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

Example Sentences

Rack the condenser down slightly and cut down the aperture of the iris diaphragm so that the light, although even, is dim.

From Project Gutenberg

They are also fitted with indicator for registering each exposure as made and iris diaphragm.

From Project Gutenberg

The simplest way of achieving this is by means of what is called an iris diaphragm.

From Project Gutenberg

To illustrate the functions of the iris diaphragm we will take the Williamson instrument.

From Project Gutenberg

By the aid of the iris diaphragm the diameter of the aperture may be varied from approximately ⅗ to ⅛ of an inch.

From Project Gutenberg