iris-diaphragm

iris diaphragm

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.
Also called iris.


Origin:
1885–90

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World English Dictionary
iris diaphragm
 
n
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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