low light

Discussion in 'Digital Photography' started by ipy2006, Mar 7, 2007.

  1. "Paul Rubin" <http://> wrote:
    > "David J. Littleboy" <> writes:
    >> I'm not seeing pattern noise in pushed images. Here's a 5D ISO 3200 file
    >> pushed 3 stops. Straight from Lightroom with noise reduction (and
    >> sharpening) turned off.
    >>
    >> http://www.pbase.com/davidjl/image/75374090/original

    >
    > You mean this is at 25,600?


    Exactly!

    > Pretty cool. I've seen TMZ pushed to
    > that speed and maybe the grain isn't worse, but the TMZ has no
    > tonality to speak of with that much pushing.


    I wonder if you are comparing apples to apples: that's a 100% crop from at
    12.7MP original. Even with that much noise, that's a lot of pixels. I'd
    think pushed film viewed at that resolution would be a major disaster.

    David J. Littleboy
    Tokyo, Japan
     
    David J. Littleboy, Mar 9, 2007
    #61
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  2. ipy2006

    ray Guest

    On Thu, 08 Mar 2007 13:24:03 -0800, Scott W wrote:

    > On Mar 8, 7:45 am, ray <> wrote:
    >> Since I don't have $1500 to blow on a digital SLR, I don't plan on doing
    >> my own comparison tests any time soon. I will be experimenting a little
    >> with my Kodak P850 to see what it's limitations are.

    > The Kodak may be able to produce a good looking image but it will not
    > come
    > close to the ISO performance that a DSLR will have, its sensor is just
    > too
    > small for that. It would be a mistake to judge what a DLSR is capable
    > of based on a point and shoot digital. The point and shoot cameras
    > that I have are pretty much limited to ISO 100 or less.


    Those are obvious points. Manual says the P850 will do iso 800 at 1.2 mp -
    400 otherwise. Certainly I would not judge what a dslr costing several
    times more by it. It's what I have, and happens to fit my current
    requirements better than a larger camera. I've just not had time to do
    much experimenting yet.

    >
    > To see just how much better a DSLR is first look at how the P850 does
    > at ISO 400
    > <http://www.dpreview.com/reviews/kodakp850/page11.asp>
    > Now look at how the a number of DLSRs do at ISO 800 and 1600
    > <http://www.dpreview.com/reviews/canoneos400d/page27.asp>
    >
    >


    One thing I note is that they advise shooting raw with the P850 at 400 - I
    routinely shoot raw on the P850 - something you can't do with many P&S
    cameras.

    >>I also have my trusty
    >> old Minolta SRT202 which I still put a roll through every once in a while
    >> - particularly doing wildlife shots at Yellowstone. I've not much doubt
    >> that under ideal conditions digital produces shots that are quite fine
    >> enough.

    > The reality is that a DSLR is far better at getting the good shots
    > when conditions are not idea, it is far better in low light and it is
    > far better when white balance might be tricky.


    That's what everyone seems to be saying.

    >
    >>The OP did not state (as I recall) whether the ultimate product
    >> would be files for editing on the computer or prints - I suspect that
    >> could easily swing the pendulum one way or the other.

    > Does not matter if you are going for prints or files a DSLR will do
    > way better in low
    > light.
    >
    >> BTW - I've produced
    >> shots from a 1mp Kodak DC210+ printed to 8x10 that look pretty damned good
    >> - but that was, again, under the best of circumstances.

    >
    > I have never gotten a 8 x 10 print from a 1 MP camera that I really
    > liked, they always looked really soft to me.
    >
    >
    >> I don't often use high ISO - I hope, as I said, to do some shooting in
    >> that area as time permits.- Hide quoted text -

    >
    > If you use either film or your point and shoot you will likely get
    > frustrated pretty fast,
    > unless you do B/W and really like grain, some people do.


