Antoine D sent me this wonderful illusion.  Amazingly, the discs and chess pieces are the same shade and colour!

My thanks to Bart Anderson for permission to share the image, and here is the paper about it:

Anderson, B.L.,& Winawer, J. (2005)  Image segmentation and lightness perception.  Nature434, 79-83.

chess

32 comments

  1. Wow! Even though I know these types of things work, I still couldnt believe it until I copied it into Paint so I could drag and compare. Excellent!

  2. I don’t know about my eyes, but I won’t believe anything you write after last Friday’s puzzle fiasco.

  3. I’m not getting this. Are you saying that, for example, the black king is the same shade as the white king or that the black circles are the same shade as the black chess pieces?

  4. Please help me – I have similar things before, but I don’t know how to “see” it this time.

  5. I don’t get it. If I test the pixels on the lightest area of the lightly shaded circles/chess pieces it’s almost pure white (RGB 1,1,1). If I test the pixels on the darkest area of the darkly shaded circles/chess pieces it’s almost black (RGB 248,248,248). How did you verify that “the discs and chess pieces are the same shade and colour!” ?

    Kind regards – Jakob

    1. I’ve satisfied my own question and can possibly satisfy yours. I viewed the images on my monitor screen and with a perforated card, just looked at the same part of the black and white queens simultaneously. They are the same! Fantastic illusion.

    2. Ah.. got it now!
      A specific pixelposition in one part of the “white” chesspiece is the same RGB value as the same pixel on the “black”.
      Thanks for the explanation 🙂

  6. Since I am the author of this paper and the originator of the illusion, you might consult the original paper found here:

    Anderson, B.L.,& Winawer, J. (2005) Image segmentation and lightness perception. Nature, 434, 79-83.

  7. This is an example of an “optical illusion” which is something that the human eye simply cannot see properly.

    An easy way to understand such illusions is to remember that a “picture is worth a 1000 words”. Thus an optical illusions is best thought of as a very long tongue twister.

  8. It’s a good one. When I stare at the ‘white’ bishop on the right it turns black. Very clever. It doesn’t work for the other pieces but I get the point.

  9. Oh,I see what you have done.

    The textured ‘seed’ images were generated in Matlab as grey-scale noise with a specified
    power spectrum that varied as (1/f4), 512 x 512 pixels. The different frequency
    components were summed with random phases and orientations. The target and
    background images were spatially identical to the seed image, but differed in the range
    of luminance values. The target image had 99% Michaelson contrast, with intensities
    ranging from 1 to 96 cd. For the surrounds, the luminance ranges were compressed and
    either shifted up or down. For the light surround (which gives rise to the percept of a
    dark target seen through light clouds), the range was 36 to 96 cd (45% contrast) and for
    the dark surround, the range was 1 to 77 cd (98% contrast). The illusions (static, Fig. 1;
    moving, Supplementary Video 1) were created by aligning the target texture with one of
    the surround textures and then showing the target through a circular aperture on either
    the light or dark surround. The multiple apertures in Fig. 2 represent the effect of
    motion. For the control demonstrations (Fig. 3), the identical targets were used but the
    surrounds were rotated by 908. This caused the polarity relationships between the target
    patch and the surround to vary, destroying the percept of transparency and the lightness
    illusion.

    Quite straight foward when you think about it

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

w

Connecting to %s