DxOMark Sensor Performance: Nikon vs. Canon
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tron said:
Well, Sony *might* produce a better sensor, but Exmor is already taking advantage of just about everything an 180nm process has to offer. If Canon moves to a 180nm process of their own, and starts using new tech like lightpipes and multi-layer microlenses and low-noise electronics, it could not only bring Canon up to Exmor quality, but it would level the playing field for the foreseeable future. The move to 180nm processes from 500nm is still relatively new, having only really first occurred a few years ago. It'll be some time before everyone moves to the next process shrink.
The next major innovation from Sony is to combine the image processing logic with the sensor die using a "3D" layered die attachment process. That won't really revolutionize IQ, but it will create much smaller, integrated packages for small sensors that can be used in phones and the like, making it even more cost effective to manufacture such devices.
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jrista said:
Maybe not revolutionize but will constitute the next major step in performance.
The big thing about the stacked/3D design is that the circuitry layer can be made ... cheaply ... on a state-of-the-art chipmaking process (say 45nm).
This will allow the integration of sophisticated on-sensor signal processing (per-pixel ADCs, dual conversion gain, etc.) - and in turn better overall sensor performance, which might prove impossible to match by a 'standard' sensor.
So, the stacked/3D design has a lot of promise, actually.
And unlike current BSI techologies, it will be much more cost-effective to scale to DSLR sensors.
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x-vision said:
Sorry, but I highly doubt stacked IC design will allow per-pixel ADC. Per-pixel ADC, just like any other per-pixel circuitry, would need to be PART OF THE PIXEL. That would have to be done on the sensor die, right on the photodiode. That would consume diode space, reducing FWC, which would have an impact on IQ. That is assuming an ADC could even FIT...they are much more complex than something like per-pixel CDS or a basic amplifier, which is a very simple thing in comparison.
I am not really sure what you would gain with per-pixel ADC over what Sony already achieved with per-column ADC anyway...Exmor's readout is about as clean as it is going to get without a more direct way of reducing dark current noise, which at this point is best done with very significant active cooling (i.e. peltier and a highly effective heat removal system, say copper heatsink and copper heat pipes, for freezing or sub-zero temperatures). Exmor already eliminated the downstream components that introduce noise, those being high frequency circuitry, such as a clock generator or PLL.
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PVS said:
Eyes roll....wow a guy with a video camera, web access and a pair of DSLR's....claiming to make an informed review.
Ok...here we go...he compares a 5DIII size against a D600....where the 5DIII has the optional grip...hullo?
Then makes a further eyes roll statement....the Nikon has dual SD card slots...which Canon doesn't have...when ever has an SD card been a cool thing compared to Compact Flash???
The Nikon has a pop up flash.....OH COME ON.....5 mins of my life wasted on this muppet.....
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ankorwatt said:
I've read the papers. The layers are not linked directly to the pixels. The sensor layer still has the readout circuitry, which then pipes that information to an image processor via a bus...it is just that the bus is directly integrated into the package, rather than being off the die and requiring transfer across significantly greater distances to some other off-die processor. I've seen no patents or papers that describe directly linking pixels to the packaged processing layer.
ankorwatt said:
In a sensor that introduces no downstream noise, such as Exmor, the primary source of noise is dark current. A heat sink is a PASSIVE cooling device. I am talking about an ACTIVE cooling device...such as a small peltier. Even though Exmor introduces practically zero downstream noise (the ADC introduces practically none as all the high frequency components are located away from the CP-ADC circuitry), it still has about 3e- read noise. That noise contribution comes from dark current in the sensor itself, and is the remnant that CDS is not correcting for. The only way to eliminate that is to cool the sensor. CMOS efficiency seems to reach its peak at about -80°C, at which point noise from dark current is ~200x LOWER than at room temperature. Cool the sensor, and the 13.23 stops of DR the D800 has would likely approach the theoretical maximum...say 13.999 stops of DR. That is another 2/3rds of a stop, which is still significant enough to be useful. It may be most useful for astrophotographers, but I figure I could use 20 stops of DR at least for my landscape photography...I'd still happily take the extra 2/3rds of a stop that a supercooled sensor would give me. That would also make a higher bit depth that much more viable...a 16-bit ADC on a sensor with active cooling...I see no reason why you couldn't get 15.9 stops of DR.
