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.

---

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

---

Etymology

Origin of iris diaphragm

First recorded in 1885–90

Example Sentences

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

The small illuminating apparatus consists of a somewhat smaller condenser with iris diaphragm and can be adjusted to the Stand IV, when it has the cylinder diaphragm.

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

It is fitted with iris diaphragm and supplied with the Nos.

From Kodaks and Kodak Supplies 1914 by Canadian Kodak Company

A ring under the iris diaphragm serves to hold a ground glass or colored disc.

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