Bayer with NO anti-aliasing (Kodak Pro 14n)

Discussion in 'Digital Photography' started by K2, Nov 28, 2003.

  1. Certainly not when you use a DSLR with a blurry sensor.
    That's worth $2500. Why not buy 6 pro lenses instead?
    Not with a blurry sensor they don't.
    With a blurry sensor? Irrelevant.
    That's because your 10D is completely blind to features less that 4 pixels
    wide.

    And you forget the main reason 10D owners buy L glass: It's a fashion
    statement.
     
    George Preddy, Dec 12, 2003
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  2. K2

    Guest Guest

    You really are excelling yourself now Georgey boy.
    Go on post a link to another of your horrid pictures again, I like it when
    you do that.
    How about the blue/yellow tiger one?
    Or the portraits with weird skin tones.
    Or something with some near horizontal or vertical lines in it.
     
    Guest, Dec 12, 2003
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  3. Click the links I provided first.

    14n:
    http://www.steves-digicams.com/2003_reviews/pro14n/samples_new/C7SG0367.jpg

    Compare to medium format film quality (unfortunately heavily JPEG'd,
    originally): http://www.pbase.com/image/23733001

    Canon 10D images (hard to find, full size) are awash in Bayer color
    artifacts too: http://www.pbase.com/image/23908485

    You'll see how poorly these outrageously expensive Bayer (good camera
    bodies, shame they only have an interpolated sensor inside) cameras really
    perform. Image quality from Bayers is very poor, awash in color artifacts,
    but given 13.72M sensors and massive downsizing (to 3.43MP), some of the
    artifacting can be averaged out. Bayer is still no where even close to
    color 35mm film, though when imaging a B&W target (and after being digitally
    converted to B&W to eliminate any color moire) in can approach the B&W
    resolution of 35mm color film, but probably still not 35mm B&W film.

    Sigma DSLRs (only) approach medium format color film, when enlarged less
    than 40 inches... http://foveon.com/faq_technology.html#FAQ_tech_13
     
    George Preddy, Dec 13, 2003
  4. K2

    Don Stauffer Guest

    Lets not confuse resolution with detection. By that reasoning, we
    cannot see stars, because the human eye cannot resolve a feature size
    anywhere near the angular size of a star.

    Contrast of image of subpixel object is reduced, but if original
    contrast is high enough, you will see it- camera is not 'blind' to it.
     
    Don Stauffer, Dec 13, 2003
  5. Well, you might see something, but you won't see "it." If a thin line of
    color, say razor thin CA in this case, falls as a single pixel wide line on
    the sensor, the SD9 will resolve its color perfectly and display it
    perfectly (even if it is less than a pixel wide as long as it is the
    dominant color), while a Bayer sensor will show it as a blurred collection
    of mosiac color artifacts, as each sensor alternates from red to gren to
    blue as the thin line falls across the sensor, the rainbow of these randomly
    colored artifacts (in that, they have no correlation to the real color) then
    get partially "borrowed" into adjacent pixels that didn't even sense it,
    bluring anything less than 4 pixels wide unrecognizably. It would simply be
    protrayed as mostly random color artifacts blurred partially into
    surrounding pixels.
     
    George Preddy, Dec 14, 2003
  6. This analyzis is totally correct. And this shows a theoretical advantage
    of Foveon over Bayer. I don't really think that anyone can argue that you
    are wrong here.

    But ... there are some things to take inte account

    * A sampling system shall use an anti alias filter. Therefore, no
    thin one pixel lines will exist on the sensor. I know you don't agree
    (yet?), but it is a fact IMHO.
    * A good Bayer interpolation algorithm shall do hue smoothing. Therefore,
    the multi colored mosaic will not either exist in the final picture.
    In practice, there might be some residue of color artefacts.
    * Real world scenes (usually) are much nicer to the Bayer sensor than
    the example you described.


    Roland
     
    Roland Karlsson, Dec 14, 2003
  7. K2

    Mike Engles Guest

    Hello

    Most of the images on the Dpreview of the Canon 300 have purple/green
    artifacts, just like the SD9. Th Canon ones are just blurred away.
    You can see the artifacts, where some sort of sharpening has taken
    place. It is a exactly similar, but not to the same degree as the SD9.

    It has to be said that at 100% viewing it is not noticable. The images
    just lack detail.

    The choice seems to be apparent sharpness with jaggs(SD9) or no jaggs
    and blurriness(Canon et al).

    As far as I can see, they all have to do better.


    Mike Engles
     
    Mike Engles, Dec 15, 2003
  8. Not totally. The word "perfectly" doesn't fit reality. Since the color
    sensitivities of the Foveon sensors are determined by the depth of
    silicon between them, they can't be tailored very well to make color
    separation effective--hence lousy, not perfect, color resolution.

    No free lunch. Even if real color filters could be introduced into a
    stacked-element sensor, the lower ones would still be limited to
    whatever got through the upper ones. Not insurmountable, in that film
    manages to deal with the same problem. But nobody has tried it so far.
    I just did, but who am I?
    It is not just your opinion, humble or otherwise. It is a mathematical
    fact that data at beyond-Nyquist frequencies, if allowed to reach the
    sampler, will produce below-Nyquist artifacts that cannot be filtered
    out afterward.




