This is a Graduated Neutral Density Filter used for Cinematography. 50% of the filter is clear and 50% has a Neutral Density of 1.2 (4 stops). The transition from clear to ND is done with a SOFT EDGE (SE) transition line. SOFT EDGE grads lines are used with wide angle and normal focal length lenses.
Graduated Neutral Density filters are used to balance exposure within a scene. One very common use is to balance the exposure of sky and earth in a landscape, avoiding overexposed blank white skies.
The Schneider Group specializes in developing and producing high-Performance lenses for film and photo, cinema projection lenses, as well as industrial optics and precision mechanics. 1913 founded in Bad Kreuznach, Germany, as a mechanical shop for optical lenses, Jos. Schneider Optische Werke GmbH is today a worldwide market leader in high-quality lenses and precision engineering.