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Author Topic: More Big Megapixel Talk [CR1]  (Read 85227 times)

jrista

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Re: More Big Megapixel Talk [CR1]
« Reply #165 on: October 03, 2012, 01:15:09 PM »
It's not they are not understood. Their derived data are just plain wrong sometimes while their RAW data is fine.

Explain :-[

Well, the obvious example is the DR score on a sensor like the Nikon D800 - DxOMark reports that as 14.4 EV, while the sensor has a 14-bit analog-to-digital converter meaning a real, measured DR of 14.4 is electronically impossible for the sensor.  If you look at the raw data they actually measure, before their flawed method of normalization, it's 13.2 EV (which is, of course, very good...just not impossibly good).

This is exactly correct.

@GeneralStuff: If you are truly concerned about what the "camera" can do, you want to look at DxO's "Screen DR" results. Screen DR is what the sensor/ACD/image processor in the camera itself produces in the RAW image. Print DR, on the other hand, is what computer software produces after some specialized processing well past the point its been imported off the camera, and has little to do with the actual hardware capabilities.

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Re: More Big Megapixel Talk [CR1]
« Reply #165 on: October 03, 2012, 01:15:09 PM »

generalstuff

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Re: More Big Megapixel Talk [CR1]
« Reply #166 on: October 03, 2012, 05:40:02 PM »
Sorry, then you do not understand the read outs from Nikon and the Sony sensors , and  it is more than one  data reading.
Even the D3x with 12 bit ADC have more than 12 stops DR because of more than one data reading
Study the subject before pre mature conclusions

Razor2012

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Re: More Big Megapixel Talk [CR1]
« Reply #167 on: October 03, 2012, 06:28:32 PM »
Guys, no matter what facts you have or what you say it's not going to help much, lol.
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neuroanatomist

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Re: More Big Megapixel Talk [CR1]
« Reply #168 on: October 03, 2012, 07:25:48 PM »
Guys, no matter what facts you have or what you say it's not going to help much, lol.
I know, I know.  But...the windmill is right there, just sticking straight up out of the field and begging to be tilted at and charged...

Sorry, then you do not understand the read outs from Nikon and the Sony sensors , and  it is more than one  data reading.
Even the D3x with 12 bit ADC have more than 12 stops DR because of more than one data reading
Study the subject before pre mature conclusions
Really, the D3x has a 12-bit ADC?  Quick, you'd better call Nobuyoshi Gokyu (President & CEO of Nikon, Inc., but I'm sure you know that) and tell him that the features page for the D3x, which states, "Fast 14-bit A/D conversion incorporated onto the image sensor," is wrong and needs to be corrected immediately, based on your thorough understanding of the read out from Nikon sensors.

So, if we can agree that Nikon is correct about their own D3x specifications, and that you, despite your extensive understanding and studying, are wrong about their D3x specifications, let's just say that the D3x has a 14-bit ADC and move on...

In that case, DxO's measurements show a very decent 12.84 EV of DR for the D3x.  Their 'Landscape Score', however, is an artifically inflated 13.65 EV - still technically possible (unlike the D800), but again, artifically inflated as a direct result of a flawed method of data analysis.

Study the subject, indeed.  Oh, puuullllleeeeeeeze.  It's almost as if I didn't have a day job that includes both analyzing quantitative image analysis data and managing a large group of scientists who do the same...  ::)
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jrista

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Re: More Big Megapixel Talk [CR1]
« Reply #169 on: October 03, 2012, 07:39:44 PM »
...

Study the subject, indeed.  Oh, puuullllleeeeeeeze.  It's almost as if I didn't have a day job that includes both analyzing quantitative image analysis data and managing a large group of scientists who do the same...  ::)

 ;D *clap* *clap* *clap* *clap* ;D

elflord

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Re: More Big Megapixel Talk [CR1]
« Reply #170 on: October 03, 2012, 09:10:11 PM »
This is exactly correct.

@GeneralStuff: If you are truly concerned about what the "camera" can do, you want to look at DxO's "Screen DR" results. Screen DR is what the sensor/ACD/image processor in the camera itself produces in the RAW image. Print DR, on the other hand, is what computer software produces after some specialized processing well past the point its been imported off the camera, and has little to do with the actual hardware capabilities.

 "The hardware" does not consist of a single pixel. "Screen" is fine if you want to evaluate the capabilities of a single pixel.

If the cameras being compared have similar resolution, the difference should be relatively minor.  (EDIT I mean both cameras should see their "dynamic range" change by a similar margin, which is the case with the D800 vs 5DIII for example -- depending on whether you believe the "screen" or "print" number, the Nikon wins by 2.5 stops, or "only" 2.2 stops.)
« Last Edit: October 03, 2012, 11:09:30 PM by elflord »

elflord

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Re: More Big Megapixel Talk [CR1]
« Reply #171 on: October 03, 2012, 09:13:15 PM »
It's not they are not understood. Their derived data are just plain wrong sometimes while their RAW data is fine.

