Courtesy of Rhett Allain
But what about the colors of a video projector? It basically does the same thing. However, instead of a bunch of little RGB lights, it projects RGB colors at different locations on the screen.
Projecting the color black
Now we’re ready for the fun stuff. How does a video projector emit black light? The black light would be the absence of any light, as we saw before. How do you not project anything? First, let’s consider a screen like a television. If you have three small lights (red, green, blue), you can make a small black spot by simply turning off the lights of all three colors at that location. Boom, it’s black!
So is it possible to just turn off the projector to make black? That can’t be right, right? If that were the case, you wouldn’t be able to tell the difference between a projected black color and the screen without the projector even turned on. Yes, that’s exactly how it works.
Check it out: In the image below, I’m projecting a half black and half white slide. The slide takes up most of the screen.