Foveon technology

Discussion in 'Digital Photography' started by John McGraw, Aug 3, 2004.

  1. John McGraw

    John McGraw Guest

    Hi All
    First, disclaimers:
    #1.) I really don't want to start a flame war, but I have little idea
    how or where else to ask this.
    #2.) Please, please ignore that poor kid, mental case's posts. The one
    who takes famous aviators names. Really the only sensible thing is to
    ignore him. He deserves help, but this is not the forum for it.

    I want to buy my 1st digital camera. I was favoring the Coolpix 5000.
    Liked it's 28 to ~80mm (35mm equiv range). (I believe that anything
    over ~100mm in a non-SLR is absurd. Why did Leica go to a reflex
    housing ~60 yrs ago? Anyway, I digress). And 28mm is a focal length I
    use a lot. 35mm (equiv to 35mm) just doesn't cut it for me. However
    after reading Amazons customer reviews of both the Coolpix 5000 &
    5400, I get the distinct impression Nikon has serious Quality Control
    & design problems w/ those two.
    Then I read a supposedly unbiased review of the Foveon technology,
    claiming that it is truly a significant advancement. "Wiley Post's"
    insanity tends to dissuade me. Can anyone direct me to unbiased
    sources evaluating, testing Foveon technology? I can't get any Amazon
    customer reviews today. Don't know if it's my browser or Amazon's
    problem.
    Of course I realize that there is much more to a camera system than
    just the digitizer.... imiagizer ...uhg ...uhg whatever the f....
    that thing in the back is called, where the film used to be. I
    wouldn't base my decision on that part alone. What is that thing
    called? Focal plane? Light sensors... the pixelator in the back. I've
    been pixilated in the back of some bars in Alaska a few times, but
    that's a different story. Seriously though folks, what is a good, up
    to date digital photography dictionary or computer dictionary that
    covers photo.? I need help in more ways than one.

    Thank You Very Much, John
     
    John McGraw, Aug 3, 2004
    #1
    1. Advertising

  2. In article <>,
    says...
    > I want to buy my 1st digital camera. I was favoring the Coolpix 5000.
    > Liked it's 28 to ~80mm (35mm equiv range). (I believe that anything
    > over ~100mm in a non-SLR is absurd. Why did Leica go to a reflex
    > housing ~60 yrs ago? Anyway, I digress). And 28mm is a focal length I
    > use a lot. 35mm (equiv to 35mm) just doesn't cut it for me. However
    > after reading Amazons customer reviews of both the Coolpix 5000 &
    > 5400, I get the distinct impression Nikon has serious Quality Control
    > & design problems w/ those two.


    Nikon is normally pretty good with quality, and if not quality, customer
    service. I wouldn't worry too much. People can bitch too much.

    > Then I read a supposedly unbiased review of the Foveon technology,
    > claiming that it is truly a significant advancement. "Wiley Post's"
    > insanity tends to dissuade me. Can anyone direct me to unbiased
    > sources evaluating, testing Foveon technology? I can't get any Amazon
    > customer reviews today. Don't know if it's my browser or Amazon's
    > problem.


    http://nordicgroup.us/sigma/

    In my opinion, the Foveon sensor looks good on paper, but it doesn't
    deliver enough for the bux. If you're looking to spend money on a dSLR,
    a Canon dRebel or Nikon D70 will do you just fine. Heck, a lot of 4-5
    megapixel point and shoots can outdo the Foveon in the SD10.

    In case you haven't found it yet:

    http://www.dpreview.com/

    Great site for comparative reviews, sample shots and more.
    --
    http://www.pbase.com/bcbaird/
     
    Brian C. Baird, Aug 3, 2004
    #2
    1. Advertising

  3. John McGraw wrote:
    []
    > I want to buy my 1st digital camera. I was favoring the Coolpix 5000.
    > Liked it's 28 to ~80mm


    Go for it! An excellent camera particularly if the wide-angle end is your
    preference. The 5400 is a more modern alternative. You will learn a lot,
    and then have a better base from which to make any further decisions.

