How many mp's to match resolution of 4x5 neg film cam?

Discussion in 'Digital Photography' started by Codex, Apr 29, 2005.

  1. Codex

    Codex Guest

    I'm sure this has been asked before but if any one knows the hard data
    can you please answer this question, I'm just curious to know the
    answer. Approximately how many mp's would a DC need to match the
    resolution of a 4x5 neg film camera?
    Codex, Apr 29, 2005
    #1
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  2. Codex

    Crownfield Guest

    Codex wrote:
    >
    > I'm sure this has been asked before


    right.

    codex, meet google.com
    google.com, meet codex

    <http://www.google.com/search?hl=en&q=4x5+film+megapixels&btnG=Google+Search>

    > but if any one knows the hard data
    > can you please answer this question, I'm just curious to know the
    > answer. Approximately how many mp's would a DC need to match the
    > resolution of a 4x5 neg film camera?
    Crownfield, Apr 29, 2005
    #2
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  3. Codex

    Codex Guest

    On Thu, 28 Apr 2005 23:15:20 -0700, Crownfield <>
    wrote:


    >right.
    >
    >codex, meet google.com
    >google.com, meet codex


    Yes, I've met google.com before but it's more fun asking on usenet.
    Just making conversation, you know?

    ><http://www.google.com/search?hl=en&q=4x5+film+megapixels&btnG=Google+Search>


    Now you've spoiled my fun. The answer is more than 200mp's. This
    thread is done. Thanks. :)
    Codex, Apr 29, 2005
    #3
  4. Codex

    Mark² Guest

    "Codex" <> wrote in message
    news:...
    > On Thu, 28 Apr 2005 23:15:20 -0700, Crownfield <>
    > wrote:
    >
    >
    >>right.
    >>
    >>codex, meet google.com
    >>google.com, meet codex

    >
    > Yes, I've met google.com before but it's more fun asking on usenet.
    > Just making conversation, you know?
    >
    >><http://www.google.com/search?hl=en&q=4x5+film+megapixels&btnG=Google+Search>

    >
    > Now you've spoiled my fun. The answer is more than 200mp's. This
    > thread is done. Thanks. :)


    Ya. -According to SOMEONE...
    The answer is entirely debatable.
    Mark², Apr 29, 2005
    #4
  5. Codex

    Guest

    Codex wrote:
    > I'm sure this has been asked before but if any one knows the hard

    data
    > can you please answer this question, I'm just curious to know the
    > answer. Approximately how many mp's would a DC need to match the
    > resolution of a 4x5 neg film camera?


    In french, this kind of question is called a "troll" (a scandinavian
    name for, somehow, nagging spirits), is there a similar word in
    english?

    But I'll answer you on the basis of Norman Koren data (see
    http://www.normankoren.com/Tutorials/MTF7.html ), who states that it
    takes around 100pixel by mm (ie 3600*2400px for 24*36) to have the same
    resolution as a scanned Provia100, that I find realistic (even
    pessimistic, because it does only consider resolution, not noise).

    Applied to 4*5" = 100*125mm, that rule of thumb would make
    10.000*12.500 = 125Mpix. Yes, it's quite a lot.
    Given the low loise in a big imaging chip (I assume you don't want a
    pocket camera???), you could decrease pixel count a bit, but the answer
    would still be "no way under 60Mpix". Still a lot.

    Did the troll have enough exercise?
    Greetings from France
    Nicolas
    , Apr 29, 2005
    #5
  6. wrote:

    > Codex wrote:
    >
    >>I'm sure this has been asked before but if any one knows the hard

    >
    > data
    >
    >>can you please answer this question, I'm just curious to know the
    >>answer. Approximately how many mp's would a DC need to match the
    >>resolution of a 4x5 neg film camera?

    >
    >
    > In french, this kind of question is called a "troll" (a scandinavian
    > name for, somehow, nagging spirits), is there a similar word in
    > english?
    >
    > But I'll answer you on the basis of Norman Koren data (see
    > http://www.normankoren.com/Tutorials/MTF7.html ), who states that it
    > takes around 100pixel by mm (ie 3600*2400px for 24*36) to have the same
    > resolution as a scanned Provia100, that I find realistic (even
    > pessimistic, because it does only consider resolution, not noise).
    >
    > Applied to 4*5" = 100*125mm, that rule of thumb would make
    > 10.000*12.500 = 125Mpix. Yes, it's quite a lot.
    > Given the low loise in a big imaging chip (I assume you don't want a
    > pocket camera???), you could decrease pixel count a bit, but the answer
    > would still be "no way under 60Mpix". Still a lot.


