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Glossary: Auto Iris Lens

Lenses with iris widths

The Iris is a component in a camera lens which can be opened or closed to let in more or less light to the imaging sensor. This helps balance the exposure of the image so that the camera can provide a high quality image, ideal for security applications which require fine detail such as being able to recognise faces or objects.

In a large security surveillance and monitoring system it is not realistic to expect the operator to manually adjust the iris of each camera according to lighting conditions, especially if they have a large number of cameras or for cameras which are located outdoors. Using a camera which includes an auto iris lens provides a solution. The camera will detect the amount of light entering the lens and automatically open or close the iris to provide an image of the correct exposure.

Outdoor use

Cameras with auto-iris lenses are recommended for outdoor use as light can change dramatically throughout the course of the day, especially if the sun is prominent in the image to be captured.


Some fixed cameras come with manual iris lenses which can only be set on the lens once before the camera is installed. These cameras usually have routines and settings in the software to help adjust the exposure.

Published on August 15th, 2008 by Greg

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