    What I do is a lot of hiking and snowshoeing. I don't relish packing ten
    pounds of dslr and lenses along. For right now, the P850 seems to fill the
    bill. I don't do much B/W, I don't care for a lot of grain, I fairly
    frequently shoot wildlife at some distance, so will use a big zoom. Doubt
    I will get much frustrated - I believe I know what to expect - I've been
    using digital for a number of years - Kodak DC210+; Minolta S414; now the
    P850. I'll be sure and let you know if my frustration level gets out of
    control.


    >
    > Scott
     
    ray, Mar 9, 2007
    #62
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  3. ipy2006

    John Sheehy Guest

    "David J. Littleboy" <> wrote in
    news:esq8u8$9tm$:

    > In the 5D and 1Dmk2, the ISO 100 read noise looks to me to be
    > dominated by quantization errors;


    The standard deviation of an ISO 100 blackframe is about 1.26 ADU on a
    mkII, and 1.97 on a 5D (it's 0.9 ADU on the Pentax K10D). These are all
    quite a bit more than what is possible with quantization, and the ranges
    near black are where quantization is potentially most harmful.

    With the 14-bit 1DmkIII, the blackframe read noise at ISO 100 is 4.88
    ADU; not an improvement over the 1.26 of the 12-bit successor, and a hint
    that the mkII's 1.26 has nothing much to do with posterization (and how
    do you posterize black, anyway?).

    > the bit depth of the A/D converter
    > is two bits shy of what's needed, maybe three.


    It's definitely shy of what is usable within the sensor wells. We really
    can't tell at what point in the signal chain the high read noise (in
    electrons) comes from, but it is really there, so even if sensor wells
    are only limited by shot noise (and dark current noise, when applicable),
    the *camera* is still subjected to high read noise. The blackframe read
    noise at ISO 100 is generally in the 20 to 30 electron range. That means
    that two neighboring pixels could be as much as 100 electrons off, as far
    as their recorded and real differences are concerned.

    > The dynamic range at
    > ISO 100 to 400 is simply consistent with a 12-bit A/D converter.


    There really aren't that many samples of unique camera arrangements where
    you can observe one effect in isolation. We are victims of all kinds of
    coincidences in our observations.

    Anyway, regardless whether its the ADC, or the first amplifiers, the
    camera, somewhere, is picking up tremendous read noise, as measured in
    relative signal electrons, at the lowest ISOs electrons. You don't need
    more than 12 bits to get more DR out of these cameras; you need less read
    noise. You want just enough read noise to dither away any posterization.
    There is *far* more than what is needed for that in current cameras.

    > It's
    > only at ISO 800 and above that other noise sources intrude.
    >
    > That's why the D200 has the same ISO 100 dynamic range as the 5D.


    Does it? Most of the tests I've seen are about the RAW conversions,
    which tend to equalize things a bit; not RAW comparisons. The D200 may
    have less shot noise, but I think it also has more read noise, IIRC, and
    stronger banding noise (horizontal, not vertical as in those high-
    contrast edge problems), hidden by even stronger 2D random read noise.
    Nikon also clips their RAW data at the blackpoint; not a very good idea
    if you're really interested in clean deep shadows.

    >> Shot noise is
    >> the least of our digital imaging problems, IMO, especially with large
    >> sensors.

    >
    > I'm not seeing pattern noise in pused images. Here's a 5D ISO 3200
    > file pushed 3 stops. Straight from Lightroom with noise reduction (and
    > sharpening) turned off.
    >
    > http://www.pbase.com/davidjl/image/75374090/original


    There's a strong horizontal banding component there. Load it into
    photoshop, and open the motion blur tool. Set it to 0 degrees, and 50
    pixels. Then, change it to 90 degrees. See the difference? The
    horizontal blur creates much stronger horizontal streaks than the
    vertical does vertical, because there is horizontal streaking in the
    image, the pattern of which is masked by the more random 2D noise, but
    the strength of which is not.

