent understanding of image sensor technology and electronics, so I can generally understand the bulk of their CIS patents, but when it comes right down to the exact mechanisms, I am not an expert, and I cannot say exactly 100% what Canon has up their sleeve. Also, I've only read the patents that have been granded and are publicly available...I'm sure Canon has patents they have filed over the last year or two that are pending grant, and not yet available to the public. What they may have pending could be anything...some form of CP-ADC is a possibility, CIS active thermal cooling is definitely another...but I have not seen explicit patents about them so far.

What I do know Canon has are regarding on-die hyperparallel readout logic. This does NOT include ADC, it is just column-wise parallel read. One of the readout patents described per-column  (rather than per-pixel) amplifiers, which I thought was interesting. Canon also has some interesting noise reduction patents. I don't understand them all (still need to finish reading and researching most of them). One that I did understand involved a power source disconnect feature in readout logic. The concept seemed to boil down to the idea that noise-generating dark current exists only when an active power source is flowing current through a circuit. Disconnecting the active power source, and using capacitance and existing charge to actually read out the pixel value, eliminated dark current as a source of noise.

The majority of the patents I have read seem to involve on-die readout logic. I am not sure that the stuff that occurs on-die (at least in Canon designs) is really the primary source of noise. Canon uses off-die ADCs housed in their DIGIC chips, across a high speed bus. I think the source of the most hated noise in Canon sensors...horizontal and vertical banding noise (HBVN, as I term it), is largely caused by the fact that read pixel data must then travel along a bus, after which they must be converted by high frequency ADCs. Assuming Canon has no on-die digital readout technology, I think their best option to reducing noise would be to eliminate that bus and move the ADCs on-die, in a much more parallel fashion than they have now. Even if it is not fully column-parallel, greatly increasing the parallelism beyond 16 and putting ADC on-die should help to reduce noise considerably.

There is also that ever-present die shrink. As pixel sizes get smaller, Canon is losing out in terms of Q.E. more and more. A 500nm process was quite good for APS-C and FF until a few years ago, however as pixel densities continue to increase, and as more and more logic is put on the same die as the pixels themselves, a 500nm process is going to really start hurting Canon's ability to compete on the sensor front. We've already seen it in the difference in IQ between the 5D III and D800, by an order of two magnitudes. A 180nm process is a three-fold shrink in transistor size. That means a few things. One, they can put more circuitry on-die without needing to dramatically increase the amount of power used (which, being the prime contributor to dark current noise, would have a negative impact on IQ).

Second, the usable area per pixel would increase at all sensor sizes and pixel densities. A 500nm transistor consumes a lot of space, which reduces the total photo-diode area that can actually receive photons. Microlensing helps, but it is far from perfect, and stronger, more precise microlenses are required when larger readout wiring and transistors are used. A 180nm process would allow more photodiode area to be dedicated to "pixel", and less to "transistor and wiring". Combined with better microlens technology, and possibly even better color filtering technology¥, Canon could bring their Q.E. up to competitive levels (55-65%), which would intrinsically reduce the impact of read noise. Add in their active thermal cooling, and Canon may even be able to turn the tables on their competition, surpassing D800 IQ (even without digital readout technology).

That is a LOT of technology Canon would need to bring to bear in the next cycle. They may have it, but perfecting such technology and making it viable for mass production takes time. If they have only developed some of that technology in the last year or so, it may still be another year or two before it is all actually ready for mass commercial consumption. I think the gambit for Canon is to figure out a way to "go digital". Analog signal processing has its advantages, is an extremely well known and well understood concept, but clearly digital signal processing, in the context of CIS, is and has surpassed it. And as time goes on, hardware DSP will only get better, and I suspect more and more DSP logic will shift on-die. If Canon cannot figure out a way to patent their own on-die CIS DSP technology, they will never really catch up to their primary competition (Sony). I can't say about other competition from other CIS manufacturers...not sure if any of them are actually doing the kind of digital readout that Sony CP-ADC does.

¥ Someone posted a very interesting link to a Panasonic patent that describes a color splitting replacement for color filters, which would allow all of the light incident on the sensor to be utilized, simply by redirecting light of certain colors to pixels of the matching color...i.e. Blue, White-Red, and White+Red. Right now, around 35-40% of the light incident on any given pixel is used, with the rest being filtered out. With color splitting in place of color filtering, the light that is not "appropriate" for any given pixel is simply redirected to the neighboring pixels where it is appropriate. Per-pixel quantum efficiency could technically double, from around 30-40% to 60-80%, if such technology could be idealistically employed. Note, per-pixel Q.E. is usually different than whole-sensor Q.E...currently, several Nikon cameras have greater than 50% Q.E., with one over 60%. That is for the entire sensor. With color splitting technology, theoretically I think Q.E. could reach 90% or more at room temperature. Combine that with some active cooling technology to eliminate thermal sources of noise, and the IQ of a future-generation image sensor with color splitting could blow even the D800 away, especially in extremely low light situations. Imagine taking a photo of an Aurora at a native ISO 204800 with IQ as good as or better than ISO 51200 today.
« Last Edit: February 09, 2013, 04:50:59 PM by jrista »