    The signal-to-noise issue is a good one. In noise testing as well
    as perception, the signal-to-noise of a DSLR allows improvement
    of spatial resolution by on the order of 2x, e.g. by
    Richardson-Lucy deconvolution, see:

    http://clarkvision.com/imagedetail/image-restoration1

    Film megapixel versus digital is film dependent. Fujichrome
    Velvia 4x5 is around 200 megapixels, see:

    http://www.clarkvision.com/imagedetail/scandetail.html

    Here are charts of film versus digital for many films
    and formats:

    http://www.clarkvision.com/imagedetail/film.vs.digital.1.html

    There are other articles about signal-to-noise, dynamic range,
    etc on the site. The effects of signal-to-noise on megapixel
    equivalent are discussed in the summary page:

    http://www.clarkvision.com/imagedetail/film.vs.digital.summary1.html

    Roger
    Roger N. Clark (change username to rnclark), Apr 29, 2005
    #6
  7. Codex

    james Guest

    In article <>,
    Codex <> wrote:
    >
    >
    >I'm sure this has been asked before but if any one knows the hard data
    >can you please answer this question, I'm just curious to know the
    >answer. Approximately how many mp's would a DC need to match the
    >resolution of a 4x5 neg film camera?


    Don't put the Crown Graphic or the Linhof in the yard sale just yet.
    james, Apr 29, 2005
    #7
  8. Codex

    Codex Guest

    On 29 Apr 2005 03:40:32 -0700, wrote:


    >Did the troll have enough exercise?
    >Greetings from France
    >Nicolas


    It wasn't a troll. A real troll said on a forum that 9mp matches 4x5
    neg and I called him a bullshitter and thus I turned up here to get
    the low down. Is that a troll? No.
    Codex, Apr 29, 2005
    #8
  9. Codex

    Codex Guest

    On Fri, 29 Apr 2005 17:47:32 GMT, (james)
    wrote:


    >Don't put the Crown Graphic or the Linhof in the yard sale just yet.
    >
    >


    I don't own one but would like to. Processing costs are expensive
    though. I own a Nikon 35mm and an Olympus DC. I don't even have my
    darkroom equipment anymore. I used to have a Beseler enlarger with
    Nikkor lense that could do 35mm or medium format negs. My kitchen was
    my darkroom. :)
    Codex, Apr 29, 2005
    #9
  10. Codex

    David Chien Guest

    Ask those that make them!
    www.betterlight.com
    www.phaseone.com

    ---

    Honestly, the way to do it is to ask what resolution do you expect to
    image on a 4x5 neg? If it's 50lp/mm (a very decent value for MF), then
    you'll get:
    4x5" = 102.8mm x 128.5mm by 50lp/mm = 5140 x 6425 pixels digital
    equivalent (approximate; ignores nyquest, analog vs. digital, etc.) = 33
    Megapixels

    Of course, the above two companies do sell high-end MF cameras that top
    100 megapixels, so you'll easily find something that'll match your
    current analog camera for resolution.
    David Chien, Apr 29, 2005
    #10
  11. Codex

    Chris Brown Guest

    In article <d4u85q$b33$>,
    David Chien <> wrote:
    >
    >Honestly, the way to do it is to ask what resolution do you expect to
    >image on a 4x5 neg? If it's 50lp/mm (a very decent value for MF), then
    >you'll get:
    >4x5" = 102.8mm x 128.5mm by 50lp/mm = 5140 x 6425 pixels digital
    >equivalent (approximate; ignores nyquest, analog vs. digital, etc.) = 33
    >Megapixels


    Ok, there are a couple of mistakes here. Firstly, a 4x5 sheet is actually
    only 120*96mm. Secondly, you can't represent a line *pair* by a single
    pixel. If we go for the "pefrect world" figure of 2 pixels per line-pair,
    you get:

    100 * 120 * 100 * 96

    ....which gives is 115 million pixels.

    In reality, you aren;t going to get pixels per line-pair in the digital
    world, so the actual *resolving power* is going to be higher than this, but
    this will be compensated for by digital pixels (assuming we're talking about
    a DSLR) being "cleaner", so in terms of overall image-quality, that 115
    megapixel figure is probably somewhere in the right ballpark. In terms of
    actual extinction resolution, the film should do a fair bit better.

    If we do the same calculation for 35mm, we get about 8 megapixels, which is
    a good match for the results people get from scanned 35mm slides, so it's
    probably not a bad estimate.
    Chris Brown, Apr 30, 2005
    #11
  12. Codex

    mike regish Guest

    I've still got mine.

    mike

    "Codex" <> wrote in message
    news:...
    > On Fri, 29 Apr 2005 17:47:32 GMT, (james)
    > wrote:
    >
    > I used to have a Beseler enlarger with
    > Nikkor lense that could do 35mm or medium format negs.
    mike regish, Apr 30, 2005
    #12
  13. [A complimentary Cc of this posting was sent to
    Codex
    <>], who wrote in article <>:
    > I'm sure this has been asked before but if any one knows the hard data
    > can you please answer this question, I'm just curious to know the
    > answer. Approximately how many mp's would a DC need to match the
    > resolution of a 4x5 neg film camera?