    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    John Sheehy, Mar 9, 2007
    #63
  4. ipy2006

    acl Guest

    On Mar 9, 5:30 am, John Sheehy <> wrote:

    > which tend to equalize things a bit; not RAW comparisons. The D200 may
    > have less shot noise, but I think it also has more read noise, IIRC, and
    > stronger banding noise (horizontal, not vertical as in those high-
    > contrast edge problems), hidden by even stronger 2D random read noise.


    Where did you see this horizontal banding? I've never seen anything
    like that in my raw files, only vertical bands, eg here:
    http://www.pbase.com/al599/image/74719850
    I once took a black frame, dumped the data using dcraw, and then
    looked at the fourier transform of parts of the frame, and saw a
    smoothed spike indicating patterns periodic in the horizontal
    direction (ie vertical banding). But that was what I was looking for
    so maybe I missed something. Or maybe it is dcraw. I don't know. So,
    how did you see horizontal banding?

    > Nikon also clips their RAW data at the blackpoint; not a very good idea
    > if you're really interested in clean deep shadows.
    >
     
    acl, Mar 9, 2007
    #64
  5. ipy2006

    John Sheehy Guest

    "acl" <> wrote in
    news::

    > Where did you see this horizontal banding?


    It was not readily visible in the D200, for the reason I mentioned. The
    ratio of 2D noise to 1D noise determines how well you can see the 1D noise.
    I extracted the 1D components from the image, from an unilluminated area,
    and the intensity was actually greater than with my Canon 20D, which has a
    reputation for banding at high ISOs. I subsequently did the same for
    several cameras by various manufacturers, and found that they all had
    banding, and all had stronger banding than the 20D, but their 2D random
    noise was so much more so that the banding was masked.

    By banding, I mean offsets in the RAW data on a line-by-line basis, visible
    or not. Even when banding is not visible as "banding", it's removal still
    makes the remaining noise look much more natural (except, of course, for
    the inherent pixel grid of both the signal and noise), despite the fact
    that the standard deviation may drop by less than 1%. Any patterned or 1D
    noise, is much more destructive per unit of standard deviation, than 2D
    random noise. Even binning and downsampling fail to reduce 1D noise at the
    rate it reduces 2D noise; same for viewing full-res images from a distance,
    or printed small; the lines do not fade away, whether they are perceived as
    lines or not.

    I've taken blackframes from my Canons and binned them down to ridiculous
    levels, and all that remains is horizontal and vertical lines with no 2D
    random noise left; the bands are resilient.

    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    John Sheehy, Mar 9, 2007
    #65
  6. David J. Littleboy wrote:
    > "Paul Rubin" <http://> wrote:
    >
    >>"David J. Littleboy" <> writes:
    >>
    >>>I'm not seeing pattern noise in pushed images. Here's a 5D ISO 3200 file
    >>>pushed 3 stops. Straight from Lightroom with noise reduction (and
    >>>sharpening) turned off.
    >>>
    >>>http://www.pbase.com/davidjl/image/75374090/original

    >>
    >>You mean this is at 25,600?

    >
    >
    > Exactly!


    David,
    Pretty cool demonstration.

    Here is pushing some other limits with a Canon 1D Mark II:

    Night and Low Light Photography with Digital Cameras
    http://www.clarkvision.com/photoinfo/night.and.low.light.photography

    Figures 3a, 3b are 623 second exposures at ISO 1600.

    Figure 4, set 2 equivalent to ISO 66,450!
    Figure 4, set 3 is an average of 6 frames at ISO 374,000!

    Figure 5, set 5 is a single frame at ISO 3,883,000 !!!

    Figure 8: night scene at equivalent ISO 16,000.
    Figure 9: night scene at equivalent ISO 64,000 (no dark subtraction).
    Figure 12: night scene at equivalent ISO320,000 (with dark subtraction).

    Figure 13: night scene: 64 frames averaged at ISO 320,000.

    Try that with film: you would get nothing.

    For Ray:
    Electronic sensors have quantum efficiencies in the
    30% range, and film a percent or so, so right there, one
    sees that electronic sensors are much more sensitive.
    Next combine the fact that there is a threshold with film
    requiring a fair number of photons before a grain will
    record the light, then add the fact of reciprocity failure
    and there are significant technical reasons why film does not do
    well in low light situations.

