
The variable aperture - the iris. A new definition for 'Diaphragm Iris' is in the photography glossary.
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The light coming into your camera is controlled by the iris
The aperture size regulates the amount of light that you allow into your camera while taking a picture. However, it is the ‘Iris Diaphragm’ mechanism that controls the aperture size. It is a sophisticated mechanism in today’s cameras. In former times the diaphragm was a component of the lens in its own right. Today the iris and the diaphragm are one mechanism which together control aperture size .
The new entry in the Photographic Glossary: Diaphragm; Iris Diaphragm; Iris