Definition of orthochromatism in US English:

orthochromatism

noun

Photography
rare
  • The condition of being orthochromatic.

Origin

Late 19th century. From orthochromat- + -ism. Compare French orthochromatisme.

Pronunciation

orthochromatism

/ˌɔːθəʊˈkrəʊmətɪz(ə)m/