Definition of film speed in US English:

film speed

noun

  • 1Photography. The degree of light sensitivity of a photographic film; a numerical measure of this. In later use also: a numerical measure of the signal gain of the photosensor in a digital camera.

  • 2Cinematography. The speed at which a cinematographic film passes through a camera or projector.

Origin

Late 19th century. From film + speed.

Pronunciation

film speed

/ˈfɪlm spiːd/