    Add the above facts and it is no wonder why amateur astronomers
    had pretty much abandoned film for digital cameras.
    Amateur astronomers are getting much better astrophotos
    with DSLRs than they every did with film, even when using
    DSLRs on smaller telescopes in light polluted skies!
    The results are truly astounding. For example:
    a 27-minute exposure from light polluted Denver of the Pleiades:
    http://www.clarkvision.com/gallerie...eb/m45-700MM-8534-8561_C16B-add27-v3-800.html
    is better than I ever did with the best long exposure professional
    astronomical film (103aF) from dark skies and longer exposures
    with faster lenses.

    Action: DSLRs produce better images at high ISO than any film
    I ever used. E.g., here is a lion eating a zebra before
    sunrise on the Serengeti a few weeks ago (1/250 sec at ISO 800):
    http://www.clarkvision.com/galleries/gallery.africa/web/lion.c01.23.2007.JZ3F0240b-700.html
    I couldn't have gotten much of an image with film pushed
    to ISO 800. Other examples are on my web site.

    Roger
     
    Roger N. Clark (change username to rnclark), Mar 9, 2007
    #66
  7. ipy2006

    Paul Rubin Guest

    "Roger N. Clark (change username to rnclark)" <> writes:
    > Here is pushing some other limits with a Canon 1D Mark II:
    >
    > Night and Low Light Photography with Digital Cameras
    > http://www.clarkvision.com/photoinfo/night.and.low.light.photography


    Wow, neat. The super-high-ISO examples have very visible horizontal
    banding--what happens if you take that out with a notch filter?

    Is there a feasible way to remove the Bayer filter from a DSLR sensor?

    What about shorter exposures at super ISO's?
     
    Paul Rubin, Mar 9, 2007
    #67
  8. John Sheehy wrote:

    > Paul Rubin <http://> wrote in
    > news::
    >
    >>I don't see how the 1Dmk3 does better given the various observations
    >>that the 20D's low light performance is limited basically by photon
    >>noise.

    >
    > It is a widely held belief that current cameras are limited mainly by
    > photon noise, and Roger Clark's work is often quoted and referenced to
    > support it, but I, for one, don't believe it. I believe that photon noise
    > is a relatively pleasant-looking noise, and it is ruined by patterned read
    > noises (both blackframe offset, and scalar illumination noises), which have
    > much more visual power than the randomly-distibuted poisson shot noise.


    Photon noise has a unique signature: it follows a square root dependence
    on signal strength. You may not believe my results, but then how do you
    explain all the other testing from the sensor manufacturers, university
    testing, and other amateur astronomers testing that come to the
    same conclusion and get the same results?
    What noise source would you advocate that shows a square root dependence?
    Why would the expected photon noise agree with derived quantum
    efficiencies that agree with published QE levels?

    Sure at the very low end, read noise, A/D quantization and pattern noise
    is present, and that is also shown in the online test reports, but that
    is usually below the level most people work at, and it is also
    easily calibrated out for those who want to work at the lower levels
    (e.g. astrophotographers. The implications of the 1D Mark III specs
    imply significant improvements in this area too.

    > That said, Canon does claim less wasted space on the sensor (higher fill
    > factor) over the mkII, and greater quantum efficiency,


    I didn't see any claim in increased quantum efficiency.
    Efficiency due to fill factor and micro-lens improvements perhaps,
    but not device quantum efficiency (although I would be happy
    if I'm wrong here).

    For those just joining, some relevant references on the subject:
    http://www.clarkvision.com/imagedetail/index.html#sensor_analysis

    Summary of data from many sources and also many references:
    http://www.clarkvision.com/imagedetail/digital.sensor.performance.summary

    Roger
     
    Roger N. Clark (change username to rnclark), Mar 9, 2007
    #68
  9. ipy2006

    ASAAR Guest

    On 08 Mar 2007 19:26:39 -0800, Paul Rubin
    <http://> wrote:

    > Is there a feasible way to remove the Bayer filter from a DSLR sensor?