    Cheers,
    David
     
    David J Taylor, Aug 3, 2004
    #3
  4. (John McGraw) wrote in
    news::

    > Then I read a supposedly unbiased review of the Foveon technology,
    > claiming that it is truly a significant advancement. "Wiley Post's"
    > insanity tends to dissuade me. Can anyone direct me to unbiased
    > sources evaluating, testing Foveon technology? I can't get any Amazon
    > customer reviews today. Don't know if it's my browser or Amazon's
    > problem.


    There are two good reviews at www.dpreview.com of SD9 and SD10.
    As with any serious review you can read whatever you like, so
    .... be prepared to see both sides using those reviews in their
    arguments :)

    > Of course I realize that there is much more to a camera system than
    > just the digitizer.... imiagizer ...uhg ...uhg whatever the f....
    > that thing in the back is called, where the film used to be. I
    > wouldn't base my decision on that part alone.


    Yepp ... this is very important to understand. If the Sigma camera
    contained a normal Bayer sensor, there is nothing that recommends it.
    It is more expensive (than Canon 300D and Nikon D70), it has a smaller
    sensor with fewer pixels and you can only use Sigma lenses.

    So ... if you shall buy the Sigma, it is *only* the sensor technology
    that is the reason for doing so. So, if you want to buy a Sigma, make
    sure you like the output from the camera first.


    /Roland
     
    Roland Karlsson, Aug 3, 2004
    #4
  5. "John McGraw" <> wrote in message
    news:...

    > Then I read a supposedly unbiased review of the Foveon technology,
    > claiming that it is truly a significant advancement.


    Just read the reviews on the two consumer cameras that use a Foveon sensor.

    The idea of three photodetectors per pixel is not new. Foveon's first
    attempt was a good try, but as the reviews show, it still lags the more
    widely used Bayer approach. Actually, Foveon's first attempt was using three
    separate sensors and using a prism to separate colors; this worked pretty
    well.

    The Foveon sensor does work well at lower ISOs, and with very good lighting
    conditions.
     
    Steven M. Scharf, Aug 3, 2004
    #5
  6. (John McGraw) wrote in message news:<>...
    > Can anyone direct me to unbiased
    > sources evaluating, testing Foveon technology? I can't get any Amazon
    > customer reviews today. Don't know if it's my browser or Amazon's
    > problem.



    Here they are. Note, there are no such thing as hexagonal pixels, and
    the SD9 outputs 14MP pics straight out of camera with far less
    interpolation (and zero color interpolation) than the S2 uses at 12MP.
    More pixels is bad, bad, bad, not good, unless optical resolution is
    higher and the S2 has about half the SD9's optical resolution accross
    the board (SD9 has 3.43M RGB triplets vs only 1.5M for the S2 Pro).
    Any image can be upscaled to any number of pixels.


    The best camera I ever used! Period!, December 7, 2003
    Reviewer: Boris Vinnik - See all my reviews