    If you mean "best possible resolution", then you already got many
    estimates. However, note that most large-format shots are not made at
    the "best resolution" f-stop. Thus *the particular shots* may be
    equivalent to much more modest megapixel count.

    Somewhat extreme example: starting from f/45, you may be able to get
    results which are not much worse even with current 4/3'' digicams (at
    low ISO sensitivity); at these f-stops the only thing which is
    stressed is the noise level of the film. And digicams have much lower
    noise level than film (even with much smaller sensor area).

    [Well, this estimate assumes that numbers for film noise on Roger Clark
    site are relevant. He still did not answer my queries about these
    numbers, so I would take the estimage above with a grain of salt.]

    Hope this helps,
    Ilya
    Ilya Zakharevich, Apr 30, 2005
    #13
  14. Ilya Zakharevich wrote:
    > [A complimentary Cc of this posting was sent to
    > Codex
    > <>], who wrote in article <>:
    >
    >>I'm sure this has been asked before but if any one knows the hard data
    >>can you please answer this question, I'm just curious to know the
    >>answer. Approximately how many mp's would a DC need to match the
    >>resolution of a 4x5 neg film camera?

    >
    >
    > If you mean "best possible resolution", then you already got many
    > estimates. However, note that most large-format shots are not made at
    > the "best resolution" f-stop. Thus *the particular shots* may be
    > equivalent to much more modest megapixel count.
    >
    > Somewhat extreme example: starting from f/45, you may be able to get
    > results which are not much worse even with current 4/3'' digicams (at
    > low ISO sensitivity); at these f-stops the only thing which is
    > stressed is the noise level of the film. And digicams have much lower
    > noise level than film (even with much smaller sensor area).


    Is this another theoretical result?
    Take a look at these tests on a 4x5 image at f/45:

    http://www.clarkvision.com/imagedetail/scandetail.html

    Have you ever seen a 30x40 inch digital print from a drum scanned
    velvia 4x5 image? You can walk right up and examine it at
    a few inches away and see extremely fine detail. Not even
    current high end pro DSLRs can match the the image detail of
    a 4x5 velvia, even at f/45.

    > [Well, this estimate assumes that numbers for film noise on Roger Clark
    > site are relevant. He still did not answer my queries about these
    > numbers, so I would take the estimage above with a grain of salt.]


    Why do you continue to attack me? What is it you have against me?
    I have tried to help you multiple times and you turn around and
    attack me. I have answered dozens of questions, and
    recently answered your questions on film noise, after answering
    previous questions on film noise. I don't understand your agenda.

    My numbers for film noise:
    http://clarkvision.com/imagedetail/digital.signal.to.noise
    I measure velvia to have a maximum S/N of 70, and the Canon
    1D Mark II DSLR 228. Ilya, what is your problem with these values,
    and do you have any actual data to prove a different result?

    Roger
    Roger N. Clark (change username to rnclark), Apr 30, 2005
    #14
  15. [A complimentary Cc of this posting was sent to
    Roger N. Clark (change username to rnclark)
    <>], who wrote in article <>:

    > > [Well, this estimate assumes that numbers for film noise on Roger Clark
    > > site are relevant. He still did not answer my queries about these
    > > numbers, so I would take the estimage above with a grain of salt.]


    > Why do you continue to attack me? What is it you have against me?


    I'm sorry if you consider this as a personal attack. I asked you a
    question, and did not get an anwer (until today, when you did answer).

    You have absolutely no obligation to answer my emails. However,
    without the answer the numbers on your site do not have an exact
    interpretation. Now, when I know the answer, they did.

    A lot of thanks. [And I hope you update your web page so that other
    people get the same advantage as I did. ;-]

    > My numbers for film noise:
    > http://clarkvision.com/imagedetail/digital.signal.to.noise
    > I measure velvia to have a maximum S/N of 70, and the Canon
    > 1D Mark II DSLR 228. Ilya, what is your problem with these values,
    > and do you have any actual data to prove a different result?


    I told you what are my problems with these numbers, and from your
    answers I understood that you understand well what are my problems.
    So why this question now?

    For the benefits of other people (until Roger writes this on his web
    page): the "film" numbers are for a square window with side 6.3
    microns; the "film" numbers are for density noise, not for luminance
    noise. [This is not the same as for digital sensors.]

    So the numbers for luminance S/N in a 8.2 microns window into the film
    (one used by other curves in the graph) should be about
    gamma*(8.2/6.3) times higher. Taking gamma for film of 1.5 (is it a
    good value?), one gets 1.95x higher values of S/N of film (using the
    same units as for digital sensor).