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Re: Big Megapixel Camera in 2014
« Reply #90 on: February 09, 2013, 04:46:03 PM »

TheSuede

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Re: Big Megapixel Camera in 2014
« Reply #91 on: February 09, 2013, 05:36:01 PM »
Every camera applies CDS, or Correlated Double Sampling. The point of CDS is to determine the reset dark current noise present in the sensor, before an exposure is taken. The charge of each pixel is registered and saved, and when the actual exposure is read out, the registered reset charge is subtracted from the exposure charge. That, effectively, eliminates noise caused by dark current present in the sensor at reset time. That is a moderate mount of noise, and exists in all sensors. It is not, actually, the worst form of electronic (read) noise, so CDS only does a partial job of removing noise in hardware.
.../cut a bucketload of text/...

There are some very dubious statements blended in there.

1) the patents regarding the exmor PRINCIPLE are highly questionable, and Sony knows this very well. Due to publicly available prior art, the general patents would never stand in court. This is why companies as Panasonic, Aptina and most notably maybe Cmosis in the latest Leica CMOS sensor use on-chip layouts very similar to the original "Exmor" patents. I doubt there's much difference between the Cmosis Leica M sensor and an exmor except in general detailing, the principles are all the same.

2) The more specified patents are in fact more of a copyright statement. "We implement this by doing this, and we do it in this way with this layout". That's normal behavior when you don't want others to copy your works by putting your stuff (basically) in a photocopier. It stops others from doing exact copies, it does not stop them from using the same basic flow principles.

In the end this means that the statement about "Sony having patended the way to get rid of banding and read noise" is pure BS. And when I say pure, I mean 100.00% pure.

That's kind of like saying that Ford has patented a car that does not swerve off the road and kill you every 50 miles or so. The general principle in itself (not killing you every 50 miles) is well known beforehand, and can be worked towards in many different and equally efficient ways.

There are thousands of possibilities for Canon's interleave readout to be balanced and banding-free. Literally thousands of ways to make it happen. Ten or fifteen of them would possibly be in conflict with a presently valid patent, but that should not stop them.

Regarding CDS, Canons version of CDS is actually more effective than the way Sony does it in some of their sensors (not all Exmor marked sensors have digital CDS!). This can be seen when you use the cameras at higher ISO - which is where the particular components of noise that CDS is meant to be working against is most visible.

Where Canon falls flat on their face is the path where the signal is taken FROM the sensor (after the CDS has already been applied) and VIA the ISO amplifier INTO the AD converters.
-That path is seriously unbalanced, and also quite noisy. In fact - at the lowest two full-step ISOs in a Canon camera, the sensor is nowhere near being the largest electronic noise-source. The stuff Canon use outside the sensor to digitize the signal adds four times more noise than the sensor does at base ISO.

jrista

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Re: Big Megapixel Camera in 2014
« Reply #92 on: February 09, 2013, 06:27:51 PM »
Every camera applies CDS, or Correlated Double Sampling. The point of CDS is to determine the reset dark current noise present in the sensor, before an exposure is taken. The charge of each pixel is registered and saved, and when the actual exposure is read out, the registered reset charge is subtracted from the exposure charge. That, effectively, eliminates noise caused by dark current present in the sensor at reset time. That is a moderate mount of noise, and exists in all sensors. It is not, actually, the worst form of electronic (read) noise, so CDS only does a partial job of removing noise in hardware.
.../cut a bucketload of text/...

There are some very dubious statements blended in there.

1) the patents regarding the exmor PRINCIPLE are highly questionable, and Sony knows this very well. Due to publicly available prior art, the general patents would never stand in court. This is why companies as Panasonic, Aptina and most notably maybe Cmosis in the latest Leica CMOS sensor use on-chip layouts very similar to the original "Exmor" patents. I doubt there's much difference between the Cmosis Leica M sensor and an exmor except in general detailing, the principles are all the same.

2) The more specified patents are in fact more of a copyright statement. "We implement this by doing this, and we do it in this way with this layout". That's normal behavior when you don't want others to copy your works by putting your stuff (basically) in a photocopier. It stops others from doing exact copies, it does not stop them from using the same basic flow principles.

