system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do cinematographers do forced perspective while keeping everyone in focus?

I've heard of this technique before, where you place one actor much farther from the camera than the other to make them look much smaller by comparison. It makes perfect sense to me except for the question in the title.

Wouldn't having one actor near and one far require the camera to focus on the nearer actor leaving the far away actor blurry and out of focus, or vice versa?
gpt
By using a higher f-stop (smaller camera aperture) and raising the amount of light.

The reason things get out of focus, and the reason we need to focus in general, is because light bouncing off the same object comes into the camera from all different directions and we need to focus that into a single point on the film/sensor. The smaller the hole that the light passes through, the fewer possible directions it can be coming from and therefore the less the lens needs to focus the light. Small holes mean less total light getting in though, so you have to turn the lighting up really bright to compensate.