    Would the Kodak DCS Pro 14n do? In a post from last July, a
    Bystander giveth thusly:

    > The 14 megapixel images it produces contain appreciably more
    > information, as expressed in detail, colour, brightness range and so on
    > than the old Kodachrome 25 slides in my library that I produced with the
    > same lenses. They will reproduce excellently on A4 glossy magazine stock
    > with as fine a screen lpi as you want.


    but in concluding, all too quickly taketh away:

    > My main anxiety about the Pro 14n, incidentally, is whether or not the
    > batteries for it will still be available for the life of the camera. Use
    > it in the right circumstances and the results are great -- but issues
    > like slow startup, horrid noise levels in low light and surprising moire
    > effects -- you wouldn't get that with Kodachrome -- easily justify the
    > camera's discontinuance.
     
    ASAAR, Mar 9, 2007
    #69
  10. ipy2006

    Paul Furman Guest

    ASAAR wrote:

    > Paul Rubin wrote:
    >
    >>Is there a feasible way to remove the Bayer filter from a DSLR sensor?


    As in B&W?


    > Would the Kodak DCS Pro 14n do? In a post from last July, a
    > Bystander giveth thusly:


    Is this monocrome?

    >>The 14 megapixel images it produces contain appreciably more
    >>information, as expressed in detail, colour, brightness range and so on
    >>than the old Kodachrome 25 slides in my library that I produced with the
    >>same lenses. They will reproduce excellently on A4 glossy magazine stock
    >>with as fine a screen lpi as you want.

    >
    > but in concluding, all too quickly taketh away:
    >
    >>My main anxiety about the Pro 14n, incidentally, is whether or not the
    >>batteries for it will still be available for the life of the camera. Use
    >>it in the right circumstances and the results are great -- but issues
    >>like slow startup, horrid noise levels in low light and surprising moire
    >>effects -- you wouldn't get that with Kodachrome -- easily justify the
    >>camera's discontinuance.
     
    Paul Furman, Mar 9, 2007
    #70
  11. ipy2006

    ASAAR Guest

    On Fri, 09 Mar 2007 06:53:49 GMT, Paul Furman wrote:

    >> Would the Kodak DCS Pro 14n do? In a post from last July, a
    >> Bystander giveth thusly:

    >
    > Is this monocrome?


    Monochrome?? The Kodak DSLRs (IIRC) did away with the AA filters,
    which allowed them to produce very sharp images, but which had
    negative side effects, such as a tendency to produce more noticeable
    moire, and some "stair step" artifacts by straight edges. There was
    also a version of the Kodak that used a Canon body, the last one
    being made by Sigma when Canon declined further participation. I
    don't know if the Sigma version was or wasn't sold, just having read
    about it in an article that was an extended "hands on" review of the
    Nikon body version which had been used by the reviewer for several
    months.


    >>>The 14 megapixel images it produces contain appreciably
    >>> more information, as expressed in detail, colour, . . .


    Nope, not monochrome. :)
     
    ASAAR, Mar 9, 2007
    #71
  12. ipy2006

    nospam Guest

    In article <>, ASAAR
    <> wrote:

    > There was
    > also a version of the Kodak that used a Canon body, the last one
    > being made by Sigma when Canon declined further participation. I
    > don't know if the Sigma version was or wasn't sold, just having read
    > about it in an article that was an extended "hands on" review of the
    > Nikon body version which had been used by the reviewer for several
    > months.


    i saw someone using one about a year ago, so they've sold at least one.
     
    nospam, Mar 9, 2007
    #72
  13. ipy2006

    acl Guest

    On Mar 9, 6:11 am, John Sheehy <> wrote:
    > "acl" <> wrote innews::
    >
    > > Where did you see this horizontal banding?

    >
    > It was not readily visible in the D200, for the reason I mentioned. The
    > ratio of 2D noise to 1D noise determines how well you can see the 1D noise.


