Digital Camera Sensor Performane Summary updated Feb 3

Discussion in 'Digital Photography' started by Roger N. Clark (change username to rnclark), Feb 4, 2008.

  1. If you haven't visited this month, see:

    http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary

    I've added data for several newer cameras, added a new
    section on Apparent Image Quality (AIQ) along with models
    for constant megapixels and constant format size. What formerly
    looks like a scatter plot now is taking shape in that the
    pixel size and sensor format are showing trends. The models
    should now allow prediction of performance when new cameras
    come out. The new AIQ plot is Figure 9.

    Roger
     
    Roger N. Clark (change username to rnclark), Feb 4, 2008
    #1
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  2. Roger N. Clark (change username to rnclark) wrote:
    > If you haven't visited this month, see:
    >
    > http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
    >
    > I've added data for several newer cameras, added a new
    > section on Apparent Image Quality (AIQ) along with models
    > for constant megapixels and constant format size. What formerly
    > looks like a scatter plot now is taking shape in that the
    > pixel size and sensor format are showing trends. The models
    > should now allow prediction of performance when new cameras
    > come out. The new AIQ plot is Figure 9.
    >
    > Roger


    Most helpful, Roger, thanks. The D300 does look very good!

    Cheers,
    David
     
    David J Taylor, Feb 4, 2008
    #2
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  3. Roger N. Clark (change username to rnclark)

    nospam Guest

    In article <cYEpj.1450$>, David J Taylor
    <-this-bit.nor-this-bit.co.uk> wrote:

    > Roger N. Clark (change username to rnclark) wrote:
    > > If you haven't visited this month, see:
    > >
    > > http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
    > >
    > > I've added data for several newer cameras, added a new
    > > section on Apparent Image Quality (AIQ) along with models
    > > for constant megapixels and constant format size. What formerly
    > > looks like a scatter plot now is taking shape in that the
    > > pixel size and sensor format are showing trends. The models
    > > should now allow prediction of performance when new cameras
    > > come out. The new AIQ plot is Figure 9.

    >
    > Most helpful, Roger, thanks. The D300 does look very good!


    agreed, it's an excellent chart! one request - it would be nice to see
    a dashed line for the 1.5x cameras (nikon, pentax, sony).
     
    nospam, Feb 4, 2008
    #3
  4. nospam wrote:
    []
    >> Roger N. Clark (change username to rnclark) wrote:
    >>> If you haven't visited this month, see:
    >>>
    >>> http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary

    []
    > agreed, it's an excellent chart! one request - it would be nice to
    > see a dashed line for the 1.5x cameras (nikon, pentax, sony).


    Do you mean in figure 9?

    David
     
    David J Taylor, Feb 4, 2008
    #4
  5. Roger N. Clark (change username to rnclark)

    Paul Furman Guest

    Roger N. Clark (change username to rnclark) wrote:
    > If you haven't visited this month, see:
    >
    > http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
    >
    > I've added data for several newer cameras, added a new
    > section on Apparent Image Quality (AIQ) along with models
    > for constant megapixels and constant format size. What formerly
    > looks like a scatter plot now is taking shape in that the
    > pixel size and sensor format are showing trends. The models
    > should now allow prediction of performance when new cameras
    > come out. The new AIQ plot is Figure 9.


    Thanks, that'll take a while to absorb. The MTF is for a particular
    f/stop? The curved lines seem to suggest a theoretical benefit of
    increased MP count up to 60MP for a full frame sensor and a sweet spot
    of 30MP, right? Why does the 1DmIII have three diamonds? Is fine grained
    35mm film that bad at IQ?
     
    Paul Furman, Feb 4, 2008
    #5
  6. Roger N. Clark (change username to rnclark)

    nospam Guest

    In article <CTGpj.1501$>, David J
    Taylor <-this-bit.nor-this-bit.co.uk>
    wrote:

    > > agreed, it's an excellent chart! one request - it would be nice to
    > > see a dashed line for the 1.5x cameras (nikon, pentax, sony).