    [However, on other pages Roger shows that one *needs* to use smaller
    window into the film to get comparable resolution to one of the
    digital sensors. So it is quite probable that using a different
    window size for film *is* justified. However, IMO, comparing density
    noise of film with luminance noise of digital is not helpful.]

    Again: a lot of thanks for your web pages and your answers to my questions,
    Ilya
    Ilya Zakharevich, Apr 30, 2005
    #15
  16. Codex

    Chris Brown Guest

    In article <>,
    Roger N. Clark (change username to rnclark) <> wrote:
    >Ilya Zakharevich wrote:
    >
    >> [Well, this estimate assumes that numbers for film noise on Roger Clark
    >> site are relevant. He still did not answer my queries about these
    >> numbers, so I would take the estimage above with a grain of salt.]

    >
    >Why do you continue to attack me? What is it you have against me?
    >I have tried to help you multiple times and you turn around and
    >attack me. I have answered dozens of questions, and
    >recently answered your questions on film noise, after answering
    >previous questions on film noise. I don't understand your agenda.


    You inject reality into his make-believe world, by rudely pointing out that
    real 4x5 film actually captures far more detail than his pessimistic
    estimates that he needs it to deliver so that his magic sensor and lens made
    out of unobtanium can match it, and he sees that as rude.

    Just a guess. ;-)
    Chris Brown, Apr 30, 2005
    #16
  17. Ilya Zakharevich wrote:

    > [A complimentary Cc of this posting was sent to
    > Roger N. Clark (change username to rnclark)
    > <>], who wrote in article <>:
    >
    >
    >>>[Well, this estimate assumes that numbers for film noise on Roger Clark
    >>>site are relevant. He still did not answer my queries about these
    >>>numbers, so I would take the estimage above with a grain of salt.]

    >
    >
    >>Why do you continue to attack me? What is it you have against me?

    >
    >
    > I'm sorry if you consider this as a personal attack. I asked you a
    > question, and did not get an anwer (until today, when you did answer).


    You constantly take what I say and twist to being negative.
    What you do below is another example of this.

    > You have absolutely no obligation to answer my emails. However,
    > without the answer the numbers on your site do not have an exact
    > interpretation. Now, when I know the answer, they did.
    >
    > A lot of thanks. [And I hope you update your web page so that other
    > people get the same advantage as I did. ;-]
    >
    >
    >>My numbers for film noise:
    >>http://clarkvision.com/imagedetail/digital.signal.to.noise
    >>I measure velvia to have a maximum S/N of 70, and the Canon
    >>1D Mark II DSLR 228. Ilya, what is your problem with these values,
    >>and do you have any actual data to prove a different result?

    >
    > I told you what are my problems with these numbers, and from your
    > answers I understood that you understand well what are my problems.
    > So why this question now?
    >
    > For the benefits of other people (until Roger writes this on his web
    > page): the "film" numbers are for a square window with side 6.3
    > microns; the "film" numbers are for density noise, not for luminance
    > noise. [This is not the same as for digital sensors.]


    Here again, you take what I said and reinterpret it in a negative way.
    From your other statements that you have not yet made the switch
    from film, it seems this negative twisting of digital results
    is your way of not accepting the advancements of digital.

    Here are portions of the private email exchange:
    Ilya> And another question: was this noise for density, or for initial
    luminance?

    Roger> I calibrated the intensities using linear detectors, independently
    of the film. This way I calibrated the film's transfer curve.
    Example transfer curves are on my web site.

    So now you assume that the Linear detectors are the film scanner
    sensor. How then did I derive the film's transfer curve?
    The film's transfer curve is clearly shown on my web site.
    No, the linear detector was not the scanner, but a digital camera.
    This is described on the above page at:
    http://clarkvision.com/imagedetail/dynamicrange2

    >
    > So the numbers for luminance S/N in a 8.2 microns window into the film
    > (one used by other curves in the graph) should be about
    > gamma*(8.2/6.3) times higher. Taking gamma for film of 1.5 (is it a
    > good value?), one gets 1.95x higher values of S/N of film (using the
    > same units as for digital sensor).


    Film does not have a single gamma value. So this assumption is
    wrong in principle. While it may have close to a gamma
    value over a range in the mid portion of the characteristic curve,
    it still deviates from the value as you move closer to the
    ends (shoulder and toe). My measured curves of digital and
    film are shown at:
    http://clarkvision.com/imagedetail/dynamicrange2
    See Figure 8.

