The tools cinematographers use to light scenes are seriously bizarre. I know, I know. We see this stuff every day and have become blind to their peculiarity, but think about what a beginner or a friggin' alien might think when catching a glimpse of a cinematic lighting set up for the first time. Umbrellas, ring lights, and snoots—super weird, but perhaps not as weird as the egg crate grid. It may look like one of those decorative paper chains you made in elementary school, but don't let its simple design fool you. This thing is a powerful light modifier that can give you a lot more control over your lighting. To find out how to put it to good use on set, check out this video from David Bergman of Adorama TV.
The design of the egg crate grid is deceptively effective. I mean, the entire thing is just a bunch of squares, so I'm sure novice filmmakers look at it and go, "What's the big deal?"
Well, the big deal is that it does a really great job of directing light. By pushing light forward and blocking it from going sideways, these kinds of grids allow you to 1.) direct light easier, and 2.) keep light contained. In other words, slapping a grid on your softbox, which softens and disperses light over a wide area, will allow you to point that softened light in a specific direction.
Egg crate grids are effective, portable, and super cheap, so if you're hankering for a little practice time with some lighting gear, you can't go wrong with one of these babies.