A projector with a dynamic iris uses a mechanical iris to adjust the amount of light passing through the projector's lens. The dynamic iris works by changing the size of the aperture in real-time, depending on the projected image's brightness. It can provide several benefits, such as improving the projector's contrast ratio, reducing the projector's power consumption, and reducing the projector's fan noise. Not all projectors have a dynamic iris. It's not a standard feature in most projectors, but it's a feature in some high-end projectors.