Metric thread (8mm diameter) standard on European lighting accessories—barn doors, color filters, diffusers. Established by Arri and Dedolight since the 1970s.
Technical Details
M8 threads have a core hole diameter of 6.8mm and a thread depth of 0.613mm. The maximum load capacity for steel of strength class 8.8 is approximately 1,200N tensile force. Standard M8 screws have head widths of 13mm (hexagonal) or 6mm (internal hex). In film technology, stainless steel or anodized aluminum versions are predominantly used to prevent corrosion and reflections. Typical screw lengths range from 12mm to 50mm, with 16mm, 20mm, and 25mm being the most common variants.
History & Development
The M8 thread established itself in European film technology from the 1970s onwards as an alternative to British Whitworth threads and American UNC standards. Arri consistently introduced M8 for the first time in 1978 with the L-series Fresnel lights. In the 1990s, M8 was standardized by the European Broadcasting Union (EBU) as a recommendation for lighting accessories. Today, all major European manufacturers such as Arri, Dedolight, and K5600 use M8 as their primary mounting standard.
Practical Application in Film
M8 mounts are found on barndoors, color filter frames, diffusers, and reflector holders. In "Blade Runner 2049," DoP Roger Deakins used M8-based modifications on Arri SkyPanels to achieve precise light shaping. Standard workflows utilize M8 quick-release fasteners for efficient changing of accessories during shooting. Compatibility between different manufacturers allows for universal accessory use, but improper mounting can reduce the durability of aluminum threads in luminaire housings.
Comparison & Alternatives
M8 differs from the smaller M6 (6mm diameter, 1.0mm pitch) by having a higher load capacity, and from the M10 by having a lower weight while providing sufficient strength. American productions often use 5/16"-18 UNC threads, which have similar dimensions but a different pitch. Modern quick-release systems such as Chimera Speed Ring or Dedolight DLOBML are increasingly replacing classic M8 screw connections with tool-free bayonet or clamp connections for accelerated set-up.