    >
    > Do you mean in figure 9?


    yep. although it's obvious where the line would be, it would be
    helpful for it to be there.
     
    nospam, Feb 4, 2008
    #6
  7. Roger N. Clark (change username to rnclark)

    Frank ess Guest

    nospam wrote:
    > In article <cYEpj.1450$>, David J
    > Taylor
    > <-this-bit.nor-this-bit.co.uk>
    > wrote:
    >
    >> Roger N. Clark (change username to rnclark) wrote:
    >>> If you haven't visited this month, see:
    >>>
    >>> http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
    >>>
    >>> I've added data for several newer cameras, added a new
    >>> section on Apparent Image Quality (AIQ) along with models
    >>> for constant megapixels and constant format size. What formerly
    >>> looks like a scatter plot now is taking shape in that the
    >>> pixel size and sensor format are showing trends. The models
    >>> should now allow prediction of performance when new cameras
    >>> come out. The new AIQ plot is Figure 9.

    >>
    >> Most helpful, Roger, thanks. The D300 does look very good!

    >
    > agreed, it's an excellent chart! one request - it would be nice to
    > see a dashed line for the 1.5x cameras (nikon, pentax, sony).


    I'd like to see a cost per Apparent Image Quality increment chart, by
    camera model.

    --
    Frank ess
     
    Frank ess, Feb 4, 2008
    #7
  8. Paul Furman wrote:
    > Roger N. Clark (change username to rnclark) wrote:
    >> If you haven't visited this month, see:
    >>
    >> http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
    >>
    >> I've added data for several newer cameras, added a new
    >> section on Apparent Image Quality (AIQ) along with models
    >> for constant megapixels and constant format size. What formerly
    >> looks like a scatter plot now is taking shape in that the
    >> pixel size and sensor format are showing trends. The models
    >> should now allow prediction of performance when new cameras
    >> come out. The new AIQ plot is Figure 9.

    >
    > Thanks, that'll take a while to absorb. The MTF is for a particular
    > f/stop?


    Yes, 50% MTF response for 2 indicated f/stops.
    The curves and key are labeled. The two limits used are f/8 and f/4.

    > The curved lines seem to suggest a theoretical benefit of
    > increased MP count up to 60MP for a full frame sensor and a sweet spot
    > of 30MP, right?


    Yes, that is what the model says. It would sure be interesting
    to see images from such a camera. The model also indicates
    that the 1.3x crop sensors will peak at about 12-megapixels
    (assuming f/8 diffraction limited lens performance).

    > Why does the 1DmIII have three diamonds?


    It has one (a little arrow points to the middle one).
    The other two are other sensors. Like the one to the
    right is a Kodak KAI-16000 CCD.

    > Is fine grained
    > 35mm film that bad at IQ?


    Yes, by the AIQ definition. Film resolves detail pretty
    well, but the noise, through film grain, is pretty bad.
    Other pages on my site show measurements of image noise on
    scanned film.

    Roger
     
    Roger N. Clark (change username to rnclark), Feb 5, 2008
    #8
  9. Re: Digital Camera Sensor: 14bit sucks?

    [A complimentary Cc of this posting was sent to
    Roger N. Clark (change username to rnclark)
    <>], who wrote in article <>:
    > If you haven't visited this month, see:
    >
    > http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
    >
    > I've added data for several newer cameras


    Thanks.

    What is very surprizing is how large is the improvement due to switch
    from 12-bit ADC to 14-bit: not *exactly* zero, but only 11%!

    Camera Full well Noise at ISO50 Dynamic range Sensel
    --------------------------------------------------------------------
    Canon 1DMII CMOS 79,900* 30.6 2611 8.2um
    Canon 1DMIII CMOS 70,500 24.4 2889 7.2um

    Most probably the "improvement" in noise is just due to lower area of
    a sensel, thus lower capacitance, thus larger voltage generated by
    each electron. So it looks like 14-bitness is 93% hoax: the ADC
    behaved as an ideal 10-bit ADC before, now it behaves as 10.15-bit...