    If your equation gamma*(8.2/6.3) were applied to Velvia, Gamma~2
    in the mid point, we would get a factor of 2.6. My values for
    Velvia, at http://clarkvision.com/imagedetail/digital.signal.to.noise
    are about S/N = 40 in the mid range (3 stops down from maximum
    signal), thus you would say the film should be 40*2.6 ~ 100.
    At that same level, the 1D Mark II camera at ISO 100 produces
    a S/N ~135, just barely higher than the film. Then at higher
    intensities, the film would do better than the 1D mark II.
    Well, that is not what is observed in the real world: the
    1D Mark II images have much less noise than film. Here is
    an example of velvia (scan = 6 micron pixels) versus a
    canon D60 (6 micron pixels) (the D60 has significantly higher
    noise than the 1D II):
    http://www.clarkvision.com/imagedetail/film.vs.6mpxl.digital.html
    Note the noise, prominent in the bright areas, of the film,
    but the D60 is much smoother.

    > However, IMO, comparing density
    > noise of film with luminance noise of digital is not helpful.]


    But isn't that what one actually sees in the final image that you
    view? It is the final image that is important, not how you get there
    (film or digital).

    Roger
    Roger N. Clark (change username to rnclark), Apr 30, 2005
    #17
  18. [A complimentary Cc of this posting was sent to
    Roger N. Clark (change username to rnclark)
    <>], who wrote in article <>:

    > > I'm sorry if you consider this as a personal attack. I asked you a
    > > question, and did not get an anwer (until today, when you did answer).


    > You constantly take what I say and twist to being negative.


    I'm absolutely lost here... What is "negative"? My apology for not
    being able to write in such a way that you do not consider it as
    personal? Or what?

    > > For the benefits of other people (until Roger writes this on his web
    > > page): the "film" numbers are for a square window with side 6.3
    > > microns; the "film" numbers are for density noise, not for luminance
    > > noise. [This is not the same as for digital sensors.]


    > Here again, you take what I said and reinterpret it in a negative way.


    Roger, maybe it is not entirely my fault that what you wrote is not
    interpreted the way you intended it? [I still have no idea what is
    "negative" here...]

    > Ilya> And another question: was this noise for density, or for initial
    > luminance?
    >
    > Roger> I calibrated the intensities using linear detectors, independently
    > of the film. This way I calibrated the film's transfer curve.
    > Example transfer curves are on my web site.


    > So now you assume that the Linear detectors are the film scanner
    > sensor.


    So I did; was I wrong? So far, you did not answer... (And I still do
    not know what "This way I calibrated the film's transfer curve"
    means.)

    > How then did I derive the film's transfer curve?


    Sorry, I'm lost again: how this is related to the question at hand?

    > No, the linear detector was not the scanner, but a digital camera.
    > This is described on the above page at:
    > http://clarkvision.com/imagedetail/dynamicrange2


    And note that I still have no idea whether your numbers for film are
    for density, or for original luminance...

    > If your equation gamma*(8.2/6.3) were applied to Velvia, Gamma~2
    > in the mid point, we would get a factor of 2.6. My values for
    > Velvia, at http://clarkvision.com/imagedetail/digital.signal.to.noise
    > are about S/N = 40 in the mid range (3 stops down from maximum
    > signal)


    Are we looking at the same image? What I see on

    http://clarkvision.com/imagedetail/digital.signal.to.noise/digital-s-to-n.v1.gif

    is the maximum at about 51e3 DN; I assume it is white (100% gray); I
    would not go down 3 stops (to 12.5% gray), but to 18% gray, or 9e3
    DN. The S/N value I see is 16. At 12.5% gray it is closer to 8.

    Where did you take S/N = 40 from?

    > > However, IMO, comparing density
    > > noise of film with luminance noise of digital is not helpful.]


    > But isn't that what one actually sees in the final image that you
    > view? It is the final image that is important, not how you get there
    > (film or digital).


    Let me do it slowly: you want to say that you want to compare digital
    image at a correct gamma with a film image scanned at wrong gamma?
    I'm completely lost again at what kind of digital workflow you
    consider for your slide scans...

    I hope there is some confusion and we are talking about something
    different...

    Thanks,
    Ilya
    Ilya Zakharevich, May 1, 2005
    #18
  19. Ilya Zakharevich wrote:
    > [A complimentary Cc of this posting was sent to
    > Roger N. Clark (change username to rnclark)
    > <>], who wrote in article <>:
    >
    >
    >>>I'm sorry if you consider this as a personal attack. I asked you a
    >>>question, and did not get an anwer (until today, when you did answer).

    >
    >>You constantly take what I say and twist to being negative.

    >
    > I'm absolutely lost here... What is "negative"? My apology for not
    > being able to write in such a way that you do not consider it as
    > personal? Or what?


