iris diaphragm

American  

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.

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iris diaphragm British  

noun

1. 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

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Etymology

Origin of iris diaphragm

First recorded in 1885–90

Example Sentences

See Examples For:

iris diaphragm

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

A ring below the iris diaphragm permits the insertion of glass discs for the purpose of modifying the light.

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

In the lower power objectives the angular aperture is to be reduced by the iris diaphragm.

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