    Well, this camera is something special and I have been compelled write
    this review because of couple of reasons. For the first, here the
    reasons. I read many bad , negative reviews of this camera and in the
    same time all those people who actually used it told how much they
    have being amazed by the picture quality it produces. So I've decided
    to try. The camera's images are not amazed they are stunned. The image
    quality is so high that it left me speechless for the first.
    I'm just wandering about those who left negative reviews about it? The
    CNET review, that named it "mediocre SLR camera" is just a plain lie.
    In my opinion they giving point for those who gives more money, it's
    it. Another interesting "review", I read from Ken Rockwell (really
    gifted photo artist!, no questions!), who reviewed this camera without
    even try it!
    So let start. First of all, it is NOT 3.5M camera. It is AT LEAST 10M
    camera, but megapixels in the traditional meaning just are not
    applicable here. This camera produces NEGATIVES. This negative is
    result of 10M photo elements. In the same time any of 6M cameras has
    HALF OF THEM GREEN and ONLY 25% red and another 25% blue. If we speak
    about "image quality" using this kind of "resolution" , this camera
    produces 14M images. In the same time the "real" resolution of those
    "6M" cameras stand about 1.5M, the everything else is a pure deceiving
    interpolation. I see that Cannon and NIkon, aren't happy to see this
    Sigma on the market, since it MUCH SUPERIOR to any camera they make
    they started to discredit it.
    I do not say it is an ideal, but it close. Much closer than everything
    else that feels like SLR.
    This Sigma produces PHOTOGRAPHIC IMAGES. I mean it. There's full range
    of amazing continuos beautiful halftones as you can see on the best
    reversible films. The pictures are spectacular.
    Since it is real photographic tool, you come back to the true that
    photography and it is about light. Your raw pictures will normally
    produce 3000 by 4500 huge images that is not interpolating, they just
    "enlargements" from digital negative. It reviles as many details that
    ANY other camera can't produce. There are 14M cameras on the market,
    but they DO NOT MUCH this SIgma in the meaning of photography. I can
    blow my raw image 4 times more and it still looking better than those
    from 14M Canon. By the way, those image from Cannon show horrible
    color reproduction, especially in the red. For example two closely
    colored redish colors coming out the same!
    This Sigma saves colors! It saves the real colors, not the
    estimations, not the interpolations but the real thing. Camera has
    just the everything that it has to have, including the high speed
    synchronization up to 1/6000 !!!
    The lens from Sigma just as good(or better) as any other lenses from
    Nikon , Cannon or Minolta. Even cheap $100 tag slow glass is of very
    good optical quality. Yes/ for $100 you're getting slow lenses, but it
    almost distortion free and high contrast! But fro $300 you can get
    perfectly fast, noticeably bright zoom that at least as good as any
    lens from "leading companies".
    Camera is very well constructed, it handles as it should be, the
    focusing system is fast, the screen is bright and clear, all controls
    location are very clever and logical. I like this camera and you're
    going to like it too. No boundaries anymore. You can print image as
    large as you need, no questions. In two, three years Foveon will
    overcome. I



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    4 of 4 people found the following review helpful:

    The best image quality currently available at any price, July 12,
    2003
    Reviewer: An electronics fan

    Given reasonable light, this DSLR bests all others in overall image
    quality with its 10.2M sensors and astounding sharpness. The best
    digital portrait camera in existence.

    Don't be fooled by the camera's 3.5MP rating--that is
    non-interpolated--all other digital camera manufactures, including all
    DSLRs, list only interpolated resolutions as their MP rating. This
    inflates other cameras' MP rating by a factor of 3 times relative to
    the SD-9, since they count each Red, Green, and Blue sensor as a sigle
    "pixel." The SD-9 counts a full set of three sensors, one Red, one
    Green, and one Blue, as a single "pixel." Foveon.com claims the SD-9's
    image quality bests film for any given capture area, and approaches
    medium format film quality for enlargements up to 40 inches. Some
    report that sharp enlargements up to 8 feet on the long side are
    possible from the SD-9's interpolated 14MP output files. The camera's
    software is the best available. The SD-9 always works losslessly, so
    be sure to compare only RAW mode specs when comparing to other DSLR's
    operating speed and convenience of workflow.

    Price is amazingly low for a DSLR with so many sensors, now below
    [$$$]...Hopefully Amazon.com will match them soon.

    Not the best DSLR for low light--low light noise is a weakness. Still,
    can produce very fine low light/night pics with experience.



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    14 of 19 people found the following review helpful:

    Great pictures, hefty price, May 9, 2003
    Reviewer: An electronics fan (Edmond, Oklahoma)

    I'm basically a point and shoot kinda guy. Before this I owned a run
    of the mill Olympus D-490.
    Wow, what a difference. I've been snapping away for over 2 weeks with
    this little gem and am shocked at the picture quality. It's amazing
    what a little jump in technology can do. This X3 chip produces great
    color, fantastic detail and it's easy enough to have running in
    minutes, providing you have all the batteries, and it takes alot.