    Well yes, but i can clearly see vertical bands and cannot see
    horizontal bands at all (and not the high-contrast business, it's
    patterned noise).
    > I extracted the 1D components from the image, from an unilluminated area,
    > and the intensity was actually greater than with my Canon 20D, which has a
    > reputation for banding at high ISOs. I subsequently did the same for
    > several cameras by various manufacturers, and found that they all had
    > banding, and all had stronger banding than the 20D, but their 2D random
    > noise was so much more so that the banding was masked.


    Well ok I'll look again. I will be surprised if there's are horizontal
    banding and I've misses it, but it could be there.

    > By banding, I mean offsets in the RAW data on a line-by-line basis, visible
    > or not. Even when banding is not visible as "banding", it's removal still
    > makes the remaining noise look much more natural (except, of course, for
    > the inherent pixel grid of both the signal and noise), despite the fact
    > that the standard deviation may drop by less than 1%. Any patterned or 1D
    > noise, is much more destructive per unit of standard deviation, than 2D
    > random noise. Even binning and downsampling fail to reduce 1D noise at the
    > rate it reduces 2D noise; same for viewing full-res images from a distance,
    > or printed small; the lines do not fade away, whether they are perceived as
    > lines or not.


    Yes, I've noticed the same thing.
     
    acl, Mar 9, 2007
    #73
  14. Paul Rubin wrote:
    > "Roger N. Clark (change username to rnclark)" <> writes:
    >> Here is pushing some other limits with a Canon 1D Mark II:
    >>
    >> Night and Low Light Photography with Digital Cameras
    >> http://www.clarkvision.com/photoinfo/night.and.low.light.photography

    >
    > Wow, neat. The super-high-ISO examples have very visible horizontal
    > banding--what happens if you take that out with a notch filter?


    I have not tried that.

    But all this talk about banding is a little
    mis-informed in my opinion. John Sheehy seems to be saying that
    because there is banding obvious at the low end is evidence for
    non-photon noise sources. While true, one must look at the
    level of the banding. For example, examine Figure 5 on the above web
    page. Set 5 in Figure 5 shows banding at a similar level as the signal
    in panels A and B (the left most two squares). But look at the table:
    the photons per pixel is only 1.2 in panel A and 0.8 in panel B!
    The read noise is 3.9 electrons, so the pattern noise is
    about 1/4 the read noise. The problem is that our eyes plus
    brain are very good at picking out patterns, whether that pattern
    is below random noise, or embedded in other patterns.

    It would be interesting to try some filtering on the images.

    > Is there a feasible way to remove the Bayer filter from a DSLR sensor?


    I do not know.

    > What about shorter exposures at super ISO's?


    Figure 12 on the above web page is a 1/20 second exposure at equivalent
    ISO = 320,000. Do you want faster than that? It is simply a matter of photons
    per pixel per exposure. I would not think faster exposures with
    similar photons/pixel would appear any different. Longer at lower
    light levels would not appear any different either until noise from
    dark current starts to show. Dark current noise is the square root
    of the dark current, and the 1D Mark II under the temperatures used
    was around 0.03 electron/second. So a 10 second exposure would
    about a 0.5 electron noise to the 3.9 electron read noise. Thermal
    noise equals read noise after about 5 minutes.

    Roger
     
    Roger N. Clark (change username to rnclark), Mar 9, 2007
    #74
  15. ipy2006

    acl Guest

    On Mar 9, 2:28 pm, "Roger N. Clark (change username to rnclark)"
    <> wrote:
    > Paul Rubin wrote:
    > > "Roger N. Clark (change username to rnclark)" <> writes:
    > >> Here is pushing some other limits with a Canon 1D Mark II:

    >
    > >> Night and Low Light Photography with Digital Cameras
    > >> http://www.clarkvision.com/photoinfo/night.and.low.light.photography

    >
    > > Wow, neat. The super-high-ISO examples have very visible horizontal
    > > banding--what happens if you take that out with a notch filter?

