How good are you at picking shades?

Discussion in 'Australia Photography' started by Scott Coutts, Jan 27, 2004.

  1. Scott Coutts

    Scott Coutts Guest

    Scott Coutts, Jan 27, 2004
    #1
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  2. Scott Coutts

    Dave Ello Guest

    http://www.network54.com/Hide/Forum/thread?forumid=47211&messageid=1075085896

    Hi Scott,

    Yes, very interesting indeed. I certainly couldn't see it until I did as
    others did and drew the line from A to B. Of course this has generated some
    crunching in my limited grey matter about the implications of this and any
    possible relationship with my photography.

    Cheers,
    David
    P.S. I never did get back to you to thank you for your long dissertation on
    making a pan setup. I'll have a good think about all that and let you know
    how I go. Many thanks!
     
    Dave Ello, Jan 27, 2004
    #2
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  3. Scott Coutts

    cole Guest

    The guy who did that is so cool

    has more demos here
    http://www-bcs.mit.edu/people/adelson/illusions_demos.html

    his main page is here
    http://www-bcs.mit.edu/people/adelson/
     
    cole, Jan 27, 2004
    #3
  4. Scott Coutts

    Miro Guest

    Miro, Jan 27, 2004
    #4
  5. Scott Coutts

    Scott Howard Guest

    Actually, the A and B squares are NOT the same shade. The A square is
    black, whilst the B shares is white. The shadow cast onto the B square
    doesn't change it's underlying colour, and your brain is smart enough to
    realise this and thus report to you that they are a different colour.

    If you look at the green clyinder your brain will probably report to you
    that it is a constant colour, with the different shadings being caused by
    the angle the light is hitting it. Obviously photoshop will disagree with
    you as the left hand side of it is far darker than the right hand side...

    Your brain doesn't simply report to you on what it sees, but it first
    interprets that information for you into a more useful form. Hold two pens
    in front of you, one twice as far away as the other. Your brain doesn't
    tell you that the pens are different sizes (as they appear to be), but
    instead it tell you (correctly) that they are the same size, only one is
    closer than the other.

    That said, cool illusion :)

    Scott.
     
    Scott Howard, Jan 28, 2004
    #5
  6. Scott Coutts

    max morrison Guest

    The right side of my brain agrees with you, but the left side
    tells me that it's a 2D computer-generated graphic
    (giving the illusion of 3D), and that no shadow actually exists,
    just the illusion of a shadow.
     
    max morrison, Jan 28, 2004
    #6
  7. Scott Coutts

    Scott Coutts Guest



    Yep, and here's some more, for people who are interested more in the
    theory of how they work:

    http://www.colorcube.com/illusions/illusion.htm

    Well, that one doesnt have much theory. The rest do though!

    Here's some info on why they happen:

    http://www.du.edu/~jcalvert/optics/illusion.htm

    This page also talks about Poggendorff's illusion of the intersection of
    diagonal and vertical lines:

    "Poggendorff's illusion is very famous. Line 2 is actually
    the continuation of the line on the left, although line 1
    appears to be. This illusion is counteracted in the British
    Union Flag by displacing the arms of St. Patrick's cross
    on either side of St. George's cross so they appear to be
    in the same line. Greek temples were designed with
    deliberate distortions to make the building appear
    correctly. Columns were given entasis, a slight swelling
    in the middle, so they would look straight, and architraves
    were cambered up slightly in the center so they would appear
    straight"

    Apparently, they still have no explanation for why that works...

    Here's some more of them, along with a PDF paper about it.

    http://persci.mit.edu:16080/gaz/
     
    Scott Coutts, Jan 28, 2004
    #7
  8. Scott Coutts

    Scott Coutts Guest

    Ok, with my sciency objectiveness hat on....

    ....Yes, they are!
    There is no shadow! Its the picture that is in question here, not the
    'original scene'... but that said, I know what you mean :)
    That doesn't change the fact that it is NOT the same colour all the way
    around. Your brain is tricking you into thinking that it is the same
    colour, because it is used to seeing it that way. If it were a real
    object, then it sould be the same colour. But it's a picture. The same
    as in a photo - the colour is defined by the pigments, not by the real
    world.
    No, that's not right. Your brain distorts the physical reality.
    Shut one eye and it makes it harder :) But this is a different issue
    from the colour perception.
    True... and although your brain fools you into thinking the colours
    arent the same, you'd have a hard time if it didnt work that way :)

    By the way, apparently, some painters are able to see the colours for
    what they are, rather than what most people's brains tell them it
    'should' be.

    Scott.
     
    Scott Coutts, Jan 28, 2004
    #8
  9. Scott Coutts

    Scott Coutts Guest

    Yes - and one thing I find interesting is that, even though part of your
    brain 'knows' that there's no shadow there, you still can't convince
    yourself that the colours are the same... :) This is different from the
    'ambiguous figure' illusion. Do you know the 3D representation of three
    faces of a cube, drawn so that you're looking directly at the point of
    one of the corners? You can think about it so that you're looking at it
    as though it from the inside or the outside, if you know what I mean.
    This makes the 3D figure look 'sunk in' or 'raised up' from the paper. I
    hope that makes sense. For that one, you can convince yourself that it
    goes either way.

    Scott.
     
    Scott Coutts, Jan 28, 2004
    #9
  10. Scott Coutts

    Miro Guest

    The concept of a shadow doesnt alter the mechanism.
     
    Miro, Jan 28, 2004
    #10
  11. Scott Coutts

    Scott Howard Guest

    If there is no shadow, then there are no "squares". If you're looking
    at a 3D image, then you can consider the 4-sided boxes to be squares, the
    green lines-and-a-circle-thing to be a cylinder, and the colour difference
    to be from a shadow.
    If you're looking at a 2D image then there are no squares, there is no
    cylinder, and there is no shadow. You can't have it both ways :)

    Regardless of what there is, your brain sees squares, it sees a cylinder,
    and it sees a shadow. If not, why did you call them squares?
    Photoshop has no brain (as proven by what it does when you select
    Auto-levels), and thus sees a 2D object with no difference in colour between
    the A area and the B area.

    Scott.
     
    Scott Howard, Jan 28, 2004
    #11
  12. Scott Coutts

    Scott Coutts Guest

    Certainly... but the shapes of them dont matter. In fact, you're right,
    they're not squares.
    Again, it doesnt matter what shape they are.
    What defines the colour of those shapes? I define it physically (it
    doesnt have to be defined this way, but that's just how I choose to
    define it). It's the wavelength of light emitted from the object being
    viewed. You're viewing it on your screen, and the screen is shining the
    same coloured light at you when you look at both 'shapes'. It's the same
    colour!

    Anyway, we're arguing the same point here! :) Really, our discussion is
    about how we're defining the 'colour' of the picture. I'm saying that
    it's colour is decided by the picture.

    Scott.
     
    Scott Coutts, Jan 28, 2004
    #12
  13. Scott Coutts

    Miro Guest

    Colour is and always will be relative. In addition to which you can "see"
    the difference between two green objects and swear they are the same hue,
    till you see one of the objects next to a darker strip. Then you may set the
    two green hues apart.
     
    Miro, Jan 28, 2004
    #13
  14. Scott Coutts

    Scott Coutts Guest

    Still, that's in agreement with what we're saying. Still, it depends on
    how 'colour' is defined. They'r only relative because our brains modify
    what is actually being detected and give us a 'faulty' version of what
    is really there. Faulty, but nonetheless useful most often.


    Scott.
     
    Scott Coutts, Jan 28, 2004
    #14
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