Take a look at this picture. Who do you see? If you see Marilyn Monroe, you may be shortsighted.
This optical illusion is made possible by a technique called “hybrid imaging.” It takes advantage of the way humans process visual stimuli and produces an image that changes based on the distance the image is viewed. Those with normal vision will only see the high spatial frequency image (Einstein) when viewed up close. On the other hand, those who are shortsighted will see the low spatial frequency image (Marilyn Monroe). If you can only see Einstein, stand up and walk back a few meters to get a glimpse of the lovely Marilyn.
…or take a look at a tiny version of the same image.
A breakdown of a different hybrid image of Einstein and Marilyn Monroe can be found on Wikipedia:
If you look at the picture below from a close distance, you will see an image of a Japanese castle. But if you take a few steps back, the castle disappears and you’ll be left with a view of Kinkaku-ji, Kyoto’s most famous temple.
You can check out some more hybrid images at the MIT Hybrid Gallery. Just make sure you’re in a place where you can get up and repeatedly walk away from the computer…you might get some odd looks if you look at these images in a public place.