I don't foresee a peltier being used in a consumer device any time soon...the power requirements are more in line with using a fuel cell than a battery. But, actively moving heat away from the sensor rather than just with a passive heatsink would still introduce efficiency gains, and reduce dark current noise that CDS cannot compensate for.
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ankorwatt said:
You are misunderstanding my argument. I know exactly why Canon has poor low ISO DR. I am not talking about low ISO, I'm talking about high ISO. High ISO is greatly benefited by a high full well capacity and high quantum efficiency. Full well capacity is affected by two key things: total photodiode area and dark current leakage. The former can only be achieved with either a process shrink (this allowing all the circuitry for logic and readout to consume less diode space) or larger pixels. The latter is affected by temperature. Dark current leakage increases exponentially with temperature. Just lowering a sensor from 70°c to 50°c can cause a fairly significant improvement in quantum efficiency.
The efficiency of a photodiode to convert incident photons into free electrons (charge) can be critical to improving high ISO SNR. High ISO images are noisy not because the ISO setting itself introduces noise, but simply because a signal with a lower SNR is being amplified, and the noise already present in the signal is being amplified. We throw away the vast majority of light that passes through the lens, and only keep a small percentage...less than 20% in all consumer and professional grade cameras today. Of the light that passes through the lens and actually reaches the sensor, only about 30-40% makes it through the CFA, and with the average Q.E. of a CIS being around 40-50%, we throw away at least half of that! Even small increases in quantum efficiency can improve the signal level at HIGHER ISO settings. Ironically, a very high Q.E. might be counter-intuitive for low ISO settings as it could allow the sensor to saturate too fast, so one might need variable cooling in a sensor designed for optimal high and low ISO performance. The point is, however, that cooling the sensor to improve its efficiency (i.e. reduce dark current leakage caused by thermal factors) is all about improving the maximum potential signal at higher ISO settings.
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jrista said:
I think we've pretty well established that there are some people (e.g., Mikael/ankorwatt) and organizations (e.g., DxO) who believe that DR at ISO 100 is the only thing that's relevant. In my case, it might even be relevant....for the 17% of my shots that are at ISO 100. :
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neuroanatomist said:jrista said:
I think we've pretty well established that there are some people (e.g., Mikael/ankorwatt) and organizations (e.g., DxO) who believe that DR at ISO 100 is the only thing that's relevant. In my case, it might even be relevant....for the 17% of my shots that are at ISO 100. :
I doubt it. You can digitally push 5DIII ISO 100 RAW files a half dozen stops and still get clean images with just a very modest amount of NR. I'm sure the 1DX fares even better.
You don't strike me as the type to accidentally underexpose your shots by a half dozen stops, or who wants to turn completely blocked below-Zone-I shadows into highlights....
Cheers,
b&
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neuroanatomist said:jrista said:
I think we've pretty well established that there are some people (e.g., Mikael/ankorwatt) and organizations (e.g., DxO) who believe that DR at ISO 100 is the only thing that's relevant. In my case, it might even be relevant....for the 17% of my shots that are at ISO 100. :
*Sigh* I don't really know why I continue to argue the point. I know its pointless...
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The worshipers of "DxO scores are everything, low ISO performance of Nikon/Sony sensors are everything" are continuing to sing their sad old songs of worship & praise ... Hallelujah 
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An Intelligent Nikon Missionary,
May be an oxymoron,
But when missionaries start their trolling,
There's less Oxy and more Moron.
May be an oxymoron,
But when missionaries start their trolling,
There's less Oxy and more Moron.
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jrista said:
If I know something is pointless I tend not to bother. But I have noticed that some people never know when to give up. Me, I'm just going to go on taking pictures that really please me with excellent quality that surpassed my expectations by quite a long way. If someone wants to tell me how rubbish my photos are without ever seeing them, well I'm not going to be very impressed with their reasoning or judgement. ;D
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ankorwatt said:
Can a D800 recover an eight-stop-underexposed image as well as a 1DX can recover a six-stop-underexposed image? Sure, but who gives a damn? Unless, of course, you can't properly expose an image to save your life....
Nikon: the camera for those who wouldn't know what to do with an exposure meter if it flew at them out of a pressure cooker.
http://www.canonrumors.com/forum/index.php?topic=10008.msg253382#msg253382
b&
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jrista said:
I've concluded that the only way to deal with this whole 5d mk2 vs D800 'debate' is to answer with a little 'nonsense' rhyme ;D
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