IRIS

In the camera, IRIS refers to the aperture. Iris is an important factor in determining depth, which improves image quality and depth so that you can see both distant and near objects clearly.

Aperture (from Wikipedia)

The aperture sometimes called the diaphragm or iris, is the opening through which light enters the camera. Typically located in the lens, this opening can be widened or narrowed to control the amount of light that strikes the film. The aperture is controlled by the movements of overlapping plates or blades that rotate together and apart to shrink and expand the hole at the center. The diameter of the aperture can be set manually, typically by adjusting a dial on the camera body or lens or automatically based on calculations influenced by an internal light meter.

for more information on Aperture and Camera, please visit the site below;

https://en.wikipedia.org/wiki/Camera#Aperture