In the end this means that the statement about "Sony having patended the way to get rid of banding and read noise" is pure BS. And when I say pure, I mean 100.00% pure.

Sony has patented their approach to CP-ADC, and the patents involve Digital CDS as part of the same curcuitry as the column-wise ADCs. It is a fairly specific patent. I am not sure there are thousands of ways of doing what Sony does, which is extremely effective, and that was what I was addressing.

There are thousands of possibilities for Canon's interleave readout to be balanced and banding-free. Literally thousands of ways to make it happen. Ten or fifteen of them would possibly be in conflict with a presently valid patent, but that should not stop them.

I'm sure there are thousands of ways of reducing noise in general. I would dispute the notion that there are "literally thousands of ways to balance interleaved readout and make it banding-free". Even the D5200, which uses a form of highly parallel, but not specifically column-parallel, readout has banding issues. Granted, they are a lot less than canons, but also plenty visible enough for people to complain about. To be 100% completely banding free, I do NOT believe there are unlimited options. Could Canon do it in a purely analog fashion? Maybe. Would it be as good as Sony Exmor? Possibly, but I'd call it s tall mountain to climb. Could they get as good as the D5200? Certainly.

Regarding CDS, Canons version of CDS is actually more effective than the way Sony does it in some of their sensors (not all Exmor marked sensors have digital CDS!). This can be seen when you use the cameras at higher ISO - which is where the particular components of noise that CDS is meant to be working against is most visible.

Regarding the fact that not all Exmor have DCDS, sure, there are a couple variants, one is BSI and designed for much smaller form factors, and its design is (probably by necessity) simpler than the FF version of Exmor. If you want to be that nit-picky, I'm explicitly referring to the FF and APS-C Exmor design as used in the D800 and D3200, both of which, as far as I know, employ CP-ADC with DCDS. As for Canons CDS working better than Sonys at higher ISO, I have no information to confirm or dispute that. Either way, though, read noise at higher ISO levels is such a minuscule factor of noise overall, which is completely dominated by Photon noise, I am not sure that Canon having a better CDS design even matters. Dark current's contribution to noise at that level is on the order of 2-3 electrons per pixel...trivial.

Where Canon falls flat on their face is the path where the signal is taken FROM the sensor (after the CDS has already been applied) and VIA the ISO amplifier INTO the AD converters.
-That path is seriously unbalanced, and also quite noisy. In fact - at the lowest two full-step ISOs in a Canon camera, the sensor is nowhere near being the largest electronic noise-source. The stuff Canon use outside the sensor to digitize the signal adds four times more noise than the sensor does at base ISO.

I don't dispute that. If you read my entire post, you would see I not only agree, I described that problem in detail. I am not sure that the off-die stuff adds 4x more noise than the sensor does (a reference where that is explained would be nice), but it is certainly the primary contributor. Canon's noise problem is primarily off the sensor die. Hence the reason I claimed (and have claimed for a while now) that Canon at the very least, even if they do not move to a digital readout and NR system, needs to get everything on-die. Shipping digital information along a bus for further processing is a hell of a lot safer from further contamination by noise than shipping analog information along a bus.

That is also the one area where Canon seems to be lacking patents. I have not seen anything that I could call an on-die ADC patent. I do believe that so long as Canon ships a huge amount of analog signal information off the sensor, especially if they use very few higher frequency off-die ADCs, they will always have high low-ISO read noise.

Don Haines

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Re: Big Megapixel Camera in 2014
« Reply #93 on: February 09, 2013, 07:42:22 PM »
I figure a BIG megapixel camera will need a big sensor..... Could this be what Canon has in store for us..... and just imagine the size of a telephoto lens!

http://www.dpreview.com/news/2010/8/31/canonlargestsensor
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jrista

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Re: Big Megapixel Camera in 2014
« Reply #94 on: February 09, 2013, 08:56:57 PM »
Jrista
i  do  not think you have the answer   what the_suede  is writing to  you.
Or what do you think  by your self ?

Sony has a  patented regarding  regarding  the count-down/count-up method of digital CDS. I have the patent
number somewhere, but I'm afraid not to hand right now. That mechanism is clever, but I wouldn't say
essential to operating digital CDS subtraction. For instance, the reset sample could simply be saved
in a register and subtracted with a simple adder - or both samples could be read and subtracted in
software. There are lots of ways round it, and it's not entirely clear to me that it is
qualitatively better than analog subtraction.


