Shading the lower portion of a light source using barn doors or flags to prevent unwanted reflections on the floor or lower frame area.
Technical Details
Bottom chop is primarily achieved using 4-leaf barndoors with a bottom leaf measuring 15-25 cm in length, or specialized bottom choppers with beam angles between 30° and 90°. Modern LED panels utilize digital zone control with up to 16 individually controllable segments for more precise bottom chop effects. Flag-based systems employ black silks in standard sizes from 24"x36" to 48"x48", positioned 0.5-2 meters from the light source. HMI lights from 1.2 kW upwards require heat-resistant aluminum barndoors with a temperature resistance of up to 200°C.
History & Development
The technique evolved in the 1940s in Hollywood studios, where cinematographer Gregg Toland systematically used barndoors for selective light control. In 1952, Mole-Richardson introduced the first standardized bottom choppers for studio lights. The digital revolution brought programmable LED arrays in 2010 with pixel-level bottom chop control. Modern systems like the Arri SkyPanel have offered software-based beam-shaping functions with 256 brightness levels per zone since 2015.
Practical Application in Film
Roger Deakins extensively used bottom chop in "Blade Runner 2049" for the neon scenes, to eliminate floor reflections and enhance the floating atmosphere. Emmanuel Lubezki employed the technique in "The Revenant" to simulate natural daylight without casting distracting shadows on snow. In dialogue scenes, bottom chop prevents unnatural illumination of tabletops and directs attention to faces. Night scenes benefit from reduced floor reflection and increased contrast between characters and the background.
Comparison & Alternatives
Top chop eliminates upper light components, while side chop controls lateral spill – bottom chop exclusively focuses on the lower image areas. Modern alternatives include projection lights with gobo masks or DMX-controlled LED matrices with individual pixel control. Fresnel lenses offer natural bottom chop characteristics through focusing, but do not achieve the precision of mechanical systems. Soft bottom chop using diffusion gels creates more gradual transitions, while hard barndoors produce sharp cut-off edges.