    Rodney Myrvaagnes J36 Gjo/a


    "In this house we _obey_ the laws of thermodynamics." --Homer Simpson
     
    Rodney Myrvaagnes, Dec 15, 2003
  9. K2

    Guest Guest

    Anyone else like the irony of George posting this about ANYBOBY.
     
    Guest, Dec 15, 2003
  10. K2

    Guest Guest

    Err, it's not Sweaty Betty.


     
    Guest, Dec 15, 2003
  11. K2

    Guest Guest

    As long as it doesn't land in the gaps between the sensors....
     
    Guest, Dec 15, 2003
  12. K2

    Guest Guest

    Yep, the bayers kick the aqss of the foveon again. Not too bad ISO 1600 10D
    shot, but I spose you hoped we wouldn't notice that and assume it was ISO
    100.
     
    Guest, Dec 15, 2003
  13. K2

    JB Guest

    As has been pointed out *many* times, the lack of an anti-aliasing
    filter introduces aliasing artifacts which can be much worse than just
    jaggs - e.g. low frequency signals created by the sampling process
    which cannot be filtered afterwards.

    /JB
     
    JB, Dec 15, 2003
  14. I just tried to be nice to George :)

    You are entirely correct BTW.

    My point was that George's reasoning was theoretically sound.
    The Bayer filters has the theoretical problem that he points out.
    In practice, this theoretical problem is not all that large.
    In practice, the SD9 does not have a perfect RGB sensor either.


    Roland
     
    Roland Karlsson, Dec 15, 2003
  15. Not really.

    The SD9 artefacts cannot be removed.

    The Canon et al "blurriness" can be improved, using sharpening.
    For some reason, Phil at DPReview chooses not to apply any
    post processing before publishing pictures. This is not fair to
    cameras where you are assumed to do post processing for best result.


    Roland
     
    Roland Karlsson, Dec 15, 2003
  16. K2

    Noel Guest

    There you go again, Steve, thinking that you and the 'whole world' are
    synonymous. Didn't you learn anything when we schooled you in
    comp.sys.amiga.advocacy?
     
    Noel, Dec 15, 2003
  17. K2

    JPS Guest

    In message <>,
    The texture of entire objects are screwed up by the SD9; not just edges.
    Look at any distant trees, or brick walls, or shingled roofs; if they
    are in focus, they have false texture.
    --
     
    JPS, Dec 15, 2003
  18. K2

    pehache Guest

    That's true that the 10D AA filter has been set to remove most of the
    chromatic artefacts, but not all. And at the expense of the
    resolution, as you point out. This is not not the case for most of the
    Bayer cameras: generally, vendors prefer to have a higher resolution
    and more chromatic artefacts.

    No, you make a confusion between aliasing and stair effects. True
    aliasing results in *low* frequency artefacts: there are very probably
    some SD9 images with such artefacts, but most of time I don't see such
    ones.

    What is always visible on SD9 images are the stair effects along sharp
    edges which are not perfectly horizontal or vertical. I agree that
    this is not very esthetic, but it is only a perceptual problem, which
    is the consequence of coding high frequencies with a reduced amount of
    pixels. Try upsampling the SD9 images to 6Mpix: if done properly the
    upsampling doesn't destroy any information, and it removes most of the
    stair effects.
     
    pehache, Dec 16, 2003
  19. (pehache) wrote in
    Hmmmm ... yes it is true that aliasing results in low
    frequency artefacts. But - it is not as easy as that.
    You also have to take the phase into account. Phase errors
    (due to aliasing) will give stair effects and other
    funny stuff that affects only some few pixels.


    Roland
     
    Roland Karlsson, Dec 16, 2003
  20. K2

    pehache Guest

    No. Still the same confusion.

    A frequency is either aliased (resulting in a low frequency
    artefacts), or unaliased. This is completely on/off effect: if
    unaliased (lower than Nyquist), it is perfectly coded from the
    information theory point of view, including its phase.

    The point is that it is not because a frequency is perfectly coded
    that it will be nicely displayed. Frequencies close to Nyquist (but
    still inferior to) are actually very poorly *displayed*, this is a
    known effect in signal processing, resulting in stair effects and
    other funny things as you said. Usually, it is recommended, to have
    nice displays, to have a Nyquist at least twice the dominant frequency
    of the signal. This can require upsampling prior display.

    That's basically why the Sigma sofware offers the possibility to
    output upsampled files. IMO this should be the default behavior. It
    does not add any information, but the files are much nicer to observe.

    The upsampling can be done afterwards, but to upsample properly
    frequencies close to Nyquist, one need a very good algorithm (bicubic
    may be not enough efficient). It is probably better to make the
    upsampling stage inside the Sigma software (I assume that they have
    chosen an appropriate algorithm).
     
    pehache, Dec 17, 2003
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