<ul><li>Constant T2.9 aperture across the entire zoom range</li><li>Eliminates the need to re-focus after zooming in or out</li><li>No time lag as seen in an electrical control system</li><li>Minimizes focus shift and optical axis shift while zooming</li><li>Reduce change of angle of view during focusing</li><li>Three fully manual rings to adjust focus, zoom and iris (aperture)
  The focus ring features a rotation of a full 200 degrees to facilitate precise focusing</li></ul>