eli5 How does projectors projects black in a bright room?

Question

I am in psychology class, the light’s are on and I clearly see this black squares on white background. How is this possible? https://www.instructables.com/Optical-Illusion-Black-Squares-and-Gray-Dots/

In: 1

Answer 1

Another [optical illusion](https://en.wikipedia.org/wiki/Checker_shadow_illusion) explains that.

The projector, of course, can’t project darkness. However, it can make everything else brighter, so the parts that aren’t illuminated seem black. That’s also the reason why projectors don’t work in sunlight because they’d have to be blindingly bright to get enough contrast.