Its very true that simply adding a 16-bit ADC might not have any real-world effect. ... If the same exact sensor is used with a 16 bit ADC, its doubtful you would get more than the same 11.5 stops of DR it gets now.Thank you, that is the point that I have been trying to make. If other components in the signal chain limit the maximum signal level and the noise floor anyways, increasing the ADC precision will only make for more precise measurements of noise.
Sure. There definitely has to be improvement in the whole pipeline to really make significant gains beyond 14-bits. There isn't going to be a magic bullet there...if just adding a 16-bit ADC was enough to instantly earn you a couple extra stops of DR, in this highly competitive environment it would have already been done. That's why I'm not surprised to hear rumors about 16-bit, active sensor cooling, new sensor designs, etc. Canon has a LOT of work ahead of them if they really want to start competing, and if the rumors are true, it sounds like they are serious about reclaiming...or at least attempting to reclaim...the technology crown.
I dont know if the observed noise in Canon cameras come from the image sensor, signal amplifier, the analog front-end of the ADC, the wiring or something else. I dont think it matters that much, either.
Well, I would bet its from multiple sources. Fixed-pattern noise is caused by the physical nature of the sensor itself...nanoscopic defects and the like. Pattern noise is caused by the readout mechanics and interference mechanisms, which also occurs on the sensor. "Read noise" is usually introduced by the ADC itself due to its high operating frequency. Read noise tends not to be significant, however the ADC converting (and potentially amplifying) the entire signal, and by the time the signal gets to the ADC, it already has FPN and Pattern noise in it, so read noise is ON TOP of those other forms of noise. The ADC is also responsible for quantization noise, which occurs when you have a non-integral conversion factor (i.e. 2.6 electrons convert into one digital unit...you can't convert 2.6 electrons...you either have to convert 2 or 3 electrons, so the ADC periodically swaps back and forth between converting 2 for a while then converting 3 for a while, introducing a very slight differential...quantization noise.)
Increasing the number of ADC's can help a little. Putting the ADC on the sensor die and hyperparallelizing it would probably offer significant gains. Each ADC could run at a lower frequency, reducing or eliminating additional read noise. You could tune each ADC to the column or row it operates on, reducing fixed pattern noise (at least in one direction...horizontal or column). Canon's correlated double-sampling patents are pretty old...I think they date back to the late 1990's/early 2000's. That helps eliminate dark current noise, but it could probably be improved to provide greater benefits, and reduce noise at the time of pixel read even more. There are probably a whole slough of other types of electronic noise introduced by circuitry around the photodiode or in the sensor in general that affect IQ. Advanced noise compensation circuitry could be added for any one of them or all of them to further reduce "electronic noise" before its amplified by the pixel or by any additional downstream amplification (which Canon sensors seem to have, which is why noise off the sensor itself is so bad...something downstream, either in the ADC or just before it, is amplifying it further.)
There is one tried and true way of reducing electronic noise though: extreme thermal cooling. At room temperature, 70°C or around there, electronic noise can be pretty high. Cool an electronic die down to -80°C, and you reduce electronic noise by 200x or so. Scientific-grade CCD's frequently do this, and the efficiency goes through the roof. Read noise is nearly eliminated. Quantum Efficiency skyrockets to over 80%, in some cases over 90%. If Canon is pursuing some form of active cooling, they very well could reduce their read noise below Sony Exmor levels. They will probably have to draw a fair bit more power than Exmor's approach (which uses circuitry rather than cooling to solve the problem), but the results could be pretty incredible.
On the flip side, if it works, Sony could just add active cooling to Exmor and leapfrog Canon again.