Sigma/Foveon Questions

Discussion in 'Digital Photography' started by Bubba, Apr 17, 2010.

  1. Bubba

    Martin Brown Guest

    I suggest that you learn what a pixel means - that would help.

    The Bayer grid contains filtered photosensor sites. It takes the data
    from several of these to construct any pixel in the final image.
    A monochrome pixel is a pixel, but only if the image can be interpretted
    as an image in its own right. A Bayer mask image looks pretty strange if
    displayed as colours without demosaicing. If you split a 12Mpixel Bayer
    mask image into the four separate colours of 3Mpixel each then you can
    call them pixels in the various monochrome representations of colour
    images. When they are still all mixed up it is misleading to call them
    pixels because that has an implication of all being channels measured.

    By any reasonable definition a photosite on Bayer sensor array is only
    measuring one colour out of R,G,B or possibly two in the case of low
    light modified C,M,Y,G filters. That is necessarily losing information
    about the true luminance of the image.

    There are 12M sensor sites, but each one is measuring only a part of the
    image data. In particular there is a difference in the spatial
    resolution of the red and blue sensors compared to green. And of all the
    colours when compared to an unfiltered sensor array of the same
    dimensions. Demosaicing can fix most of this up which is why the Bayer
    pattern is useed. It works because the human eye is ropey at colour
    resolution.

    In common computer imaging usage a pixel is generally taken to mean a
    monochrome image of 8, 16 or 32 bits, or a colour pixel with either
    palletted 8 bits, 16bits (R,G,B = 5,6,5), 24bits (8bits for each of
    R,G,B), 48bits (16 bits each for R,G,B).

    The Bayer mosaic is none of these as there are a lot of implicit zeroes
    in the measurement grid and a distinct green bias due to the twofold
    excess of green pixels in the grid.

    Regards,
    Martin Brown
     
    Martin Brown, Apr 26, 2010
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  2. No, I'm describing what happens in the typical 12MP DSLR, which has 3
    million red-sensitive photo-sites, and delivers 12 million full-colour
    output pixels in its JPEG file.

    David
     
    David J Taylor, Apr 26, 2010
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  3. I am not making anything up, that is just how it is, each colour sample
    is a vector of 3 unique scalar components, red, green and blue.

    Since you seem to be unique in your ignorance, try reading:
    http://en.wikipedia.org/wiki/Pixel

    Wiki may be prone to errors, but in this case it is spot on:
    "the term pixel is used to refer to a SINGLE SCALAR element of a
    multi-component representation".
     
    Kennedy McEwen, Apr 26, 2010
  4. A monochrome pixel is a pixel in a monochrome image.
    For those lagging at the back with Ray, we are discussing colour images,
    not monochrome images.

    As such a monochrome sensel is NOT a complete pixel, using your
    definition of pixel, it isn't even the luminance component of a complete
    pixel. It *IS* incomplete.

    It is a complete pixel in the conventional definition, but three such
    pixels (picture elements) are required for true colour samples.
    Demosaicking of the Bayer CFA output creates the missing two pixels by
    interpolation.
     
    Kennedy McEwen, Apr 26, 2010
  5. No, you seem to be trolling again though.
     
    Kennedy McEwen, Apr 26, 2010
  6. Bubba

    Guest Guest

    technically they aren't pixels on the sensor but very few people make
    the distinction. the number is the same either way.
    a little, but not as much as some people think.
    they're not taken independently of the green.
    yes, and it works well.
    or cmyk or rgba or numerous other variants.
    it's a single spatial element of an image, whether it's on the sensor
    or in the image.
     
    Guest, Apr 26, 2010
  7. Bubba

    Guest Guest

    it doesn't upsize the red and blue. each pixel is processed with its
    neighbors.
     
    Guest, Apr 26, 2010
  8. We start with 4Mp of red and blue, we end up with 12Mp of red and blue.
    Irrespective of what else is used in the interpolation that is *STILL*
    interpolation and upsizing.
     
    Kennedy McEwen, Apr 27, 2010
  9. Bubba

    Guest Guest

    interpolation yes. no upsizing since it's already the correct size.
     