Yup, the ADU count-down/count-up is Sony's approach, but it is tightly integrated into their column-parallel ADCs. Instead of handling digital CDS off-die, for example, Sony simply integrates it directly into the ADC for each column. Reset count is negative, exposure count is positive, with the offset correcting the noise contribution from dark current present at sensor reset time. Concurrently, the specific approach to CP-ADC Sony uses cancels out banding via fine tuning each ADC (or maybe it is simply because they have an ADC per column, and the benefit is by default, as I have yet to find any patent directly describing how they cancel banding), which is how they correct banding. There is a nice PDF that explains it all...and I have the link...I'll go dig it up...



Here we go. Sony's CP-ADC paper. Seems there are two things that reduce banding. According to the paper, the use of analog CDS circuitry is itself the cause of some horizontal banding, due to variations in CDS circuits per pixel:

Quote
Also a capacitor with a size larger than a certain value is required in the CDS circuit to record and hold the post-CDS signal, and this results in an increase in the area of this circuit. Furthermore, the recorded and stored analog signals are easily influenced by switching noise in the high-frequency band due to the horizontal transfer operations.

To resolve these problems, Sony adopted the column-parallel A/D conversion technique. (See figure 2.) Since each column has its own A/D converter in the columnparallel A/D conversion technique, the analog signals read out from the vertical signal lines can be A/D converted directly.

Since the analog signals are A/D converted directly without first recording and storing, the capacitors that take up chip area as circuit structural components are no longer required. Also, the analog CDS circuits used for noise cancellation are no longer required. The CDS operation previously performed with analog signal processing is now performed with digital processing. This technique makes it possible to perform high precision noise cancellation that is not dependent on variations in the CDS circuits.

Additionally, Sony's CP-ADC, since it is low-frequency thanks to being per-column, allows them to eliminate high-frequency contributors to signal noise in the A/D conversion and Digial CDS unit (this is not really fine tuning each ADC, just that high frequency components that add noise are placed elsewhere, so vertical banding is not introduced in the first place):

Quote
Another advantage of the column-parallel A/D converter technique lies in its conversion speed. Since processing is performed in parallel for each column, the A/D conversion frequency is extremely low, and the high-frequency band noise components can be separated from the signal components.

For those who are interested in the exact process of A/D conversion and digital CDS in Sony's CP-ADC approach, here it is:

Quote
The column-parallel digital CDS technique operating sequence is as follows.
(See figure 5.)

  • Pixels are reset and the pixel reset state signal is output to the vertical signal lines.
  • PLL clock cycles are counted until the ramp wave matches the pixel output and a reset state signal A/D conversion is performed. Here the ripple counter is set to decrement count operation by the up/down switching signal.
  • Data signals are output from the pixels. At this point, the ripple counter is set to increment count operation by the up/down switching signal.
  • An A/D conversion of the same type as that of step 2 is performed and as a result the counter output indicates a value that is the value of subtracting the reset state signal from the data signal (digital CDS). Signals
    read out from the pixels are processed in a column-parallel manner.
  • The digital CDS operation terminates and the digital data is transferred to the latch circuit that is present in each counter block. This allows the A/D conversion of the next row and the horizontal data transfers to be performed in a pipelined manner.

So, I stand by my statements that Canon has an uphill battle to solve their banding problem and compete directly with Sony. It's been about 10 months since I last read that PDF, and I had thought there was additional fine tuning in the ADCs to eliminate banding. Well, for all intents and purposes, the simple fact that there is an ADC per column, and that all the high frequency components (like the clock and other logic control units, the D/A converter, etc.) are all elsewhere, away from the CP-ADC units, is why there is no vertical banding. The fact that digital CDS is performed by those same CP-ADC units, completely eliminating the need to handle CDS via analog circuitry, is the reason there is no horizontal banding. It is a very elegant and fairly simple solution to a problem that has plagued most sensor designs until recently (that includes very expensive medium format sensors). I can't say much about non-Sony competitors that achieve higher DR, although based on what I've read about the D5200, banding is not eliminated, just reduced thanks to a more parallel on-die readout approach.

If Canon wants to completely eliminate the most offensive kind of noise, horizontal and vertical banding, I think they have a tough job. I do not think there are a thousand ways of simplistically solving the problem as Sony did.
« Last Edit: February 09, 2013, 09:58:24 PM by jrista »

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Re: Big Megapixel Camera in 2014
« Reply #95 on: February 09, 2013, 09:45:16 PM »
I, for one, would happily spend a few grand on a high MP, high frame rate, 5D X (or whatever it ends up being called) if it had reduced read noise and competitive DR (i.e. at least 13 stops).
I'd do it even without the high frame rate, at least, higher than 5-6 fps.  I don't even care about high MP, I just want usable ISO 6400 / 12800, freedom from mirror slap, and an AF system that isn't an embarrassment:  the three biggest shortcomings of the 5D2.  Hell, I don't even care if it's APS-C instead of FF; I just want it to be useful for shooting my son.