    Ilya,
    This newsgroup is commonly disrupted by trolls. One thing they
    do is personal attacks, telling people they are idiots, stupid,
    etc. Often this occurs in film versus digital wars. Then
    others tune out, or tell others to stop feeding the troll.
    I usually tune out, but I have had been in long battles with
    at least one troll. Some of your responses have been troll like,
    but I sincerely do not believe you are a troll. I believe
    you have a different point of view which I think I can learn
    from, and I hope visa versa. The internet can be quite
    impersonal, and people sometimes say things they would never
    say face to face. Here are some examples from your
    emails (in this newsgroup and personal emails to me):

    "Yes, I suspected that you would answer something like this; until some
    numeric "pseudo-scientific" explanation is available..."

    "What planet are you on?"

    "Where did you learn your excellent arguing technique? What I blame
    you is that your data is almost an order of magnitude off."

    And in the current exchange:
    "Well, this estimate assumes that numbers for film noise on Roger Clark
    site are relevant. He still did not answer my queries about these
    numbers, so I would take the estimage above with a grain of salt."

    In this last exchange you use the fact that I haven't answered an email
    to imply the results are wrong. I do have a life beyond this newsgroup.
    Besides a heavy workload, I did take a 2+ week vacation to
    Australia and New Zealand, and did not answer any emails while
    I was away (that was great-no computers!). Another way to reword
    to something like the last statement above would be:

    The numbers for the S/N of Velvia on Roger Clark's web site imply
    xyz, but does anyone know of similar data that agrees with this?
    I am unclear if Roger's numbers refer to density or original scene
    intensity.

    See the difference?

    > Roger, maybe it is not entirely my fault that what you wrote is not
    > interpreted the way you intended it?


    I agree with this! The problem with my web site I do not have enough
    time to really do it right. But I try to take constructive
    criticisms and comments and improve the web pages. Many people in
    this newsgroup have asked questions, and a few have pointed out mistakes
    (fortunately minor ones so far).

    That is why, instead of responding to tear down. you should respond with
    a more detailed question, or like in this thread, when you say I don't
    understand this. Keep the discussion on the technical issues at hand
    and not on the personal side. Everyone makes mistakes, and no one is
    perfect. By keeping a civil discussion everyone can learn.

    >>Ilya> And another question: was this noise for density, or for initial
    >>luminance?
    >>
    >>Roger> I calibrated the intensities using linear detectors, independently
    >>of the film. This way I calibrated the film's transfer curve.
    >>Example transfer curves are on my web site.

    >
    >>So now you assume that the Linear detectors are the film scanner
    >>sensor.

    >
    > So I did; was I wrong? So far, you did not answer... (And I still do
    > not know what "This way I calibrated the film's transfer curve"
    > means.)


    I did answer:
    "No, the linear detector was not the scanner, but a digital camera."
    which you quote below.


    > Sorry, I'm lost again: how this is related to the question at hand?


    This is a good response. It is not personal and it puts the
    burden on me to clarify what I have said. I'll do so below.

    >>No, the linear detector was not the scanner, but a digital camera.
    >>This is described on the above page at:
    >>http://clarkvision.com/imagedetail/dynamicrange2

    >
    > And note that I still have no idea whether your numbers for film are
    > for density, or for original luminance...


    This page:
    http://clarkvision.com/imagedetail/dynamicrange2
    Figure 8:
    http://clarkvision.com/imagedetail/dynamicrange2/dynamic-range-tfcn-film-1.gif

    Shows the curve shape for Velvia. This is a log-log
    plot and the slope of the curve is the gamma. So if film had a
    constant gamma, the transfer curve would be a straight line.
    If you did a google groups search, you would see a few months ago
    when I was trying to come up with a mathematical relationship
    for these curves. Several made suggestions, but none were good enough
    in my opinion. I even tried a many term polynomial. In the end
    I use piecewise local functions over narrow regions and did calculations
    by hand to convert film scan data to linear original scene
    intensity. Notice the horizontal axis on this plot is labeled
    "Scene Intensity." This is the same scale as the plot you
    refer to below:
    http://clarkvision.com/imagedetail/digital.signal.to.noise/digital-s-to-n.v1.gif
    that is labeled "Linear Intensity." Both are the original scene
    intensity in linear units. This is well described on the
    http://clarkvision.com/imagedetail/dynamicrange2
    (in fact people in this newsgroup had a lot of input improving that
    very discussion.) Using the transfer curve from density to
    original scene intensity, I converted the film scan values to
    original scene intensity. I did this only for a few points on the
    plot because it is so laborious.


    >>If your equation gamma*(8.2/6.3) were applied to Velvia, Gamma~2
    >>in the mid point, we would get a factor of 2.6. My values for
    >>Velvia, at http://clarkvision.com/imagedetail/digital.signal.to.noise
    >>are about S/N = 40 in the mid range (3 stops down from maximum
    >>signal)

    >
    > Are we looking at the same image? What I see on
    >
    > http://clarkvision.com/imagedetail/digital.signal.to.noise/digital-s-to-n.v1.gif
    >
    > is the maximum at about 51e3 DN; I assume it is white (100% gray); I
    > would not go down 3 stops (to 12.5% gray), but to 18% gray, or 9e3
    > DN. The S/N value I see is 16. At 12.5% gray it is closer to 8.
    >
    > Where did you take S/N = 40 from?