    Puzzled,
    Ilya
     
    Ilya Zakharevich, Feb 7, 2008
    #9
  10. Re: Digital Camera Sensor: 14bit sucks?

    Ilya Zakharevich wrote:
    > [A complimentary Cc of this posting was sent to
    > Roger N. Clark (change username to rnclark)
    > <>], who wrote in article <>:
    >> If you haven't visited this month, see:
    >>
    >> http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
    >>
    >> I've added data for several newer cameras

    >
    > Thanks.
    >
    > What is very surprizing is how large is the improvement due to switch
    > from 12-bit ADC to 14-bit: not *exactly* zero, but only 11%!
    >
    > Camera Full well Noise at ISO50 Dynamic range Sensel
    > --------------------------------------------------------------------
    > Canon 1DMII CMOS 79,900* 30.6 2611 8.2um
    > Canon 1DMIII CMOS 70,500 24.4 2889 7.2um
    >
    > Most probably the "improvement" in noise is just due to lower area of
    > a sensel, thus lower capacitance, thus larger voltage generated by
    > each electron. So it looks like 14-bitness is 93% hoax: the ADC
    > behaved as an ideal 10-bit ADC before, now it behaves as 10.15-bit...
    >
    > Puzzled,
    > Ilya


    Try looking at more of the picture. The smaller pixel
    has less photons, so if the 1DIII used the same 12-bit ADC
    as in the 1DII, the higher read noise and lower full well
    capacity would result in a dynamic range 11% SMALLER than
    the 1DII, so overall, the 1DIII 14-bit ADC and read noise
    has improved about 22% at low ISOs. But that too is not the whole
    story. Look at higher ISOs, and the 1DIII read noise drops to
    2.1 electrons compared to the 1DII 3.9 electrons, about
    an 86% improvement, which helps high ISO imaging. That and
    greatly improved fixed pattern noise makes the new generations
    of DSLRs much better at high ISO imaging (both Canon and Nikon).

    Read noise is not related to pixel size, see Figure 3.

    "Hope this Helps"
    Roger
     
    Roger N. Clark (change username to rnclark), Feb 7, 2008
    #10
  11. Re: Digital Camera Sensor: 14bit sucks?

    Ilya Zakharevich <> wrote:
    >[A complimentary Cc of this posting was sent to
    >Roger N. Clark (change username to rnclark)
    ><>], who wrote in article <>:
    >> If you haven't visited this month, see:
    >>
    >> http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
    >>
    >> I've added data for several newer cameras

    >
    >Thanks.
    >
    >What is very surprizing is how large is the improvement due to switch
    >from 12-bit ADC to 14-bit: not *exactly* zero, but only 11%!
    >
    > Camera Full well Noise at ISO50 Dynamic range Sensel
    > --------------------------------------------------------------------
    > Canon 1DMII CMOS 79,900* 30.6 2611 8.2um
    > Canon 1DMIII CMOS 70,500 24.4 2889 7.2um
    >
    >Most probably the "improvement" in noise is just due to lower area of
    >a sensel, thus lower capacitance, thus larger voltage generated by
    >each electron. So it looks like 14-bitness is 93% hoax: the ADC
    >behaved as an ideal 10-bit ADC before, now it behaves as 10.15-bit...


    Changing from a 12 bit ADC to a 14 bit ADC does *not* change the
    dynamic range of the sensor.

    --
    Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
    Ukpeagvik (Barrow, Alaska)
     
    Floyd L. Davidson, Feb 7, 2008
    #11
  12. Re: Digital Camera Sensor: 14bit sucks?

    [A complimentary Cc of this posting was sent to
    Roger N. Clark (change username to rnclark)
    <>], who wrote in article <>:
    > > Camera Full well Noise at ISO50 Dynamic range Sensel
    > > --------------------------------------------------------------------
    > > Canon 1DMII CMOS 79,900* 30.6 2611 8.2um
    > > Canon 1DMIII CMOS 70,500 24.4 2889 7.2um
    > >
    > > Most probably the "improvement" in noise is just due to lower area of
    > > a sensel, thus lower capacitance, thus larger voltage generated by
    > > each electron. So it looks like 14-bitness is 93% hoax: the ADC
    > > behaved as an ideal 10-bit ADC before, now it behaves as 10.15-bit...