As for APS-C going away -- not going to happen anytime soon.  Many Rebel buyers would rebel against the idea of a larger/heavier body that requires larger/heavier/more expensive glass.

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Re: Big Megapixel Camera in 2014
« Reply #96 on: February 09, 2013, 10:30:29 PM »
Yup, the ADU count-down/count-up is Sony's approach, but it is tightly integrated into their column-parallel ADCs. Instead of handling digital CDS off-die, for example, Sony simply integrates it directly into the ADC for each column. Reset count is negative, exposure count is positive, with the offset correcting the noise contribution from dark current present at sensor reset time. Concurrently, the specific approach to CP-ADC Sony uses cancels out banding via fine tuning each ADC (or maybe it is simply because they have an ADC per column, and the benefit is by default, as I have yet to find any patent directly describing how they cancel banding), which is how they correct banding. There is a nice PDF that explains it all...and I have the link...I'll go dig it up...



Here we go. Sony's CP-ADC paper. Seems there are two things that reduce banding. According to the paper, the use of analog CDS circuitry is itself the cause of some horizontal banding, due to variations in CDS circuits per pixel:

Quote
Also a capacitor with a size larger than a certain value is required in the CDS circuit...
(text cut, se previous post)

Additionally, Sony's CP-ADC, since it is low-frequency thanks to being per-column, allows them to eliminate high-frequency contributors to signal noise in the A/D conversion and Digial CDS unit:

Quote
Another advantage of the column-parallel A/D converter technique lies in its conversion speed. Since processing is performed in parallel for each column, the A/D conversion frequency is extremely low, and the high-frequency band noise components can be separated from the signal components.

For those who are interested in the exact process of A/D conversion and digital CDS in Sony's CP-ADC approach, here it is:

Quote
The column-parallel digital CDS technique operating sequence is as follows.
(text cut, se previous post)

The "low frequency" you're referring to is all due to the number of AD converters used. There's nothing advanced or even remotely "patentable" about this. The signal frequency in a readout is:
[# of pixels * ops per frame * fps] divided by [numbers of AD units used]
In a per-column system you get [the numbers of columns] AD-converters, in a normal ~20MP sensor that's about 6000. Many off-sensor AD systems use between 4-16 (Canon use 8-16, 5Dmk3 uses a 2x4channel setup and the 1Dx uses 4x4channels). That gives a (6048 / 2 / 8) = 400x lower quantization frequency if we assume that both are 14-bit and have the same fps. Quantization noise typically rises asymptotically with frequency above a certain point. Aptina have some systems with AD-on-chip that uses one for each 12 columns or some number close to that, giving about 400 AD converters per system. There are and cannot be any patents regarding how many AD converters per row or column you use.

To get rid of almost 100% of the banding effect, you just have to make sure that the response from each of the AD converters is the same as the others. Toshiba's effort in the 5200 sensor shows what you can achieve just by keeping a good control over your manufacturing process - since they don't use any kind of column-balancing strategy what so ever, except for the prerecorded dark frame on the Fujitsu made EXPEED chip - according to the die SEMs I've seen. So they show how well you can balance 6080 AD converters without any fancy processing, why can't Canon balance 8?

To increase the performance at lower ISOs, where the off-die electronics add in more noise than the on-die electronics in all Canon cameras - increase the quality of the off-chip electronics and fix the signal layout problems. This isn't very hard to do either - if you WANT to do it.

On-chip electronic noise is indeed very important at higher ISOs, just think about it. At ISO6400 you have ~64x less photons available than at base ISO, in a 5Dmk3 that makes about 1000e- per pixel give pure white. -4Ev, i.e slightly darker than middle gray is 16x lower than white: 1000/16 = 62 e-. The inherent noise in that gray is sqrt(62) = 8e-.

Now, compared to the 8e- of natural light noise, having 1e- or 10e- in added electronic noise makes quite a difference. Since Canon sensors have a very good on-chip CDS, they have a read noise of about 3e-. That's almost exactly the same as in the D800 sensor.

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Re: Big Megapixel Camera in 2014
« Reply #96 on: February 09, 2013, 10:30:29 PM »

jrista

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Re: Big Megapixel Camera in 2014
« Reply #97 on: February 10, 2013, 02:23:56 AM »
Yup, the ADU count-down/count-up is Sony's approach, but it is tightly integrated into their column-parallel ADCs. Instead of handling digital CDS off-die, for example, Sony simply integrates it directly into the ADC for each column. Reset count is negative, exposure count is positive, with the offset correcting the noise contribution from dark current present at sensor reset time. Concurrently, the specific approach to CP-ADC Sony uses cancels out banding via fine tuning each ADC (or maybe it is simply because they have an ADC per column, and the benefit is by default, as I have yet to find any patent directly describing how they cancel banding), which is how they correct banding. There is a nice PDF that explains it all...and I have the link...I'll go dig it up...