    The maximum signal is ~65500 (the film was exposed so that the brightest
    white paper was as close to the limit as I could get.
    18% of 65500 ~ 11800. Read that on the horizontal axis on
    the digital-s-to-n.v1.gif plot. The Velvia line is between S/N 20 and 24
    on the vertical axis.

    >>>However, IMO, comparing density
    >>>noise of film with luminance noise of digital is not helpful.]

    >
    >>But isn't that what one actually sees in the final image that you
    >>view? It is the final image that is important, not how you get there
    >>(film or digital).

    >
    > Let me do it slowly: you want to say that you want to compare digital
    > image at a correct gamma with a film image scanned at wrong gamma?
    > I'm completely lost again at what kind of digital workflow you
    > consider for your slide scans...


    I hope it is clear now the original scene intensity was used and
    that film density was converted correctly. But I personally am
    not convinced this is correct way to do things, as we do not view
    images converted to original scene intensity. We view them after this
    complex function is applied to the original scene intensity. This
    gets down to how people perceive images and noise in images.
    But that is a future research topic, and much more subjective
    than the mathematical linear scene intensity way.

    Does this clear things up enough on the topic?

    Roger
    Roger N. Clark (change username to rnclark), May 1, 2005
    #19
  20. Codex

    Mark² Guest

    Top-posted since this is the only comment...

    Roger,

    I commend you on your patience and civility.
    Far beyond what I could muster were I in your place (in this discussion).

    Well done.
    -Mark

    "Roger N. Clark (change username to rnclark)" <> wrote in
    message news:...
    > Ilya Zakharevich wrote:
    >> [A complimentary Cc of this posting was sent to
    >> Roger N. Clark (change username to rnclark)
    >> <>], who wrote in article <>:
    >>
    >>
    >>>>I'm sorry if you consider this as a personal attack. I asked you a
    >>>>question, and did not get an anwer (until today, when you did answer).

    >>
    >>>You constantly take what I say and twist to being negative.

    >>
    >> I'm absolutely lost here... What is "negative"? My apology for not
    >> being able to write in such a way that you do not consider it as
    >> personal? Or what?

    >
    > Ilya,
    > This newsgroup is commonly disrupted by trolls. One thing they
    > do is personal attacks, telling people they are idiots, stupid,
    > etc. Often this occurs in film versus digital wars. Then
    > others tune out, or tell others to stop feeding the troll.
    > I usually tune out, but I have had been in long battles with
    > at least one troll. Some of your responses have been troll like,
    > but I sincerely do not believe you are a troll. I believe
    > you have a different point of view which I think I can learn
    > from, and I hope visa versa. The internet can be quite
    > impersonal, and people sometimes say things they would never
    > say face to face. Here are some examples from your
    > emails (in this newsgroup and personal emails to me):
    >
    > "Yes, I suspected that you would answer something like this; until some
    > numeric "pseudo-scientific" explanation is available..."
    >
    > "What planet are you on?"
    >
    > "Where did you learn your excellent arguing technique? What I blame
    > you is that your data is almost an order of magnitude off."
    >
    > And in the current exchange:
    > "Well, this estimate assumes that numbers for film noise on Roger Clark
    > site are relevant. He still did not answer my queries about these
    > numbers, so I would take the estimage above with a grain of salt."
    >
    > In this last exchange you use the fact that I haven't answered an email
    > to imply the results are wrong. I do have a life beyond this newsgroup.
    > Besides a heavy workload, I did take a 2+ week vacation to
    > Australia and New Zealand, and did not answer any emails while
    > I was away (that was great-no computers!). Another way to reword
    > to something like the last statement above would be:
    >
    > The numbers for the S/N of Velvia on Roger Clark's web site imply
    > xyz, but does anyone know of similar data that agrees with this?
    > I am unclear if Roger's numbers refer to density or original scene
    > intensity.
    >
    > See the difference?
    >
    >> Roger, maybe it is not entirely my fault that what you wrote is not
    >> interpreted the way you intended it?

    >
    > I agree with this! The problem with my web site I do not have enough
    > time to really do it right. But I try to take constructive
    > criticisms and comments and improve the web pages. Many people in
    > this newsgroup have asked questions, and a few have pointed out mistakes
    > (fortunately minor ones so far).
    >
    > That is why, instead of responding to tear down. you should respond with
    > a more detailed question, or like in this thread, when you say I don't
    > understand this. Keep the discussion on the technical issues at hand
    > and not on the personal side. Everyone makes mistakes, and no one is
    > perfect. By keeping a civil discussion everyone can learn.
    >
    >>>Ilya> And another question: was this noise for density, or for initial
    >>>luminance?
    >>>
    >>>Roger> I calibrated the intensities using linear detectors, independently
    >>>of the film. This way I calibrated the film's transfer curve.
    >>>Example transfer curves are on my web site.

