Quote:
Originally Posted by robotparker
Here's another example that might be clearer:
We all know snow is white, but if you make an image of snow not being hit by direct sunlight, it's probably gonna appear to be a little blue. The original image of the dress faces similar challenges: the actual dress appears to not be directly lit, but the background is very bright which further exacerbates the poor white balance and exposure (quick side lesson: try photographing someone standing in front of a bright window. you can either correctly expose your model, or correctly expose the outside of the window, but not both).
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I also like your snow example, since our brain does the same thing. A friend took the girls from my illusion and put them into two snowy boston scenes to make a version of my illusion using natural images, its nice because as you say, we know snow is supposed to be white. But snow that is illuminated by shadow (which is ambiently lit by scattered refracted diffuse blue skylight; one end of the daylight spectrum) will have a blue bias (as you say), and snow illuminated by direct sunlight (especially early and late in the day) will have an orange bias (other end of the daylight axis). Just as you white balance for this, Our brain has an internal model to white balance for this. the result is that if I put the dress on a girl in these two conditions, in one case your brain will remove what it expects to be a blue bias present (gives WG dress), and in the other expects to be an orange bias (gives BB dress):
Does this illusion work for you? do you ever see a Blue-Black dress? how about in my other illusion?