Explain :-[

Well, the obvious example is the DR score on a sensor like the Nikon D800 - DxOMark reports that as 14.4 EV, while the sensor has a 14-bit analog-to-digital converter meaning a real, measured DR of 14.4 is electronically impossible for the sensor.  If you look at the raw data they actually measure, before their flawed method of normalization, it's 13.2 EV (which is, of course, very good...just not impossibly good).

Why is 14 a hard limit ? I understand that it's impossible to represent more than 2^14 different intensities but that's not what dynamic range is. DR is log2(saturation point) - log2( blackpoint). Why can't this be greater than the number of bits in the ADC converter ? .

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Re: More Big Megapixel Talk [CR1]
« Reply #171 on: October 03, 2012, 09:13:15 PM »

neuroanatomist

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Re: More Big Megapixel Talk [CR1]
« Reply #172 on: October 03, 2012, 09:37:29 PM »
Why is 14 a hard limit ? I understand that it's impossible to represent more than 2^14 different intensities but that's not what dynamic range is. DR is log2(saturation point) - log2( blackpoint). Why can't this be greater than the number of bits in the ADC converter ?

It could with a nonlinear ADC, except that almost all IC-based ADCs are linear.  So, while the analog DR is the delta between the full well capacity and the noise floor (in e-), a 14-bit ADC maps signal at the noise floor to 0 and signal at full well capacity to 16,383, binning intermediate e- values incrementally, subject to quantization error.
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elflord

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Re: More Big Megapixel Talk [CR1]
« Reply #173 on: October 03, 2012, 11:08:00 PM »
Why is 14 a hard limit ? I understand that it's impossible to represent more than 2^14 different intensities but that's not what dynamic range is. DR is log2(saturation point) - log2( blackpoint). Why can't this be greater than the number of bits in the ADC converter ?

It could with a nonlinear ADC, except that almost all IC-based ADCs are linear.  So, while the analog DR is the delta between the full well capacity and the noise floor (in e-), a 14-bit ADC maps signal at the noise floor to 0 and signal at full well capacity to 16,383, binning intermediate e- values incrementally, subject to quantization error.

You have the response (possibly nonlinear of the ADC). What about the response of the sensor itself to light ? Must this always be exactly linear ?

Also, if I pool four adjacent signals into one supersize pixel, how many bits do I have in my new "superpixel" ? Do I not have 56 bits ?

generalstuff

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Re: More Big Megapixel Talk [CR1]
« Reply #174 on: October 04, 2012, 02:05:10 AM »
Guys, no matter what facts you have or what you say it's not going to help much, lol.

Well, in this case they must blaime theirs own ignorance regarding multipel read outs and not
DXO meassurements.
Go to sensorgen, there you have all data ,FWC and read out noise



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caruser

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Re: More Big Megapixel Talk [CR1]
« Reply #175 on: October 04, 2012, 03:37:53 AM »
Why is 14 a hard limit ? I understand that it's impossible to represent more than 2^14 different intensities but that's not what dynamic range is. DR is log2(saturation point) - log2( blackpoint). Why can't this be greater than the number of bits in the ADC converter ?

It could with a nonlinear ADC, except that almost all IC-based ADCs are linear.  So, while the analog DR is the delta between the full well capacity and the noise floor (in e-), a 14-bit ADC maps signal at the noise floor to 0 and signal at full well capacity to 16,383, binning intermediate e- values incrementally, subject to quantization error.

You have the response (possibly nonlinear of the ADC). What about the response of the sensor itself to light ? Must this always be exactly linear ?

Also, if I pool four adjacent signals into one supersize pixel, how many bits do I have in my new "superpixel" ? Do I not have 56 bits ?

That would be too easy, no, when merging 4 pixels you gain (at best) two more bits, because 4 is 2^2 (where the exponent is the one we're interested in). Think about it, you have 4 times a value from 0 to X, so the combination gives you a value from 0 to X*4, which is two additional bits, not X^4 or whatever you need to go to 56 bits! Said differently, you can't multiply the bits by 4 when you multiply the pixels by 4 because the pixels are on a linear, and the bits on a logarithmic scale.

generalstuff

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Re: More Big Megapixel Talk [CR1]
« Reply #176 on: October 04, 2012, 03:53:03 AM »
Guys, no matter what facts you have or what you say it's not going to help much, lol.
I know, I know.  But...the windmill is right there, just sticking straight up out of the field and begging to be tilted at and charged...


Really, the D3x has a 12-bit ADC?  Quick, you'd better call Nobuyoshi Gokyu (President & CEO of Nikon, Inc., but I'm sure you know that) and tell him that the features page for the D3x, which states, "Fast 14-bit A/D conversion incorporated onto the image sensor," is wrong and needs to be corrected immediately, based on your thorough understanding of the read out from Nikon sensors.

So, if we can agree that Nikon is correct about their own D3x specifications, and that you, despite your extensive understanding and studying, are wrong about their D3x specifications, let's just say that the D3x has a 14-bit ADC and move on...

