Feeling Scrooge-y? Here's a basic way to be judgmental about your local Christmas decorations. Not only are you up in other people's business, even the act of scrutiny is as obnoxious as it is possible to be — it literally involves sticking your tongue out at people.
These days, some people use LED (light emitting diode) lights tp spread their Christmas cheer. These are more expensive than typical lights, but run longer on less electricity. But once people began making use of LED lights in their homes, they noticed a down side. Some people experienced a constant, annoying flicker. It wasn't so bad when people stayed still, but became more noticeable as they moved around. And it's more noticeable yet when you do the most juvenile thing you can do. Some people call it a "bronx cheer," and some call it a "zorbit." Where I grew up it was called a "raspberry." Basically, it's when you stick out your tongue and make a fart sound. Stand about ten feet away from a string of LED lights (or an LED lightbulb, or the LED lights on a clock radio), and make the noise while staring fixedly at the lights. They will visibly start flickering and jumping around.
Why? For the same reason that an LED light, when filmed, will appear to be flickering. The light is constantly flickering — just at a speed far to fast for you to see. When the raspberry starts moving your head around, your eyes will sometimes lock back onto the lights as they flicker off and as they just begin to flicker on. You've provided your own strobe effect. Likewise, a camera filming at 24-frames a second will sometimes capture that fraction of a second when the light is off. When the film is replayed, the flickering — which actually happens 60 times a second — is artificially elongated on film and becomes noticeable.
(By the way, the raspberry is an easy way of creating a strobe effect for nearly everything. You'd be surprised how different the world can look when your head is vibrating with scorn. Just be a little careful who is in the path of your "strobe." And be prepared to run fast.)