    >
    > I have not tried that.
    >
    > But all this talk about banding is a little
    > mis-informed in my opinion. John Sheehy seems to be saying that
    > because there is banding obvious at the low end is evidence for
    > non-photon noise sources. While true, one must look at the
    > level of the banding. For example, examine Figure 5 on the above web
    > page. Set 5 in Figure 5 shows banding at a similar level as the signal
    > in panels A and B (the left most two squares). But look at the table:
    > the photons per pixel is only 1.2 in panel A and 0.8 in panel B!
    > The read noise is 3.9 electrons, so the pattern noise is
    > about 1/4 the read noise. The problem is that our eyes plus
    > brain are very good at picking out patterns, whether that pattern
    > is below random noise, or embedded in other patterns.
    >


    Actually I read his posts as saying, not that photon shot noise is
    less important than you say in absolute terms, but that he finds
    banding more disturbing. It seems to be a perceptual judgement; he
    doesn't appear to be claiming anything quantitatively different from
    what you say, just that it bothers him.

    For what it's worth, I personally also find patterned noise much more
    disturbing than random noise (I really don't mind random noise all
    that much unless it gets to very high levels; of course it complicates
    my postprocessing but that is another story). It also seems to be the
    case that this patterned noise is more obvious to some people than to
    others: I have prints from pushed high isos which I find have very
    disturbing patterned noise (it jumps out at me immediately, and is
    perceptually almost as strong as the image), while my wife and a
    couple of friends don't notice it until I point it out, and then seem
    to be unaware of it unless they consciously decide to "see" it. I
    can't avoid seeing it at all. It seems to depend on the person; maybe
    this is part of this confusion (or maybe not).
     
    acl, Mar 9, 2007
    #75
  16. acl wrote:
    >
    > Actually I read his posts as saying, not that photon shot noise is
    > less important than you say in absolute terms, but that he finds
    > banding more disturbing. It seems to be a perceptual judgement; he
    > doesn't appear to be claiming anything quantitatively different from
    > what you say, just that it bothers him.
    >
    > For what it's worth, I personally also find patterned noise much more
    > disturbing than random noise (I really don't mind random noise all
    > that much unless it gets to very high levels; of course it complicates
    > my postprocessing but that is another story).


    I too agree that pattern noise is more obvious that random noise.
    Probably by at least a factor of ten. It is our eye+brain's
    ability to pick out a pattern in the presence of a lot
    of random noise that makes us able to detect many things
    in everyday life. It probably developed as a necessary
    thing for survival. But then it becomes a problem when we try
    and make something artificial and we see the defects in it.
    It gives the makers of camera gear quite a challenge.

    Roger
     
    Roger N. Clark (change username to rnclark), Mar 10, 2007
    #76
  17. ipy2006

    John Sheehy Guest

    "Roger N. Clark (change username to rnclark)" <> wrote
    in news::


    > But all this talk about banding is a little
    > mis-informed in my opinion. John Sheehy seems to be saying that
    > because there is banding obvious at the low end is evidence for
    > non-photon noise sources. While true, one must look at the
    > level of the banding. For example, examine Figure 5 on the above web
    > page. Set 5 in Figure 5 shows banding at a similar level as the
    > signal in panels A and B (the left most two squares). But look at the
    > table: the photons per pixel is only 1.2 in panel A and 0.8 in panel
    > B! The read noise is 3.9 electrons, so the pattern noise is
    > about 1/4 the read noise. The problem is that our eyes plus
    > brain are very good at picking out patterns, whether that pattern
    > is below random noise, or embedded in other patterns.


    Yes, that is a problem, and that is exactly why you can't evaluate noise by
    standard deviation alone. It doesn't even take human perception to focus
    on the banding; binning and downsampling math focus on it too; an
    blackframe from a 20D with 10x the total noise as the horizontal banding
    component will show *only* banding noise, and no visible 2D noise at all,
    if binned down far enough. I think that this fact speaks volumes as to how
    useless standard deviations and S/N ratios based on them can be when
    comparing different *characteristics* of noises.


