poly/monochrome perception

Discussion in 'Photography' started by N, Oct 3, 2003.

  1. N

    N Guest

    Hello!,

    I'm hoping someone may be able to help me. I'm working
    on a little project, briefly it's about visual perception
    and communications, anyway, I'm going through some past
    work and keeping it up to date.

    I remember someone telling me about an experiment done some
    years ago. Two slide projectors were focused up on a screen,
    separate but identical monochrome images were projected
    together, but the viewer perceived the picture in colour.
    All the objects appeared to have the same colour as they
    did when the original photograph was taken.
    Does anyone remember anything about this or anything similar?
    I know about mixing light, but I was told that the slides
    were in greys, and I can't think how it would be possible to
    generate spectrum colour with only two lights.

    Unfortunately I hav'nt tried this experiment my myself, I'm
    wondering if the effect was more to do with guessing
    the colour of the objects on the screen by judging their
    contrasts and reflections (a bit like watching black and white
    TV)as opposed to the perception of colour of a specific
    wave length.

    Thank you,

    Nic
     
    N, Oct 3, 2003
    #1
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  2. I mentioned this, and perhaps others did too. It was a talk by Dr. Land, of
    Polaroid.

    I'm not an expert on the color perception, but I thoink it has something to
    do with what one expects to see. The photos that Dr. Land showed were of
    familiar objects. One was of a popular brand of laundry detergent.
     
    Marvin Margoshes, Oct 3, 2003
    #2
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  3. I heard about this before.

    In a lecture on Goethe's colour theory. Although I don't think it was Goethe
    who did this experiment, but his theory would explain the phenomenon.

    // Mads
     
    Mads Pedersen, Oct 3, 2003
    #3
  4. N

    N Guest

    Thank you for your responses

    I did Goethes colour theory which was great fun, but had to run
    around a couple of camera shops to find some second hand prisms!

    I just looked up Dr Land as suggested:-
    www.CPAS.anu.edu.au/publications/muses/Muses%20(1)%20May%201991.html
    and it outlines the experiment nicely. I'm going to aquire two
    projectors sometime before Xmas and have a go, to see what happens,
    I'll post the result, lousy or not!

    :)

    Nic
     
    N, Oct 3, 2003
    #4
  5. N

    Norman Worth Guest

    See Walker, J., Experiments with Edwin Land's Method of Getting Color Out Of
    Black and White, Scientific American, June, 1979 (The Amateur Scientist)

    and
    INTERFERENCE COLOR. Hiroshi Kubota in Progress in Optics: Vol. 1, edited by
    E. Wolf. North-Holland Publishing Company, 1961.

    LIGHTNESS AND RETINEX THEORY. Edwin H. Land and John J. McCann in Journal of
    the Optical Society of America, Vol. 61, No. 1, pages 1-11; January, 1971.
     
    Norman Worth, Oct 3, 2003
    #5
  6. Could it be possible that there were in actually three slide projectors with
    monochrome slides taken with red/green/blue filters and also r/g/b filters
    in the slide projectors??

    Alexander
     
    Alexander Dräbenstedt, Oct 3, 2003
    #6
  7. That may have been Land's starting point. The last example he showed had a
    yellow filter in each projector, though the two filters were not centered at
    the same wavelength. We still saw blues and reds! I don't recall him
    discussing the details of the spectral bandpass of the filters. There may
    have been some blue and yellow in the light that passsed through.

    I was working at the National Bureau of Standards then, and I talked about
    the demonstration with one of the color experts there. He was less
    impressed than I was, and said how it works was well known already.
     
    Marvin Margoshes, Oct 4, 2003
    #7
  8. Very unliely. It was at a national meeting of the Optical Society of
    America, in a hotel. I doubt that audience would have missed a third
    projector.
     
    Marvin Margoshes, Oct 4, 2003
    #8
  9. The voices in the head of Marvin Margoshes uttered these words to the
    inhabitants of alt.photography.
    One projector may have had a red filter and one a cyan filter. Since
    these are opposites, there may have been enough correction to create the
    other colors. The original images would have to have been shot with some
    color correction filters to achieve the full spectrum between the two
    composited images in the final projection.
    Keep in mind I'm not an expert on color correction, but have worked
    on some progects on my own for color printing digitally created photos.
    Way back in the days of the Atari 8-bit computers OSS BASIC XE and a B&W
    photo capture program, 3 primary color filters and a video camera (oh,
    and lots of time). It actually worked.

    --

    Robert S. Ely (Bob)

    New Lisbon Developmental Center Communications Systems Technician-3
    Work Phone: 1-609-894-4057 Work FAX: 1-609-726-0357
    ICQ: 33390750 Yahoo Messenger: rsely74
    MSN Messenger:

    Check out my photos:
    http://www.shuttercity.com/ShowGallery.cfm?AcctID=4359
     
    (Bob) Robert S. Ely, Oct 4, 2003
    #9
  10. Land started the talk with filters like the ones mentioned above, then
    showed results with different pairs of filters. The mind-boggling example,
    at the end, used two yellow filters that were not identical, though either
    one projected an image that loked yellow.
     
    Marvin Margoshes, Oct 5, 2003
    #10
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