Spontaneity Rules the Day
Kauffman may have written a very tight, dense script filled with character and wit, but that doesn't mean everything you see and hear was just a recitation of it. As a director, Gondry valued giving actors the freedom to improvise. This sometimes happened in specific locations, like when Gondry heard people talking about elephants walking through New York City and grabbed the crew to get some impromptu filming done.
There's also that scene on the snowy beach—which wasn't supposed to be snowy at all. But instead of waiting for the snow to melt, Gondry took advantage of it and let Carrey and Winslet do some improvising of their own.
But spontaneity also permeated the planned scenes. Gondry would have two cameras going, shooting the actors from different angles, and he would just keep rolling through an entire scene, or he would shoot a scene many times in a row if the actors wanted to try different things. The cameras would simply follow them, and they were free to move around a scene, without any specific places where they had to stand… unless there were, but we'll get to that in a moment.
Gondry used this freedom to create a naturalistic feeling in the film, a sense that we're witnessing a documentary of sorts, a simple filming of real people in real-life, despite all of the science fiction and narrative oddities built into the film.
The Spotlight Mind
The use of natural lighting also contributed to this documentary feeling, whether we're talking about the use of sunlight coming in through a window or the use of other hidden practical lighting, as cinematographer Ellen Kuras talks about here. But this natural feeling changes when we get deeper into Joel's mind during the memory sequences. Especially when Joel and Clem are on the run, we get a heightened, more dramatized use of lighting.
One instance of this is the spotlight, which is representative of Joel's consciousness. At first, it seems as if that Joel's memories are massive, spanning as much space as reality. But as they are erased, Joel's awareness is confined to a small focal point surrounded by a dark void. This is most apparent in the scene where Clem is lying on the floor and is suddenly sucked away from him into the blackness.
Blocking Out Reality
And while we continue talking about the naturalism in Gondry's directing, let's not forget about some of the crazy blocking (which basically means "actors moving around," for all you non-theater geeks out there). In the scene during which Joel is chasing Clem in his apartment, Clem goes into the bathroom, and when Joel follows her in there, she has disappeared. Joel walks back to the kitchen, where he finds Clem continuing to pack up her things. Then the camera pans to the door, and Clem is somehow outside already, shutting the door behind her, leaving Joel behind.
Clem's constant disappearing and reappearing is meant to represent the erasure of this memory from Joel's mind, but it wasn't done with any clever editing. It really is all one continuous shot, just as it looks. Gondry used trapdoors to allow Kate Winslet to move quickly between set locations that appear far apart; and with the focus on Joel's perspective, the viewer can't see any of this movement.
There's also a kind of naturalism in the lack of special effects. Apart from a few scenes—for example, the scenes in which a car falls or a house crumbles—there is very little use of CGI. Even the scenes during which Joel is very small and sitting under the table or bathing in the sink are the result of optical tricks like forced perspective.