    The downsides are that it's heavy, like a couple of pounds w/ the lens
    and flash (sold separately). It's expensive, try shelling out 1.5k USD
    and telling your wife it's for a camera. Ouch.
    It requires Sigma software - I think if your going to charge an arm
    and a leg for a camera, it should take images in a standardized
    format. I appreciate the fact that the images in "sigma" format are
    infinitely manipulatable, but geesh. At least give us a choice if we
    want all that control in every shot.
    The pics cant be blown up very much. Now as an aside, I'm no master
    with the software yet, but on Hi quality with autofocus on the darn
    thing makes great pics, but viewing at anything over 2:1 magnification
    in Paint Shop produces pixelated images. It's a quirk, but it matters
    to me.

    Other than that, like I said, images are great. It's fun to run
    because it's so much like a pro-shot camera, but still easy enough for
    the average PHD to run it. (PHD= Push Here Dummy ;)

    This camera is great.., December 27, 2002
    Reviewer: "webcamdotcom" (Irvine, CA USA) - See all my reviews
    I got mine last week, and it's image quality is the best of any
    digital camera.
    My only complaint is that for the price they skimped on the little
    things... Specifically one of the battery doors is poorly made (I
    broke it after inserting the batteries :-( )

    But after shooting pictures almost continuously over the holidays, I
    have to say that the Sony 717 doesn't compare.

    Lance

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    35 of 39 people found the following review helpful:

    the future of digital, November 22, 2002
    Reviewer: "shentzu" (AZ) - See all my reviews
    unlike some reviewers, i have actually seen and held this camera.
    while i only took 3 pictures, simply loading them and having a look is
    shocking. this camera and the underlying X3 chip blow away everything
    in digital photography today. getting all three colors (rather than
    one like all other digital cameras) in each pixel gives you images you
    can easily enlarge without loss and artifacts. this camera easily
    blows away cameras costing many times more.
    this isn't a true 3 MP camera. it is more like a 9 MP. but better....
    there is no longer a reason to not go digital.

    getting 3 colors per pixel means no interpolation. that in turn means
    sharper, truer color, photos without artifacts. in short, digital
    photos without the digital look. some of the photos taken with this
    camera are as good as medium format film images.

    digital is not as good as film, it is now better.

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    11 of 24 people found the following review helpful:

    has anyone tried this camera?, November 11, 2002
    Reviewer: A customer
    My star rating doesn't count because I have not tried the product.
    Seattle customer, is it correct to infer that your opinion is not
    based on actually trying the camera? As I understand it, the Foveon
    image sensor in the SD9 is different from the sensors in the 6
    megapixel cameras you refer to in that each pixel in the SD9 is
    capable of sensing either red, blue, or green light, whereas in the
    conventional sensors any given pixel can only sense one color. That
    means it takes three pixels in a conventional sensor to provide the
    true color data provided by one pixel in the Foveon sensor. There may
    be more pixels in an image from a 6 mp sensor, but many of those
    pixels are artificially created by computer interpolation rather than
    being based on direct sensing of incoming light. Also this means the
    conventional camera must take more time to process the image in
    camera.

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    28 of 102 people found the following review helpful:

    Good start by Sigma, but probably better to wait, April 26, 2002
    Reviewer: "alan_james" (Wickwar, South Glos England) - See all my
    reviews
    The Sigma uses a new kind of light collecting chip which senses R,B,G
    colours at each of the 3.4 million pixels on its chip. The more common
    chip used by all other cameras senses only one colour at each pixel.
    So the Sigma should win hands down! Not necessarily. 3.4Mp isn't many
    pixels. Sony, Nikon et al. have 6Mp cameras using the standard type
    sensor. At the end of the day, more pixels give better resolution. So
    a 6Mp sensor does as well as the Sigma 3Mp sensor for colour and
    resolution.
    Fuji has tweaked the standard sensor format to use hexagonal pixels
    and get better resolution out of their 6Mp sensor chip. In August 2002
    the Fuji S2 pro is due out, and its 6Mp chip will produce 12Mp photos.
    That's 12 million pixels of info to make a photo. They do this by
    analysing the data from the 6Mp and modifying it to "fill in" extra
    detail and colour. The result to Joe bloggs on the street will be
    photos pretty close to ordinary 35mm quality.

