A diaphragm device in the lens that adjusts to light level changes. The iris diaphragm opens or closes the aperture to control the amount of lights coming through the lens.

A lens that automatically adjusts to allow the correct amount of light to fall on the imaging device. There are a tiny motor and amplifier built in which generally receives a control signal from the c [..]

lens diaphragm which is controlled by a mechanism in the camera body coupled to the shutter release.