ILLUSION: SHADES OF GREY
Hold a finger between your screen and your face such that it blocks out your view of the dividing line between any two shades of grey in the image. Close one eye if you need to. The difference between the two shades should be hard to detect.
When viewing the image normally, the steps in colour are quite clear- the human eye generally picks up contrast quite well. We do however become far less able to resolve contrast between two fields if the intersection between them is obscured.
I created this image on MS Paint pretty quickly. I’ve been wondering whether making an image with with gradients of different colours (ie. green to blue, red to yellow) would work. Try to make one yourself, and post up a link to it.
Simple optical illusions like this are an interesting reminder of how easy it can be to fool our senses, and why some camouflage can work so well. This is why good science is so damn useful. The process of asking clear questions, designing careful experiments, and being open to criticism helps to ensure your are not being deceived (perhaps by yourself).
Sometimes you just can’t trust your own eyes.