    > Try looking at more of the picture. The smaller pixel
    > has less photons, so if the 1DIII used the same 12-bit ADC
    > as in the 1DII, the higher read noise and lower full well
    > capacity would result in a dynamic range 11% SMALLER than
    > the 1DII


    It would help if you FINALLY get some clue about the relation of pixel
    size to capacitance to voltage.

    Photons do not come into the context of this table at all. Full well
    is measured in electrons; likewise for the noise. An electron
    added to a smaller sensel will generate higher voltage than when added
    to a larger sensel.

    > so overall, the 1DIII 14-bit ADC and read noise
    > has improved about 22% at low ISOs.


    As I said, with CORRECT arithmetic there is no improvement.

    > Look at higher ISOs, and the 1DIII read noise drops to
    > 2.1 electrons compared to the 1DII 3.9 electrons, about
    > an 86% improvement, which helps high ISO imaging.


    You know that THIS has nothing to do with high bit count. In the
    regime of the full well of about 4K electrons, 2 electron noise is
    "approximately 9-bits".

    Hope this helps,
    Ilya
     
    Ilya Zakharevich, Feb 7, 2008
    #12
  13. Re: Digital Camera Sensor: 14bit sucks?

    [A complimentary Cc of this posting was NOT [per weedlist] sent to
    Floyd L. Davidson
    <>], who wrote in article <>:

    > Changing from a 12 bit ADC to a 14 bit ADC does *not* change the
    > dynamic range of the sensor.


    Thanks, but no thanks. I'm not interested in definition games.

    What it COULD change was the dynamic range of the whole sensor/ADC etc
    pipeline. But it did not.

    Hope this helps,
    Ilya
     
    Ilya Zakharevich, Feb 7, 2008
    #13
  14. Re: Digital Camera Sensor: 14bit sucks?

    Ilya Zakharevich wrote:
    > [A complimentary Cc of this posting was sent to
    > Roger N. Clark (change username to rnclark)
    > <>], who wrote in article <>:
    >>> Camera Full well Noise at ISO50 Dynamic range Sensel
    >>> --------------------------------------------------------------------
    >>> Canon 1DMII CMOS 79,900* 30.6 2611 8.2um
    >>> Canon 1DMIII CMOS 70,500 24.4 2889 7.2um
    >>>
    >>> Most probably the "improvement" in noise is just due to lower area of
    >>> a sensel, thus lower capacitance, thus larger voltage generated by
    >>> each electron. So it looks like 14-bitness is 93% hoax: the ADC
    >>> behaved as an ideal 10-bit ADC before, now it behaves as 10.15-bit...

    >
    >> Try looking at more of the picture. The smaller pixel
    >> has less photons, so if the 1DIII used the same 12-bit ADC
    >> as in the 1DII, the higher read noise and lower full well
    >> capacity would result in a dynamic range 11% SMALLER than
    >> the 1DII

    >
    > It would help if you FINALLY get some clue about the relation of pixel
    > size to capacitance to voltage.
    >
    > Photons do not come into the context of this table at all. Full well
    > is measured in electrons; likewise for the noise. An electron
    > added to a smaller sensel will generate higher voltage than when added
    > to a larger sensel.
    >
    >> so overall, the 1DIII 14-bit ADC and read noise
    >> has improved about 22% at low ISOs.

    >
    > As I said, with CORRECT arithmetic there is no improvement.
    >
    >> Look at higher ISOs, and the 1DIII read noise drops to
    >> 2.1 electrons compared to the 1DII 3.9 electrons, about
    >> an 86% improvement, which helps high ISO imaging.

    >
    > You know that THIS has nothing to do with high bit count. In the
    > regime of the full well of about 4K electrons, 2 electron noise is
    > "approximately 9-bits".
    >
    > Hope this helps,
    > Ilya
    >
    >

    BS
     
    Roger N. Clark (change username to rnclark), Feb 8, 2008
    #14
  15. Roger N. Clark (change username to rnclark)

    John Navas Guest

    Re: Digital Camera Sensor: 14bit sucks?

