Which lens type responds to changes in light levels but does not adjust based on focus?

The correct answer is the DC-Iris Lens. This type of lens is designed to automatically adjust the aperture based on ambient light conditions. It effectively regulates the amount of light entering the camera, ensuring optimal exposure under varying lighting scenarios. The DC-Iris Lens does this without changing its focus, meaning it maintains a fixed focal length while responding to light level changes. This is particularly valuable in environments where lighting can fluctuate, as it prevents overexposed or underexposed images.

Other lens types, such as autofocus or manual iris lenses, may offer different features, such as focus adjustments or manual control over the aperture, but they do not specifically operate solely on light level changes like the DC-Iris Lens does. A fixed iris lens, on the other hand, has a constant aperture and does not adjust to changing light conditions at all. Thus, the unique functionality of the DC-Iris Lens in adjusting to light changes while maintaining focus makes it the right choice for this question.