    If Sigma produce a camera using their new technology chip but with
    6Mp, then it will be a force to reckon with.

    Slight problems with Sigma are you have to use their lenses. The Fuji
    is made to use Nikon lenses. Canon and Nikon have their own
    equivalents to the Fuji.

    Personally I'm waiting for the Fuji S2 Pro as I already have a Nikor
    AF auto-focus lens which I'm not ready to pass up. The Fuji is going
    to cost less than its Canon/Nikon counterparts...

    Was this review helpful to you? (Report this)
     
    Georgette Preddy, Aug 3, 2004
    #6
  7. Yawn...
     
    Randall Ainsworth, Aug 3, 2004
    #7
  8. (Georgette Preddy) writes:

    >Here they are. Note, there are no such thing as hexagonal pixels, and
    >the SD9 outputs 14MP pics straight out of camera with far less
    >interpolation (and zero color interpolation) than the S2 uses at 12MP.
    > More pixels is bad, bad, bad, not good, unless optical resolution is
    >higher and the S2 has about half the SD9's optical resolution accross
    >the board (SD9 has 3.43M RGB triplets vs only 1.5M for the S2 Pro).
    >Any image can be upscaled to any number of pixels.


    An amazing number of misleading statements for one paragraph. In actual
    fact:

    The SD9/SD10 have 3.4 million sensor pixels, lower than any other
    current DSLR. Each pixel has 3 colour sensors, for a total of 10.2
    million photosensors (a number you'll also see in reviews), but there
    are only 3.4 million spatially-separate sensing locations and that's
    what determines the ability to resolve fine detail. Competing DSLRs
    have 6 million or more measuring locations. The Sigma raw processing
    software can produce 14 MP images using interpolation, but this process
    adds no useful detail at all.

    Other cameras use Bayer sensors that measure only one colour per pixel
    but despite that yield the same resolution as a Foveon or B&W sensor
    with the same pixel count. Georgette's references to counting 4 pixels
    as "RGB triplets" or dividing pixel count by 4 to get "optical
    resolution" are complete fabrications, with no basis.

    Standard resolution tests show that the Sigma cameras have lower
    resolution than any of the other current DSLRs. This is true measured
    "optical resolution", not what Georgette uses the same term for.

    The Sigma cameras do not use an anti-aliasing filter in the camera.
    This gives images that *look* sharper than other 3.4 MP cameras, but at
    the expense of inaccurate rendering of diagonal edges and thin lines,
    and sometimes moire effects. Some people like the effect, some do not.

    The one advantage that the Sigma cameras *should* get from measuring 3
    colours at every pixel is higher-resolution colour than a Bayer sensor.
    However in practice the technology so far has a reputation for
    inaccurate and blotchy colour rendition with some subjects.

    Now, there *are* people who like the Sigma cameras for the sort of
    subjects they shoot. If you search the archives for this group in
    Google, you'll find them. Just don't believe anything
    "George/Georgette" writes. This person has been demonstrated to
    misrepresent the results of tests, edit the text of other people he's
    quoting to apparently support his position when they do not, and make up
    explanations out of thin air.