Here we go. Sony's CP-ADC paper. Seems there are two things that reduce banding. According to the paper, the use of analog CDS circuitry is itself the cause of some horizontal banding, due to variations in CDS circuits per pixel:

Quote
Also a capacitor with a size larger than a certain value is required in the CDS circuit...
(text cut, se previous post)

Additionally, Sony's CP-ADC, since it is low-frequency thanks to being per-column, allows them to eliminate high-frequency contributors to signal noise in the A/D conversion and Digial CDS unit:

Quote
Another advantage of the column-parallel A/D converter technique lies in its conversion speed. Since processing is performed in parallel for each column, the A/D conversion frequency is extremely low, and the high-frequency band noise components can be separated from the signal components.

For those who are interested in the exact process of A/D conversion and digital CDS in Sony's CP-ADC approach, here it is:

Quote
The column-parallel digital CDS technique operating sequence is as follows.
(text cut, se previous post)

The "low frequency" you're referring to is all due to the number of AD converters used. There's nothing advanced or even remotely "patentable" about this. The signal frequency in a readout is:
[# of pixels * ops per frame * fps] divided by [numbers of AD units used]
In a per-column system you get [the numbers of columns] AD-converters, in a normal ~20MP sensor that's about 6000. Many off-sensor AD systems use between 4-16 (Canon use 8-16, 5Dmk3 uses a 2x4channel setup and the 1Dx uses 4x4channels). That gives a (6048 / 2 / 8) = 400x lower quantization frequency if we assume that both are 14-bit and have the same fps. Quantization noise typically rises asymptotically with frequency above a certain point. Aptina have some systems with AD-on-chip that uses one for each 12 columns or some number close to that, giving about 400 AD converters per system. There are and cannot be any patents regarding how many AD converters per row or column you use.

I never said there was. The patents are for the design of the ADC/CDS units, not their frequency. The point is that *part* of that design involves keeping high-frequency components (i.e. the core PLL clock) out of the ADCs so they don't introduce high frequency banding.

To get rid of almost 100% of the banding effect, you just have to make sure that the response from each of the AD converters is the same as the others. Toshiba's effort in the 5200 sensor shows what you can achieve just by keeping a good control over your manufacturing process - since they don't use any kind of column-balancing strategy what so ever, except for the prerecorded dark frame on the Fujitsu made EXPEED chip - according to the die SEMs I've seen. So they show how well you can balance 6080 AD converters without any fancy processing, why can't Canon balance 8?

First, the Toshiba chip still has some banding, and its been enough to make customers complain. If we are talking 100% elimination here, so far, the only sensor I know that does that is Exmor.

According to the PDF, you don't need to actually balance anything. That is why I think it is rather elegant...according to Sony themselves, they eliminated circuitry, and moved circuitry around, to produce a low-noise environment for ADC. The simple nature of column-parallel ADC with digital CDS IS the solution to the problem. It is a very elegant, simple solution to the problem...that is what I love about it, and why I don't think it will be a breeze for Canon to reproduce. I thought there was some per-ADC fine tuning, but the sources of banding noise are the analog CDS circuitry itself (horizontal, thanks to transistor variance) and high frequency components in the ADCs (vertical, we all know about this). The very act of moving to CP-ADC (verses column-bucket parallel ADC like Toshiba) is what eliminates both forms of banding noise, effectively "for free".

To increase the performance at lower ISOs, where the off-die electronics add in more noise than the on-die electronics in all Canon cameras - increase the quality of the off-chip electronics and fix the signal layout problems. This isn't very hard to do either - if you WANT to do it.

I wouldn't call the quality of Canon DIGIC chips low. They are very high quality components already. They are also very high frequency components...high frequency, a major source of banding. Combine that with the use of analog CDS, which thanks to variance in the CDS transistors, causes horizontal banding, plus the high frequency bus to ship the analog sensor off the sensor die to those DIGIC chips...

Seems the trend of moving all of these components onto the sensor die and increasing parallelism is solving a lot of noise problems in and of itself. I don't think Canon is simply ignoring the problem...they aren't some evil corporation giggling gleefully as they watch their customers bleed cash. They have a transistor size problem, 500nm is showing its age. I think Canon can easily fix that, they have already demonstrated 180nm technology. I think now it is a matter of moving all that off-die junk onto the sensor die and increasing parallelism, and going digital. If they skip the digital part, I think things will definitely improve, but I doubt they will match Exmor in total quality.