    Guest, Apr 27, 2010
  10. Bubba

    Mr. Strat Guest

    Do any of you people ever create images - or do you just masturbate
    over technical crap?

    Foveon has proven itself to be a failure.
     
    Mr. Strat, Apr 27, 2010
  11. Bubba

    Ray Fischer Guest

    You're too much of a stupid ashsole to be condescending.
    An outright lie.

    You're "confused" becuse you think that a pixel must have a certain
    amount of color information. In fat it need contain no color information
    at all.
    Wrong.

    No "if".
    Non sequitur. The definition of pixel has nothing to do with any
    sensor type.
    You're not reasonable.
    LOL!

    Tell us: Where did you get your degree in computer science? Where
    did you get your education in computer graphics? I got mine from
    Stanford and Cal Poly and from working in the graphics business.
     
    Ray Fischer, Apr 27, 2010
  12. Bubba

    Ray Fischer Guest

    You are pushing your religion. I'm trying to educate you.
    A sensel isn't ANY kind of pixel.
    All pixels are "complete". Your claim is as absurd as claiming that
    13 isn't a "complete" number because it's missing some factors.
     
    Ray Fischer, Apr 27, 2010
  13. Bubba

    Ray Fischer Guest

    Sensors are not pixels. They are completely independent concepts.

    You are confused because you think that because a pixel isn't what you
    think it _should_ be then it must not be a pixel. It's like insisting
    that because 2+5 is not equal to 6 then 6 must not be a proper number.
     
    Ray Fischer, Apr 27, 2010
  14. Bubba

    Ray Fischer Guest

    The fact that you keep throwing in new terms and making up new rules
    is ample evidence that the only troll here is you.
     
    Ray Fischer, Apr 27, 2010
  15. Bubba

    Ray Fischer Guest

    That you insist that your made up nonsense is not made up doesn't say
    much for your sanity.
    Note that "color sample" is not "pixel".
    But that's only one of many different possible representations for a
    COLOR (not a pixel). In the CMYK space there are four components.
    You could also use a n-component color system of frequencies and
    intensities.

    Obviously you're wrong, and you're stupid for thinking that the way
    of describing a color has anything to do with the color itself.
     
    Ray Fischer, Apr 27, 2010
  16. Each sensitive element is the same physical size as the resulting RGB
    pixel, yes. But the spacing of the pixels is not. For each of the 12M
    output pixels, there are only 3M red sensitive locations, at twice the
    physical spacing of the 12M pixels. Therefore the red information in
    between those red-sensitive pixels is obtained by spatial interpolation.
    Isn't 3M => 12M upsizing?

    Cheers,
    David
     
    David J Taylor, Apr 27, 2010
  17. You can see some of my images here:

    http://www.satsignal.eu/Hols/2010/NorthernNorway/index.html

    mostly taken with a Nikon D5000 chosen for its high image quality,
    relatively good performance at high ISOs, it's movie capability, and its
    swivel finder. Whether it has a Bayer or Foveon sensor doesn't bother me.

    Cheers,
    David
     
    David J Taylor, Apr 27, 2010
  18. Bubba

    Guest Guest

    each pixel has the same spacing, although the filter in front of it
    varies.
    there are other pixels in between the red pixels.
    the spatial location of any given pixel is the same, it's the contents
    that is interpolated. think sparse matrix. it's not upsizing a small
    3mp matrix into a bigger 12mp matrix.
     
    Guest, Apr 27, 2010
  19. []
    "Pixel" may have a number of meanings - there is the element in a JPEG
    file which has three components (R, G & B), and there is the region on a
    sensor which received light and turns it into an electrical signal. The
    latter are sometimes called sensels, although that's not a term I tend to
    use a lot.

    How does your definition of a pixel compare with this one?

    http://en.wikipedia.org/wiki/Pixel

    Cheers,
    David
     
    David J Taylor, Apr 27, 2010
  20. Bubba

    Ray Fischer Guest

    No. No pixels are being added to the image. Additional information
    is being added to existing pixels. No additional pixels are being
    added.
     
    Ray Fischer, Apr 27, 2010
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