    Dave
     
    Dave Martindale, Aug 3, 2004
    #8
  9. In article <>, John
    McGraw <> writes
    >Hi All
    >First, disclaimers:
    >#1.) I really don't want to start a flame war, but I have little idea
    >how or where else to ask this.
    >#2.) Please, please ignore that poor kid, mental case's posts. The one
    >who takes famous aviators names. Really the only sensible thing is to
    >ignore him. He deserves help, but this is not the forum for it.
    >
    >I want to buy my 1st digital camera. I was favoring the Coolpix 5000.
    >Liked it's 28 to ~80mm (35mm equiv range). (I believe that anything
    >over ~100mm in a non-SLR is absurd. Why did Leica go to a reflex
    >housing ~60 yrs ago? Anyway, I digress). And 28mm is a focal length I
    >use a lot. 35mm (equiv to 35mm) just doesn't cut it for me. However
    >after reading Amazons customer reviews of both the Coolpix 5000 &
    >5400, I get the distinct impression Nikon has serious Quality Control
    >& design problems w/ those two.
    >Then I read a supposedly unbiased review of the Foveon technology,
    >claiming that it is truly a significant advancement. "Wiley Post's"
    >insanity tends to dissuade me. Can anyone direct me to unbiased
    >sources evaluating, testing Foveon technology? I can't get any Amazon
    >customer reviews today. Don't know if it's my browser or Amazon's
    >problem.
    >Of course I realize that there is much more to a camera system than
    >just the digitizer.... imiagizer ...uhg ...uhg whatever the f....
    >that thing in the back is called, where the film used to be. I
    >wouldn't base my decision on that part alone. What is that thing
    >called? Focal plane? Light sensors... the pixelator in the back. I've
    >been pixilated in the back of some bars in Alaska a few times, but
    >that's a different story. Seriously though folks, what is a good, up
    >to date digital photography dictionary or computer dictionary that
    >covers photo.? I need help in more ways than one.
    >
    >Thank You Very Much, John


    I agree with the commonly held view that you should ignore anything that
    Preddy-Stupid says; the man has a screw loose.

    However, it is fair to point out that some well-respected commentators
    have had good things to say about the Sigma DSLRs. You could try looking
    (on Google) for a couple of posts by David Kilpatrick. David is a
    magazine publisher in the UK, and from my knowledge of him (I have been
    a subscriber for many years) he has a lot of experience and gives a good
    balanced opinion.

    I personally would not, despite his view, buy a Sigma camera. They have
    dented any faith I may have had by a couple of bad experiences with
    their lenses, and the negative factors do seem too much to overcome.
    Besides, I already had a fortune invested in Canon lenses, and the Sigma
    bodies only take Sigma lenses.

    The Coolpix series seems pretty good to me - I have a 995, which I use
    mainly for photomicroscopy (for which it is ideal). The lens has a touch
    of barrel distortion IIRC. I regret the change in form-factor Nikon made
    after the 4500 - but that is because the swivel body is ideal for my
    specialist use; I'm sure it is relatively unimportant for normal use.
    --
    David Littlewood
     
    David Littlewood, Aug 4, 2004
    #9
  10. John McGraw

    Mitch Alsup Guest

    (Georgette Preddy) wrote in message news:<>...
    > (John McGraw) wrote in message news:<>...


    > So let start. First of all, it is NOT 3.5M camera. It is AT LEAST 10M
    > camera, but megapixels in the traditional meaning just are not
    > applicable here. This camera produces NEGATIVES. This negative is
    > result of 10M photo elements. In the same time any of 6M cameras has
    > HALF OF THEM GREEN and ONLY 25% red and another 25% blue. If we speak
    > about "image quality" using this kind of "resolution" , this camera
    > produces 14M images. In the same time the "real" resolution of those
    > "6M" cameras stand about 1.5M, the everything else is a pure deceiving
    > interpolation.


    No, not quite. You see, most of the resolution 'information' in a picture
    is carried in the luminance channel. And a 6MP bayer sensor can resolve
    6MPs of luminance information. In mathematical terms, if you have a sensor
    with 3002 horizontal and 2002 vertical sensors, you can derive 3000*2000
    {(h-2)*(v-2)} = 6MP of luminance information.

    The Foveon sensor has only 3 MP of luminance information. Simply because
    the pixels are registered in depth at the same location as opposed to
    being registered in an array with each pixel at a different location!