    > Thermal noise equals read noise after about 5 minutes.


    Statistically, perhaps, but standard deviation does not tell the full
    story. You can clearly compare the standard deviations of two noise
    situations with the same characteristics, which only vary in terms of
    amplitude, but noise comes in a variety of characteristics, and the
    standard deviations are not necessarily related to the visual strength of
    noise when the characteristics are different. Dark current noise is much
    more visible than shot noise, with the same standard deviation, because
    most of its energy goes into a minority of pixels.


    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    John Sheehy, Mar 11, 2007
    #77
  18. ipy2006

    John Sheehy Guest

    "Roger N. Clark (change username to rnclark)" <> wrote in
    news::

    > I too agree that pattern noise is more obvious that random noise.
    > Probably by at least a factor of ten. It is our eye+brain's
    > ability to pick out a pattern in the presence of a lot
    > of random noise that makes us able to detect many things
    > in everyday life. It probably developed as a necessary
    > thing for survival. But then it becomes a problem when we try
    > and make something artificial and we see the defects in it.
    > It gives the makers of camera gear quite a challenge.


    How does that co-exist with your conclusion that current cameras are
    limited by shot noise?

    Saying that current cameras are limited by shot noise means that all future
    improvements lie purely in well depth, quantum efficiency, fill factor, and
    sensor size (you'd probably add "large pixels", but I'd disagree). The
    fact is, a 10:1 S:N on the 1DmkII at ISO 100 would be 1.5 stops further
    below saturation, and 1:1 would be 4.3 stop further below it, if there were
    no blackframe read noise

    http://www.pbase.com/jps_photo/image/75392571

    and that is only statistically, without consideration for the pattern noise
    effects, which widen the visual gap even further.

    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    John Sheehy, Mar 11, 2007
    #78
  19. "John Sheehy" <> wrote in message
    news:Xns98F06D6F99D10jpsnokomm@130.81.64.196...
    > "Roger N. Clark (change username to rnclark)" <>
    > wrote
    > in news::
    >
    >
    >> The problem is that our eyes plus brain are very good at
    >> picking out patterns, whether that pattern is below random
    >> noise, or embedded in other patterns.


    What's worse, we see non-existing patterns (e.g. a triangle in the
    following link) because we want to:
    <http://www.xs4all.nl/~bvdwolf/temp/Triangle-or-not.gif>.

    > Yes, that is a problem, and that is exactly why you can't evaluate
    > noise by standard deviation alone.


    That depends what one wants to evaluate. Standard deviation (together
    with mean) only tells something about pixel to pixel (or sensel to
    sensel) performance. It doesn't allow to make valid judgements about
    anything larger. Banding could be either calibrated out of the larger
    structure, or an analysis of systematic noise should be done (and care
    should be taken to not mistake Raw-converter effects for camera or
    sensor array effects).

    --
    Bart
     
    Bart van der Wolf, Mar 11, 2007
    #79
  20. "John Sheehy" <> wrote in message
    news:Xns98F06DCDB2811jpsnokomm@130.81.64.196...
    > "Roger N. Clark (change username to rnclark)" <>
    > wrote in
    > news::
    >
    >> I too agree that pattern noise is more obvious that random noise.
    >> Probably by at least a factor of ten. It is our eye+brain's
    >> ability to pick out a pattern in the presence of a lot
    >> of random noise that makes us able to detect many things
    >> in everyday life. It probably developed as a necessary
    >> thing for survival. But then it becomes a problem when we try
    >> and make something artificial and we see the defects in it.
    >> It gives the makers of camera gear quite a challenge.

    >
    > How does that co-exist with your conclusion that current cameras are
    > limited by shot noise?


    Shot noise is a physical limitation, not a man made one. The man made
    limitations can be improved upon.

    --
    Bart
     
    Bart van der Wolf, Mar 11, 2007
    #80
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