In an increasingly digital era, it's easy to lose sight of film's long history as a deeply material art form. Film is projected light, the chemistry of emulsions and developers, silver nitrate colloids and dichromate bleach, the mechanics of film reels in motion. The filmed image is a true imprint of reality, a kind of ghost with an expressive power held by few media. Once it was considered a machine for generating emotion, nowadays it helps us to understand how the brain processes visual information. This issue pays homage to the medium of film itself, not only its origins and classical techniques for fixing images of the world, but to present developments, changing technologies, and future applications. As one of our youngest art forms, it remains be one our most dynamic: this multifaceted portrait of film up to 2019 is a but a snapshot of a system ever in transition.