    Back to bayer: consider the pixels as:
    1234567890
    1 RGRGRGRGRG
    2 GBGBGBGBGB
    3 RGRGRGRGRG
    4 BGBGBGBGBG

    There is an
    RGB pixel at {(1,1),(1,2),(2,2)} Locus (1.66,1.5)
    another at {(1,3),(1,2),(2,2)} Locus (2.66,1.5)
    another at {(1,1),(2,1),(2,2)} Locus (1.5,1.66)

    Notice how moving a single R pixel from (1,1) to (1,3) give a new luminance
    pixel even while the G and B pixels remain the same! This is why the bayer
    sensor structure does not compress to 1.5M pixels of R or B. Because you
    extract information from all compositions of all the tripple RGB sensors.

    Now let us take a look at color. Taking pixel in pairs allows the matrix
    algorythm to extract yellows (RG) purples (RB) and Aquas (GB). In effect
    the bayer matrix solution can extract lots of information from the sensors
    and then composit this information back into RGB or CYMK formats that
    gets stored on the CF.

    Therefore: a bayer sensor array has {(h-2)*(v-2)} actual pixels of
    'information' from and array of {h,v} sensors.

    While a foveon array only has the number of sensor locations it actually
    has (not 3X) of information.

    Mitch
     
    Mitch Alsup, Aug 5, 2004
    #10
  11. Hi Mitch

    This is a lengthy posting for sure

    But surely luninence is measured under the mask?

    How can it be full luminence?

    A very bright red light is not going to create a whopping luminence value in
    photosensors filtered by G and B mask is it?

    Arts


    "Mitch Alsup" <> wrote in message
    news:...
    <snipped>
     
    Arty Phacting, Aug 5, 2004
    #11
  12. John McGraw

    Mitch Alsup Guest

    "Arty Phacting" <> wrote in message news:<PBvQc.571$>...
    > Hi Mitch
    >
    > This is a lengthy posting for sure
    >
    > But surely luninence is measured under the mask?
    >
    > How can it be full luminence?


    Every combination of neighboring RGB pixels can be composited as a
    luminance signal at the centroid of that RGB set of pixels.

    >
    > A very bright red light is not going to create a whopping luminence value in
    > photosensors filtered by G and B mask is it?


    That is correct, a light with a wavelength that does not excite
    electron creation in the storage well does not get 'read' out as
    'illuminating' that pixel (of whatever color). However, the black
    and white version of an RGB tripplet still has a luminance value
    even when the G and B cells are dark.

    What I was trying to indicate is that one does not draw a single
    triangle around a RGB tripplet and call that tripplet a color pixel.
    One draws every possible tripplet (4) around every colored pixel
    and derives 4 pseudo color pixel components from each and every
    RGB-pixel. That is why the observed resolution is equal to the
    total pixel count and not pixel/4 count. All of this is done in
    a coordinate space finer than the diameter of a pixel and then
    gets reduced back into the coordinate space of the RAW output.

    Mitch
     
    Mitch Alsup, Aug 6, 2004
    #12
  13. "Arty Phacting" <> writes:

    >But surely luninence is measured under the mask?


    >How can it be full luminence?


    It's full *resolution* luminance, given normal subject matter.

    >A very bright red light is not going to create a whopping luminence value in
    >photosensors filtered by G and B mask is it?


    What kind of red light? The sort of red light that you see from a red
    bulb, or through a red filter, will contribute some signal in the green
    and blue pixels as well.

    On the other hand, a very pure longwave red like you might get from a
    red laser or LED could produce a usable signal in only the red pixels.
    In that case, the luminance (and colour) will *still* be captured
    correctly if the image contains only patterns with a spatial frequency
    of 0.25 cycles/pixel and lower (half the regular luminance limit).

    Patterns of very pure red at spatial frequencies between 0.25 and 0.5
    cycles/pixel could indeed be misinterpreted by the camera. However, how
    often do you shoot images containing anything like this?

    To cause a problem, the image content needs to be *both* pure in colour,
    of a colour that only one filter will pass, and above 0.25 cycle/pixel
    but below 0.5 cycles/pixel.

