Discussion: Why the dress is a novel illusion

There's something missing from discussion I've read, that us conniseurs at /r/illusionporn probably appreciate better than most people.We've all encountered objects that people disagree on the color of, but it's a subtle difference, like reddish orange vs orangish red. That's not an illusion, that's just where people draw the line.We've all seen objects that look completely different colors in different lighting. That's not new.We've all seen images that can be interpreted in different ways, with people seeing different things at first, and "swapping" for people when you look long enough. That's not new either.As far as I can tell, the dress is the first instance where different people look at the same photograph of an object and see dramatically different colors. Basically, we now know that #3 applies to color as well. Before it was only known to apply to motion and geometry. (Someone feel free to correct me if there's an earlier known instance.)So much of the discussion is on what color the dress really is (irrelevant) and how it's possible for #2 to apply (old news). Really the important thing, from an illusion standpoint, is not who's right, but that people so easily disagree.