What characteristic defines a Fixed Iris Lens?

A Fixed Iris Lens is characterized by having a set iris opening size that remains constant and cannot be adjusted. This means that once the lens is manufactured, the aperture size is determined and does not change regardless of varying light conditions. The fixed iris allows for consistent exposure settings, which can be beneficial in controlled environments where lighting does not fluctuate.

In contrast, an adjustable iris opening size is found in lenses that allow users to modify the aperture to either widen or narrow the amount of light entering the lens. Lenses that automatically adjust to light levels will change their aperture depending on the lighting conditions, which is not a feature of a fixed iris. Similarly, the ability to memorize focus settings pertains to focus mechanisms, not iris functionality. The key aspect of the fixed iris is its unchanging aperture, ensuring reliability in specific lighting situations.