    >>
    >>>So now you assume that the Linear detectors are the film scanner
    >>>sensor.

    >>
    >> So I did; was I wrong? So far, you did not answer... (And I still do
    >> not know what "This way I calibrated the film's transfer curve"
    >> means.)

    >
    > I did answer:
    > "No, the linear detector was not the scanner, but a digital camera."
    > which you quote below.
    >
    >
    >> Sorry, I'm lost again: how this is related to the question at hand?

    >
    > This is a good response. It is not personal and it puts the
    > burden on me to clarify what I have said. I'll do so below.
    >
    >>>No, the linear detector was not the scanner, but a digital camera.
    >>>This is described on the above page at:
    >>>http://clarkvision.com/imagedetail/dynamicrange2

    >>
    >> And note that I still have no idea whether your numbers for film are
    >> for density, or for original luminance...

    >
    > This page:
    > http://clarkvision.com/imagedetail/dynamicrange2
    > Figure 8:
    > http://clarkvision.com/imagedetail/dynamicrange2/dynamic-range-tfcn-film-1.gif
    >
    > Shows the curve shape for Velvia. This is a log-log
    > plot and the slope of the curve is the gamma. So if film had a
    > constant gamma, the transfer curve would be a straight line.
    > If you did a google groups search, you would see a few months ago
    > when I was trying to come up with a mathematical relationship
    > for these curves. Several made suggestions, but none were good enough
    > in my opinion. I even tried a many term polynomial. In the end
    > I use piecewise local functions over narrow regions and did calculations
    > by hand to convert film scan data to linear original scene
    > intensity. Notice the horizontal axis on this plot is labeled
    > "Scene Intensity." This is the same scale as the plot you
    > refer to below:
    > http://clarkvision.com/imagedetail/digital.signal.to.noise/digital-s-to-n.v1.gif
    > that is labeled "Linear Intensity." Both are the original scene
    > intensity in linear units. This is well described on the
    > http://clarkvision.com/imagedetail/dynamicrange2
    > (in fact people in this newsgroup had a lot of input improving that
    > very discussion.) Using the transfer curve from density to
    > original scene intensity, I converted the film scan values to
    > original scene intensity. I did this only for a few points on the
    > plot because it is so laborious.
    >
    >
    >>>If your equation gamma*(8.2/6.3) were applied to Velvia, Gamma~2
    >>>in the mid point, we would get a factor of 2.6. My values for
    >>>Velvia, at http://clarkvision.com/imagedetail/digital.signal.to.noise
    >>>are about S/N = 40 in the mid range (3 stops down from maximum
    >>>signal)

    >>
    >> Are we looking at the same image? What I see on
    >>
    >>
    >> http://clarkvision.com/imagedetail/digital.signal.to.noise/digital-s-to-n.v1.gif
    >>
    >> is the maximum at about 51e3 DN; I assume it is white (100% gray); I
    >> would not go down 3 stops (to 12.5% gray), but to 18% gray, or 9e3
    >> DN. The S/N value I see is 16. At 12.5% gray it is closer to 8.
    >>
    >> Where did you take S/N = 40 from?

    >
    > The maximum signal is ~65500 (the film was exposed so that the brightest
    > white paper was as close to the limit as I could get.
    > 18% of 65500 ~ 11800. Read that on the horizontal axis on
    > the digital-s-to-n.v1.gif plot. The Velvia line is between S/N 20 and 24
    > on the vertical axis.
    >
    >>>>However, IMO, comparing density
    >>>>noise of film with luminance noise of digital is not helpful.]

    >>
    >>>But isn't that what one actually sees in the final image that you
    >>>view? It is the final image that is important, not how you get there
    >>>(film or digital).

    >>
    >> Let me do it slowly: you want to say that you want to compare digital
    >> image at a correct gamma with a film image scanned at wrong gamma?
    >> I'm completely lost again at what kind of digital workflow you
    >> consider for your slide scans...

    >
    > I hope it is clear now the original scene intensity was used and
    > that film density was converted correctly. But I personally am
    > not convinced this is correct way to do things, as we do not view
    > images converted to original scene intensity. We view them after this
    > complex function is applied to the original scene intensity. This
    > gets down to how people perceive images and noise in images.
    > But that is a future research topic, and much more subjective
    > than the mathematical linear scene intensity way.
    >
    > Does this clear things up enough on the topic?
    >
    > Roger
    Mark², May 1, 2005
    #20
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