    On Thu, 07 Feb 2008 19:16:33 -0700, "Roger N. Clark (change username to
    rnclark)" <> wrote in <>:

    >Ilya Zakharevich wrote:


    >> It would help if you FINALLY get some clue about the relation of pixel
    >> size to capacitance to voltage.
    >>
    >> Photons do not come into the context of this table at all. Full well
    >> is measured in electrons; likewise for the noise. An electron
    >> added to a smaller sensel will generate higher voltage than when added
    >> to a larger sensel.


    >> As I said, with CORRECT arithmetic there is no improvement.


    >> You know that THIS has nothing to do with high bit count. In the
    >> regime of the full well of about 4K electrons, 2 electron noise is
    >> "approximately 9-bits".


    >BS


    That may be, but I see quite a few unsupported assumptions in your work,
    so as interesting as it may be, I can't accept it at face value.

    --
    Best regards,
    John Navas
    Panasonic DMC-FZ8 (and several others)
     
    John Navas, Feb 8, 2008
    #15
  16. Re: Digital Camera Sensor: 14bit sucks?

    John Navas wrote:
    >
    > but I see quite a few unsupported assumptions in your work,
    >

    So what might be those "quite a few" be?
     
    Roger N. Clark (change username to rnclark), Feb 8, 2008
    #16
  17. Roger N. Clark (change username to rnclark)

    John Navas Guest

    Re: Digital Camera Sensor: 14bit sucks?

    On Thu, 07 Feb 2008 22:11:22 -0700, "Roger N. Clark (change username to
    rnclark)" <> wrote in <>:

    >John Navas wrote:
    >>
    >> but I see quite a few unsupported assumptions in your work,
    >>

    >So what might be those "quite a few" be?


    I don't have time to go through all of it, so here are a few things
    I noticed on my initial reading:

    The first paragraph is composed of unsupported claims. If it's intended
    to be a summary of the rest of the document, that should be stated. If
    instead you have citations, footnote numbers would be good. As it is,
    it reads like a set of unsupported starting assumptions.

    Photons aren't converted into electrons -- they stimulate the release of
    electrons, called photoelectrons.

    ALthough not currently used in digital cameras AFAIK, there are multiple
    electron sensors -- 1:1 is not ideal.

    You use your own definition of dynamic range.

    Read noise is affected by readout speed, which you seem to ignore other
    than for the A/D converter.

    Etc.

    The essence of scientific analysis is that we either make postulates
    (like "It turns out that the noise in good modern digital cameras is
    dominated by photon counting statistics, not other sources.") and then
    prove them, or accumulate evidence and draw conclusions from that
    evidence. Many or even most of things you say may be true, but that
    doesn't follow from your presentation.

    --
    Best regards,
    John Navas
    Panasonic DMC-FZ8 (and several others)
     
    John Navas, Feb 8, 2008
    #17
  18. Roger N. Clark (change username to rnclark)

    acl Guest

    Re: Digital Camera Sensor: 14bit sucks?

    On Feb 8, 10:38 am, John Navas <> wrote:
    > On Thu, 07 Feb 2008 22:11:22 -0700, "Roger N. Clark (change username to
    > rnclark)" <> wrote in <>:
    >
    > >John Navas wrote:

    >
    > >> but I see quite a few unsupported assumptions in your work,

    >
    > >So what might be those "quite a few" be?

    >
    > I don't have time to go through all of it, so here are a few things
    > I noticed on my initial reading:
    >
    > The first paragraph is composed of unsupported claims. If it's intended
    > to be a summary of the rest of the document, that should be stated. If
    > instead you have citations, footnote numbers would be good. As it is,
    > it reads like a set of unsupported starting assumptions.
    >
    > Photons aren't converted into electrons -- they stimulate the release of
    > electrons, called photoelectrons.


