Computar CBF-1 Camera Back Focusing Neutral Density Filter w/Case

The CBF-1 Neutral Density Filter is used primarily to make the proper back focus adjustments when installing motorized zoom lenses. assure that a lens stays in throughout range, camera must be backfocused iris wide open. placed front of keep auto-iris open during adjustment. 4" x square and made glass - not plastic has an ND rating 3.0. essential tool for professional installer. Protective case included.