iris diaphragm

American

noun

Optics, Photography.

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 British

noun

Sometimes shortened to: iris. 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

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of iris diaphragm

First recorded in 1885–90

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

The shell subunits from adjacent protomers overlap like an iris diaphragm, forming large interfaces in both TcA states.

From Nature • Apr. 4, 2014

In 1887 Edward Bausch invented the iris diaphragm shutter which made the snapshot camera practical.

From Time Magazine Archive

Stand with illuminating apparatus, swing-out condenser and cylinder iris diaphragm $60.—

From Microscopes and Accessory Apparatus Catalogue No. 40 by Leitz, Ernst

The cylinder iris diaphragm comes into play when the condenser is swung out of position.

From Microscopes and Accessory Apparatus Catalogue No. 40 by Leitz, Ernst

The condenser and iris diaphragm form one piece, giving central but no oblique illumination.

From Microscopes and Accessory Apparatus Catalogue No. 40 by Leitz, Ernst

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023