    Dave
     
    Dave Martindale, Aug 6, 2004
    #13
  14. John McGraw

    John McGraw Guest

    (Dave Martindale) wrote in message news:<ceodgp$dvp$>...
    > (Georgette Preddy) writes:
    >
    > >Here they are. Note, there are no such thing as hexagonal pixels, and
    > >the SD9 outputs 14MP pics straight out of camera with far less
    > >interpolation (and zero color interpolation) than the S2 uses at 12MP.
    > > More pixels is bad, bad, bad, not good, unless optical resolution is
    > >higher and the S2 has about half the SD9's optical resolution accross
    > >the board (SD9 has 3.43M RGB triplets vs only 1.5M for the S2 Pro).
    > >Any image can be upscaled to any number of pixels.

    >
    > An amazing number of misleading statements for one paragraph. In actual
    > fact:


    Hi Dave
    Thanks for your post. As for me, I'm taking my own original advice to
    ignore in my OP.
    Thanks again John
     
    John McGraw, Aug 6, 2004
    #14
  15. John McGraw

    John McGraw Guest

    (Dave Martindale) wrote in message news:<ceodgp$dvp$>...
    > (Georgette Preddy) writes:
    >
    > >Here they are. Note, there are no such thing as hexagonal pixels, and
    > >the SD9 outputs 14MP pics straight out of camera with far less
    > >interpolation (and zero color interpolation) than the S2 uses at 12MP.
    > > More pixels is bad, bad, bad, not good, unless optical resolution is
    > >higher and the S2 has about half the SD9's optical resolution accross
    > >the board (SD9 has 3.43M RGB triplets vs only 1.5M for the S2 Pro).
    > >Any image can be upscaled to any number of pixels.

    >
    > An amazing number of misleading statements for one paragraph. In actual
    > fact:
    >
    > The SD9/SD10 have 3.4 million sensor pixels, lower than any other
    > current DSLR. Each pixel has 3 colour sensors, for a total of 10.2
    > million photosensors (a number you'll also see in reviews), but there
    > are only 3.4 million spatially-separate sensing locations and that's
    > what determines the ability to resolve fine detail. Competing DSLRs
    > have 6 million or more measuring locations. The Sigma raw processing
    > software can produce 14 MP images using interpolation, but this process
    > adds no useful detail at all.
    >
    > Other cameras use Bayer sensors that measure only one colour per pixel
    > but despite that yield the same resolution as a Foveon or B&W sensor
    > with the same pixel count. Georgette's references to counting 4 pixels
    > as "RGB triplets" or dividing pixel count by 4 to get "optical
    > resolution" are complete fabrications, with no basis.
    >
    > Standard resolution tests show that the Sigma cameras have lower
    > resolution than any of the other current DSLRs. This is true measured
    > "optical resolution", not what Georgette uses the same term for.
    >
    > The Sigma cameras do not use an anti-aliasing filter in the camera.
    > This gives images that *look* sharper than other 3.4 MP cameras, but at
    > the expense of inaccurate rendering of diagonal edges and thin lines,
    > and sometimes moire effects. Some people like the effect, some do not.
    >
    > The one advantage that the Sigma cameras *should* get from measuring 3
    > colours at every pixel is higher-resolution colour than a Bayer sensor.
    > However in practice the technology so far has a reputation for
    > inaccurate and blotchy colour rendition with some subjects.
    >
    > Now, there *are* people who like the Sigma cameras for the sort of
    > subjects they shoot. If you search the archives for this group in
    > Google, you'll find them. Just don't believe anything
    > "George/Georgette" writes. This person has been demonstrated to
    > misrepresent the results of tests, edit the text of other people he's
    > quoting to apparently support his position when they do not, and make up
    > explanations out of thin air.
    >
    > Dave


    Hi dave,
    Thanks for the reasoned advice & yes I ignore (& advise everyone else
    to) "their" posts.

    John
     
    John McGraw, Aug 6, 2004
    #15
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