The subject here is drawn from nothing: a set of overlapping radial fields that suggest a skull, a jaw, two eyes and the shadow of a nose, all of them soft ellipses in space. Twelve thousand points are scattered across the frame and each one is sized by how much light reaches it.
That is the whole trick of pointillism, and it is also how a printed halftone works — a photograph reduced to a grid of dots whose size encodes the local brightness. Move the light and the whole face changes, because the picture was never in the dots.