    Well if you want to be a pedant, they don't "stimulate" (like in a
    laser) but instead "excite" electrons; the photon is "absorbed". Then
    again, they're not "electrons", they're quasiparticles which we call
    "electrons" for brevity. And so on.
     
    acl, Feb 8, 2008
    #18
  19. Re: Digital Camera Sensor: 14bit sucks?

    John Navas wrote:
    > On Thu, 07 Feb 2008 22:11:22 -0700, "Roger N. Clark (change username to
    > rnclark)" <> wrote in <>:
    >
    >> John Navas wrote:
    >>> but I see quite a few unsupported assumptions in your work,
    >>>

    >> So what might be those "quite a few" be?

    >
    > I don't have time to go through all of it, so here are a few things
    > I noticed on my initial reading:
    >
    > The first paragraph is composed of unsupported claims. If it's intended
    > to be a summary of the rest of the document, that should be stated. If
    > instead you have citations, footnote numbers would be good. As it is,
    > it reads like a set of unsupported starting assumptions.


    There are over 35 refere3nces on the web page, many from sensor
    manufacturers. All the statements in the intro are supported
    by multiple references.

    > Photons aren't converted into electrons -- they stimulate the release of
    > electrons, called photoelectrons.


    This is semantics. Photons are absorbed, and that energy goes into
    exciting electrons so there is a 1:1 correspondence in
    photons to electrons. Once the photoelectrons are produced,
    they are simply called electrons. Read any of the manufacturers
    data sheets (many of which I reference) and you'll see
    full well capacities and read noise specified in electrons,
    not photoelectrons.

    > ALthough not currently used in digital cameras AFAIK, there are multiple
    > electron sensors -- 1:1 is not ideal.


    These are electron multiplying CCDs. One photon produces one
    photoelectron and that electron then gets multiplied. There is no
    change in quantum efficiency. It is a method used to effectively
    make read noise negligible. That was important when read noise
    was 15 or so electrons, but is less important now that other methods
    result in much lower read noise. And what relevance is this
    to the properties of current digital cameras, none of which
    use the technology.
    >
    > You use your own definition of dynamic range.


    No! That is the industry standard definition. I even give a reference
    to Hamamatsu, a sesnor manufacturer who gives the definition.


    > Read noise is affected by readout speed, which you seem to ignore other
    > than for the A/D converter.


    While you are correct, read noise is reduced by very slow and
    multiple correlated reads. In scientific sensors, often a
    many seconds are used to read out a 1-megapixel chip. But,
    again, that is irrelevant for two reasons: modern digital
    cameras (e.g. 2007 models) have already achieved extraordinarily
    low read noise, as low as about 2 electrons. And again,
    how is slow read relevant? The read noise is a measured
    property, whatever methods are used. The values for read noise
    on the web page are measured, not theoretical or modeled.
    >
    > Etc.
    >
    > The essence of scientific analysis is that we either make postulates
    > (like "It turns out that the noise in good modern digital cameras is
    > dominated by photon counting statistics, not other sources.") and then
    > prove them, or accumulate evidence and draw conclusions from that
    > evidence. Many or even most of things you say may be true, but that
    > doesn't follow from your presentation.


    Read the references. The fact that CCDs and CMOS sensors have noise that
    is dominated by photon noise is well established by multiple
    sources, from the sensor manufacturers themselves, to scientists
    working with the devices, to the amateur astronomers testing
    the devices.

    The title of the web page is "Digital Camera Sensor Performance Summary"
    not "This is why...."

    For the evidence of how this is determined, see references on the
    web page in question,
    http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
    and

    Procedures for Evaluating Digital Camera
    Sensor Noise, Dynamic Range, and Full Well Capacities;
    Canon 1D Mark II Analysis
    http://www.clarkvision.com/imagedetail/evaluation-1d2

    Digital Cameras:
    Counting Photons, Photometry, and Quantum Efficiency
    http://www.clarkvision.com/imagedetail/digital.photons.and.qe

    and references therein.

    Roger
     
    Roger N. Clark (change username to rnclark), Feb 8, 2008
    #19
  20. Roger N. Clark (change username to rnclark)

    John Navas Guest

    Re: Digital Camera Sensor: 14bit sucks?

