In an attempt to explore "duplicity in two-dimensional surfaces," illustrator, designer and typographer Alex Trochut invented and patented a way to print two images on the same surface. His photography exhibit Binary Prints, puts the newly invented method to work, revealing a different portrait when viewed in the light or dark.
Have you ever wondered why computers always indicate that your hard drive or memory card has a smaller storage capacity than what's advertised on the box (and the card itself)? No, it's not because you got a defective card, it's not because your card came preloaded with a bunch of unwanted files (your hard drives, maybe), and it's not because the manufacturers are cheating you by skimping out on the storage space (well, not directly, at least). The reason has to do with math and marketing.