On-chip electronic noise is indeed very important at higher ISOs, just think about it. At ISO6400 you have ~64x less photons available than at base ISO, in a 5Dmk3 that makes about 1000e- per pixel give pure white. -4Ev, i.e slightly darker than middle gray is 16x lower than white: 1000/16 = 62 e-. The inherent noise in that gray is sqrt(62) = 8e-.

Now, compared to the 8e- of natural light noise, having 1e- or 10e- in added electronic noise makes quite a difference. Since Canon sensors have a very good on-chip CDS, they have a read noise of about 3e-. That's almost exactly the same as in the D800 sensor.

Sure, the same as the D800 sensor at all ISO settings. I guess I don't see why the D800 having 2.6e- at ISO 6400 is a major contributor to noise when the 5D III has 2.9e-, and according to the review the 5D III seems to do better at high ISO settings than the D800. Noise at those ISO levels is so completely dominated by photon noise that the contribution from electronic noise is effectively meaningless.

Getting back on-topic. Canon has mentioned they have some new noise-reduction technology they have employed in the high-MP sensors floating around in prototype cameras. I don't know of any of that noise-reduction technology is on-die ADC and NR, but there was at least a rumor that they were using active thermal cooling which resulted in very low read noise. Sounds like that may take care of more dark current noise (which is usually what extreme cooling is employed for), however I don't know if that will address the issue of off-die ADC noise. I'm not sure a "little bit of balancing" will do much either...DIGIC is a high quality chip designed by Canon and manufactured at high quality fabs on modern processes. Canon may be able to reduce the 40mp sensor's contribution to read noise well below the 1e- mark with adequate active cooling, but will that take care of the worse offender....banding noise?

dilbert

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Re: Big Megapixel Camera in 2014
« Reply #98 on: February 10, 2013, 06:55:34 AM »
Quote
EOS 5D X?
A faster update? One suggestion from a known source is that Canon has loose plans to replace and/or update the EOS 5D Mark III quicker than the previous iterations. Could we see one some time in 2014? I would think a direct replacement would be unlikely, however a small, high performance & higher megapixel DSLR would probably have a place in the market.

I'm not surprised. The 5D Mark III has only delivered to a couple of segments of the 5D Mark II's market and the 6D delivers to only one (the amateur) and possibly none. The above rumor is undoubtedly in response to this plus the D800's lower price and the 5D Mark III "sales" that have been in the $2750-$2900 range indicating that Canon got the target price wrong, especially given two key feature comparisons (megapixels, IQ.)

There may also be questions being asked about the feature comparison with the 6D (WiFi, GPS)

In short, the only thing that Canon really got right with the 5D Mark III was autofocus (probably because that was the leading criticism from the 5D Mark II) but in fixing that, it is almost like they ignored the rest of the camera (sensor included.) Oops!

neuroanatomist

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Re: Big Megapixel Camera in 2014
« Reply #99 on: February 10, 2013, 07:12:09 AM »
In short, the only thing that Canon really got right with the 5D Mark III was autofocus (probably because that was the leading criticism from the 5D Mark II) but in fixing that, it is almost like they ignored the rest of the camera (sensor included.) Oops!

Yep.  The 50% faster frame rate, better sealing, better viewfinder, dual card slots, shutter lag reduced by half, better metering, better ergonomics including a multicontroller on the grip, etc., it does seem like Canon ignored everything but the AF.  Right.
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dilbert

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Re: Big Megapixel Camera in 2014
« Reply #100 on: February 10, 2013, 08:40:16 AM »
In short, the only thing that Canon really got right with the 5D Mark III was autofocus (probably because that was the leading criticism from the 5D Mark II) but in fixing that, it is almost like they ignored the rest of the camera (sensor included.) Oops!

Yep.  The 50% faster frame rate, better sealing, better viewfinder, dual card slots, shutter lag reduced by half, better metering, better ergonomics including a multicontroller on the grip, etc., it does seem like Canon ignored everything but the AF.  Right.

So Canon did all of this yet there are stories already about a quick replacement of the 5D3? Well, that tells you how important that list of "improvements" that you listed is, doesn't it?

If I want lots of frames per second then I buy a 1D series or 1DX series. If I want lots of fps, I don't buy the 5D3. Whilst the 5D3 may do more fps than the 5D2, you don't buy a 5D3 if you need high fps because if you do, the number of fps in a 5D3 is not going to be enough. And so on.

Let me put this another way. If I pick up and use a 5D Mark III, what am I going to notice as being significantly better aside from the AF? Nothing. What do I see as being better when I look at the images on my computer? Nothing.

So $800 or $900 more for improved AF.

