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

The shutter leaves are formed of segments opening in star shape, giving even illumination over the entire plate the instant the exposure is started, and it has an iris diaphragm.

From Premo Cameras 1914 by Canadian Kodak Company

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

From The Elements of Bacteriological Technique A Laboratory Guide for Medical, Dental, and Technical Students. Second Edition Rewritten and Enlarged. by Eyre, J. W. H. (John William Henry)

Tycho Brahe invented, and applied to the pointers of his instruments, an aperture-sight of variable area, like the iris diaphragm used now in photography.

From History of Astronomy by Forbes, George