This bizarre and wonderful little dance film is made by Adrien M / Claire B using a slit scan technique which I guess you can compare to how a scanner captures a picture. The camera captures one “stripe” of the image at the time, with a delay of a certain amount of time for the next stripe, quite like moving something (paper/hand/face/props) over the surface at the same time as the scanning happens, you will get a warped image of what you scanned. An explanation from the comment section for the video reads like this:

It’s done with a Quartz Composer patch we have developed that will be public in two or three month.
The idea is very simple : the first line of the video is realtime, the second line is late of 1/60s, the third is late of 2/60s, etc.It’s like a very long rolling shutter

Wikipedia has a more technical (and pop cultural) explanation of the technique:

-An abstract colored design is painted on a transparent support.
-This support is set down on the glass of a backlighting table and covered with an opaque masking into which one or more slits have been carved.
-The camera (placed high on top of a vertical ramp and decentered in relation to the light slits) takes a single photograph while moving down the ramp. The result: at the top of the ramp, when it is far away, the camera takes a rather precise picture of the light slit. This image gets progressively bigger and eventually shifts itself out of the frame. This produces a light trail, which meets up with the edge of the screen.
-These steps are repeated for each image, lightly peeling back the masking, which at the same time produces variation in colors as well as variation of the position of the light stream, thus creating the animation.

Originally used in static photography to achieve blurriness or deformity, the slit-scan technique was perfected for the creation of spectacular animations. It enables the cinematographer to create a psychedelic flow of colors. Though this type of effect is now often created through computer animation, slit-scan is a mechanical technique. It was adapted for film by Douglas Trumbull during the production of Stanley Kubrick’s 2001: A Space Odyssey (1968) and used extensively in the “stargate” sequence. It requires an imposing machine, capable of moving the camera and its support.

Via The Curious Brain and Colossal.

/Mari