iris diaphragm

noun

, Optics, Photography.

1. a composite diaphragm with a central aperture readily adjustable for size, used to regulate the amount of light admitted to a lens or optical system.

iris diaphragm

noun

1. an adjustable diaphragm that regulates the amount of light entering an optical instrument, esp a camera. It usually consists of a number of thin metal leaves arranged so that they open out into an approximately circular aperture Sometimes shortened toiris

Word History and Origins

Origin of iris diaphragm¹

First recorded in 1885–90