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Re: Big Megapixel Camera in 2014
« Reply #101 on: February 10, 2013, 09:37:41 AM »
Yep.  The 50% faster frame rate, better sealing, better viewfinder, dual card slots, shutter lag reduced by half, better metering, better ergonomics including a multicontroller on the grip, etc., it does seem like Canon ignored everything but the AF.  Right.
And rate button! You forgot the rate button!

On a more serious note, it is funny how all of those things that you mentioned are of very little importance to me and most of my photography friends. :) I'll admit that the improved sealing is nice to have, but the rest of it is hardly a deal maker.

I'm not saying that the 5D3 is a bad camera, but it is still a very incremental upgrade from the 5D2. And compared to the advancements of the main competition, it just doesn't stand out. The 5D3 offers absolutely nothing to improve the IQ of my photos.

I welcome a quick replacement, or a 5D3X.
« Last Edit: February 10, 2013, 09:59:25 AM by Ricku »

neuroanatomist

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Re: Big Megapixel Camera in 2014
« Reply #102 on: February 10, 2013, 10:05:48 AM »
So Canon did all of this yet there are stories already about a quick replacement of the 5D3? Well, that tells you how important that list of "improvements" that you listed is, doesn't it?

It tells me nothing. There have been 'stories' of a new 100-400L for what...7-8 years?  There have even been at least two patents. Where's the lens? Stories.

As for a 5DIII 'replacement', I'd say BS and wishful thinking.  Many of the people clamoring for a high MP camera from Canon don't want to pay the price for a 1-series body, and from such dreams, rumors are born.

Let me put this another way. If I pick up and use a 5D Mark III, what am I going to notice as being significantly better aside from the AF? Nothing. What do I see as being better when I look at the images on my computer? Nothing.

So $800 or $900 more for improved AF.

Sorry, I completely disagree with that conclusion.  With a few notable (and *cough* vociferous) minority exceptions, the consensus was that the sensor-based IQ of the 5DII was excellent - it wasn't broke, and Canon didn't fix it.  Because of that excellent IQ, many people used the 5DII for tasks for which it's not ideal.  There's a reason I and a whole bunch of other people had both a 5DII and a 7D.  What Canon did with the 5DIII was, IMO, huge.  They took a camera with already excellent IQ, and improved substantially on the overall performance. 

For 5DII tripod-only, ISO 100 shooters, I can see the incremental nature of the upgrade. But if that's you, the answer is simple - keep your 5DII.

You state, "If I pick up and use a 5D Mark III...," which I take to mean you haven't.

After a couple years shooting a 7D and a 5DII, when I tried out a 5DIII what I immediately noticed was that it felt 'fast'. For example, the difference between the ~200 ms shutter lag of the 5DII and the ~100 ms lag of the 5DIII is very apparent.  My overall impression of the 5DIII is that using it feels like using a 7D from a performance standpoint, and it delivers the IQ of the 5DII - that's a powerful combination, and whereas the 5DII was liked (almost exclusively) for its IQ, the 5DIII is, IMO, the best all-around dSLR on the market.
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Re: Big Megapixel Camera in 2014
« Reply #102 on: February 10, 2013, 10:05:48 AM »

RS2021

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Re: Big Megapixel Camera in 2014
« Reply #103 on: February 10, 2013, 01:51:20 PM »

As for a 5DIII 'replacement', I'd say BS and wishful thinking.  Many of the people clamoring for a high MP camera from Canon don't want to pay the price for a 1-series body, and from such dreams, rumors are born.

+1
When I read the part about "quick" replacement for the 5D3, I laughed.  Then when I saw the peanut gallery rejoice that it will be so, I shook my head in disbelief... Sad in someways.
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LetTheRightLensIn

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Re: Big Megapixel Camera in 2014
« Reply #104 on: February 10, 2013, 05:07:20 PM »

As for a 5DIII 'replacement', I'd say BS and wishful thinking.  Many of the people clamoring for a high MP camera from Canon don't want to pay the price for a 1-series body, and from such dreams, rumors are born.

+1
When I read the part about "quick" replacement for the 5D3, I laughed.  Then when I saw the peanut gallery rejoice that it will be so, I shook my head in disbelief... Sad in someways.

If they do have some much better sensors coming out then I'd bet you the 5D3 will be replaced in less time than 5D2 to 5D3. If anything, I think it would be laughable to think otherwise (unless they also shift it a bit and give it a different name than the 5D4, but whatever it gets called no way it will take as long as 5D2 to 5D3 did or even 5D to 5D2 time). I'd be shocked if it doesn't arrive 2014 (two years vs 3.5 and 3 years).


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Re: Big Megapixel Camera in 2014
« Reply #104 on: February 10, 2013, 05:07:20 PM »