    On Fri, 08 Feb 2008 07:53:00 -0700, "Roger N. Clark (change username to
    rnclark)" <> wrote in <>:

    >John Navas wrote:
    >> On Thu, 07 Feb 2008 22:11:22 -0700, "Roger N. Clark (change username to
    >> rnclark)" <> wrote in <>:
    >>
    >>> John Navas wrote:
    >>>> but I see quite a few unsupported assumptions in your work,
    >>>>
    >>> So what might be those "quite a few" be?

    >>
    >> I don't have time to go through all of it, so here are a few things
    >> I noticed on my initial reading:
    >>
    >> The first paragraph is composed of unsupported claims. If it's intended
    >> to be a summary of the rest of the document, that should be stated. If
    >> instead you have citations, footnote numbers would be good. As it is,
    >> it reads like a set of unsupported starting assumptions.

    >
    >There are over 35 refere3nces on the web page, many from sensor
    >manufacturers. All the statements in the intro are supported
    >by multiple references.


    That may be true, but there's no way to tell, and I doubt many are going
    to try to figure out which references are supposed to support which
    claim. As I wrote, footnotes would be good. Likewise a clear chain of
    reasoning, instead of sweeping summary statements.

    >> Photons aren't converted into electrons -- they stimulate the release of
    >> electrons, called photoelectrons.

    >
    >This is semantics. ...


    I respectfully disagree.

    >> ALthough not currently used in digital cameras AFAIK, there are multiple
    >> electron sensors -- 1:1 is not ideal.

    >
    >These are electron multiplying CCDs. One photon produces one
    >photoelectron and that electron then gets multiplied. There is no
    >change in quantum efficiency. It is a method used to effectively
    >make read noise negligible. That was important when read noise
    >was 15 or so electrons, but is less important now that other methods
    >result in much lower read noise. And what relevance is this
    >to the properties of current digital cameras, none of which
    >use the technology.


    The issue comes from your use of the term "ideal".

    >> Read noise is affected by readout speed, which you seem to ignore other
    >> than for the A/D converter.

    >
    >While you are correct, read noise is reduced by very slow and
    >multiple correlated reads. In scientific sensors, often a
    >many seconds are used to read out a 1-megapixel chip. But,
    >again, that is irrelevant for two reasons: modern digital
    >cameras (e.g. 2007 models) have already achieved extraordinarily
    >low read noise, as low as about 2 electrons. And again,
    >how is slow read relevant? The read noise is a measured
    >property, whatever methods are used. The values for read noise
    >on the web page are measured, not theoretical or modeled.


    Again, you're making claims without support.

    >Read the references.


    I've read many of them. The problem is that it's not at all clear which
    references are supposed to support which claim, if any references at
    all. Otherwise there's no good way to figure out whether your
    interpretation of those references is correct or not, an issue
    compounded by statements like photons being converted into electrons.

    >The fact that CCDs and CMOS sensors have noise that
    >is dominated by photon noise is well established by multiple
    >sources, from the sensor manufacturers themselves, to scientists
    >working with the devices, to the amateur astronomers testing
    >the devices.


    If so, then it should be straightforward to add citations/footnotes. As
    it is, it reads like unsupported claims. There's no way to tell what
    support exists for which claim. That you provide references is a very
    good start, but expecting your audience to either read all the
    references or just take you at face value greatly diminishes the
    potential weight and value of your work.

    >The title of the web page is "Digital Camera Sensor Performance Summary"
    >not "This is why...."
    >
    >For the evidence of how this is determined, see references on the
    >web page in question,
    >http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary
    >and


    Again, your audience shouldn't be left to figure out on their own which
    of your other pages is supposed to support which item.

    It's a pain to properly structure a chain of reasoning with supporting
    citations, but it is needed for any work that wants to be taken
    seriously.

    --
    Best regards,
    John Navas
    Panasonic DMC-FZ8 (and several others)
     
    John Navas, Feb 8, 2008
    #20
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