Variable ND

Technical Details

Variable ND filters typically achieve density values from ND 0.3 to ND 3.0 (equivalent to 1-10 stops). High-quality models like the Tiffen Variable ND or PolarPro Peter McKinnon Edition use multi-coated lenses with 16-20 coatings. At maximum darkening, characteristic cross-shadows (X-pattern) appear due to the crossed polarization axes. The filters are available in diameters from 52mm to 82mm; professional matte box systems use 4x4" or 4x5.65" variants.

History & Development

Singh-Ray developed the first commercial variable ND filter for photography in 1999. Tiffen adapted the concept for film productions in 2008 with the Variable ND. The breakthrough came in 2012 with RED cameras, whose high light sensitivity made variable NDs indispensable for daylight shooting. Modern versions like the B+W XS-Pro (2018) reduce color casts and vignetting through precise polarization film adjustment.

Practical Use in Film

Variable NDs allow for quick exposure adjustments in handheld shots without changing filters. "Mad Max: Fury Road" (2015) used them for continuous drives between shadow and sunlight. For interviews, they allow spontaneous aperture changes without interruption. Documentarians appreciate the flexibility in changing light conditions. Their use becomes problematic with wide-angle lenses below 35mm, where vignetting and X-pattern artifacts become visible.

Comparison & Alternatives

Fixed ND filters (ND 0.6, 1.2, 1.8) offer higher optical quality without polarization effects but require filter changes. Electronic ND filters in cameras like the Sony FX9 (ND 0.6-2.4) work without artifacts but are limited to camera-internal ranges. IRND filters combine infrared protection with neutral density, while variable NDs primarily operate in the visible spectrum. For controlled studio conditions, fixed filters remain standard; variable versions dominate documentary and run-and-gun productions.