What is the functionality of Autofocus in a lens?

Autofocus in a lens refers to its ability to automatically adjust the focusing mechanism to ensure that the subject of the image is sharp and clear as the scene changes. This feature is essential for capturing moving subjects or scenes where the distance between the camera and the subject may vary rapidly, allowing photographers to maintain focus without needing to manually adjust the lens.

For instance, in fast-paced photography environments, such as sports or wildlife photography, having the autofocus capability allows the camera to track subjects effectively, which is crucial for capturing moments accurately. The lens uses various sensors and algorithms to assess the distance to the subject, continuously making adjustments to the focus in real-time.

The other choices do not accurately describe the primary function of autofocus. Memorizing and recalling focus settings is more relevant to manual focus techniques or specific settings in digital cameras, whereas fixing the lens opening size pertains to aperture control, and requiring manual adjustments for focus directly contradicts the core purpose of autofocus technology. Thus, the answer highlighting automatic focus adjustment as scenes change captures the essence of what autofocus offers in a lens.