Neutral density filter built into the camera body, electronically engaged to reduce light intake without swapping lenses.
Technical Details
Modern cinema cameras like the ARRI Alexa 35 feature internal ND filters with values of 0.6 ND (2 stops), 1.2 ND (4 stops), and 2.1 ND (7 stops). The RED V-Raptor offers 1, 2, 3, 4, 5, and 6 stops of reduction. Sony FX9 and Canon C500 Mark II utilize variable internal ND systems with stepless adjustment from 0.6 to 2.4 ND. The filters are made of multi-layer coated optical glass mounted on precise servo mechanisms. Electronic sensors ensure exact positioning with an accuracy of ±0.1 stops.
History & Development
Panasonic introduced the first internal ND filters in semi-professional cameras with the HVX200 in 2006. Sony established the system in PMW series broadcast cameras in 2012. ARRI first integrated internal ND filters into the Alexa SXT in 2017, followed by RED with the Komodo in 2019. Canon revolutionized the concept in 2020 with the first stepless internal ND system in the C500 Mark II. Current developments focus on extended filter ranges up to 10 stops and improved coatings to minimize infrared pollution.
Practical Use in Film
For "Dune" (2021), DoP Greig Fraser used internal ND filters on the ARRI Alexa LF for seamless exposure adjustments during desert pans. "The Batman" (2022) relied on the Canon C500 Mark II with its stepless internal ND for smooth day-to-night transitions. Internal ND filters allow for a constant aperture of f/2.8 under varying daylight conditions without changing lenses. Documentarians appreciate the rapid response time of under 0.2 seconds when lighting conditions change.
Comparison & Alternatives
External matte box filters offer a wider variety of filters (up to 15 stops) but require manual operation and additional equipment. Variable external ND filters often exhibit color shifts and cross-polarization, whereas internal systems remain color-stable. Electronic ND filters in high-end broadcast cameras achieve up to 20 stops but cost three times as much. For extreme filter values above 8 stops, external solutions remain indispensable as internal systems are inherently limited by design.