In that case, DxO's measurements show a very decent 12.84 EV of DR for the D3x.  Their 'Landscape Score', however, is an artifically inflated 13.65 EV - still technically possible (unlike the D800), but again, artifically inflated as a direct result of a flawed method of data analysis.

Study the subject, indeed.  Oh, puuullllleeeeeeeze.  It's almost as if I didn't have a day job that includes both analyzing quantitative image analysis data and managing a large group of scientists who do the same...  ::)
[/quote]





Sorry but you are wrong  :)

D3x sensor is the same as in  the Sony A900, there has been much discussion whether it is a 12 or 14-bit column ADC and if Nikon has changed it  . In  the Sony's sensor is it determined that  is a 12-bit  column ADC.

Whether it's  a 12 or 14 bit ADC in Nikon . In the d3x . D90, d7000, d800 it takes place two readouts of data and these  data are merged so the number of dynamic stops are higher than  the number of stops from a normal read out  to a  common ADC.

With Canons sensor layout it's different . Based on the 18MP APS-C pixel with a very good and very expensive external ADC - probably 16 bit  could give them better "more mega pixel camera " and  DR, if they can deal with the banding. One sensor expert always maintains that they (Canon) could deal with banding by leaving larger areas of masked black pixels (allows them to make the required changes in line by line and column by column gain.

So do not blaim DXO meassurements as incorrect  when  Canon  is showing  poor data  like DR and other meassurable parameters.

« Last Edit: October 04, 2012, 04:06:10 AM by generalstuff »

neuroanatomist

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Re: More Big Megapixel Talk [CR1]
« Reply #177 on: October 04, 2012, 05:52:19 AM »
So do not blaim DXO meassurements as incorrect  when  Canon  is showing  poor data  like DR and other meassurable parameters.

I'm not. Their measurements are fine. It's their analysis of those measurements, specifically the method of normalization which pushes values beyond the possible measured range, that is flawed (and their factor weighting for the overall score is a black box of 'weighted' combination where the weighting is undisclosed, and thus may not even be consistent). 

Nor am I saying that Canon's sensors have as good a DR as Nikon's, at least at low ISO (they don't, because their noise floor is too high, which diminishes in importance as gain is applied). 

But...it really doesn't matter, so I'll not continue to respond to your obviously specious statements, because:

D3x sensor is the same as in  the Sony A900, there has been much discussion whether it is a 12 or 14-bit column ADC and if Nikon has changed it  . In  the Sony's sensor is it determined that  is a 12-bit  column ADC.

Ok, so Nikon says it's 14-bit, but you say Nikon is lying and it's actually 12-bit....

Guys, no matter what facts you have or what you say it's not going to help much, lol.

I concede the point.  ;)
« Last Edit: October 04, 2012, 06:09:28 AM by neuroanatomist »
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Re: More Big Megapixel Talk [CR1]
« Reply #177 on: October 04, 2012, 05:52:19 AM »

elflord

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Re: More Big Megapixel Talk [CR1]
« Reply #178 on: October 04, 2012, 06:06:07 AM »


You have the response (possibly nonlinear of the ADC). What about the response of the sensor itself to light ? Must this always be exactly linear ?

Also, if I pool four adjacent signals into one supersize pixel, how many bits do I have in my new "superpixel" ? Do I not have 56 bits ?

That would be too easy, no, when merging 4 pixels you gain (at best) two more bits, because 4 is 2^2 (where the exponent is the one we're interested in). Think about it, you have 4 times a value from 0 to X, so the combination gives you a value from 0 to X*4, which is two additional bits, not X^4 or whatever you need to go to 56 bits! Said differently, you can't multiply the bits by 4 when you multiply the pixels by 4 because the pixels are on a linear, and the bits on a logarithmic scale.

Sorry, yes, that's what I meant (and what I hammered away at earlier). You get log2( number pixels merged).

It seems the conclusion though is that no, the number of bits in the ADC really is not a hard limit.

neuroanatomist

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Re: More Big Megapixel Talk [CR1]
« Reply #179 on: October 04, 2012, 06:20:30 AM »
It seems the conclusion though is that no, the number of bits in the ADC really is not a hard limit.

Agreed, at least that it's not a hard theoretical limit.  I believe it is a hard practical limit for the sensors under discussion, though.  Could they be nonlinear?  Unlikely - real data from previous sensors indicates linearity (e.g. Roger Clark's data), and as I stated, almost all IC-based ADC's are linear, except the very earliest ones.  As for binning, yes, you can gain DR, as well as sensitivity.  But you lose resolution - and since that's linear, not logarithmic, you trade a lot of resolution for that DR gain (having said that, many fluorescent imaging systems, where the signal is faint, do make just such a trade off, although the goal there is usually higher sensitivity, not the higher DR that comes with it).  If you interpolate back to full res, you get a softer image - and the D800 images are plenty sharp, so I don't think binning is going on here, either (for luminance, obviously color interpolation is a different story).
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Re: More Big Megapixel Talk [CR1]
« Reply #179 on: October 04, 2012, 06:20:30 AM »