What is a common feature of both DC-Iris and Video-Iris lenses?

The correct answer highlights a fundamental feature shared by both DC-Iris and Video-Iris lenses: their ability to convert analog signals into control signals to regulate the aperture. This is important because it enables automatic exposure control, allowing both types of lenses to adapt to varying lighting conditions efficiently.

In the case of DC-Iris lenses, the lens utilizes a direct current signal to manage the aperture size automatically, responding to changes in light intensity. Video-Iris lenses, while they may use a similar mechanism, typically operate within a video system to ensure optimal exposure for image clarity during recording. This capability is crucial for applications like surveillance and broadcasting, where lighting can change rapidly.

Adjustable iris sizes, fixed focal lengths, and manual adjustments do not accurately represent the primary feature shared by both lens types, as the main advantage lies in their automatic functionality related to control signals.