There is a famous video on Youtube about how the X-ray contact lenses can see the normal playing cards without invisible ink marks. A lot of guys have watched this video and believed that the X-ray contact lenses is amazing.
Many guys begin to search such great X-ray contact lenses online. However, they failed. Some guys buy some so called X-ray lenses from the companies who said to have that advanced technology contact lenses, but they felt disappointed because the products they got don't work at all.
In fact, the so called X-ray contact lenses that people buy can't see the playing cards, not because the cards are marked or not. It's the X-ray contact lenses that doesn't exist in the world so far. We don't know if people can get such a technology to make the contact lenses to see all the playing cards in the future. But now, there's no such thing exist for sure. And all that you see in that video just done with photoshop.
If you believe in the X-ray contact lenses, you can just think about one questions. If it can see through the clean cards without invisible ink marks, why can't you see the poker table directly but just the number of the cards?
