Multi-layer anti-reflective coating of magnesium fluoride, titanium oxide, and silicon oxide achieving 99.7–99.9% light transmission and eliminating ghosting.
Technical Details
HMC Coating consists of alternating layers of magnesium fluoride (MgF₂), titanium oxide (TiO₂), and silicon oxide (SiO₂) with refractive indices between 1.38 and 2.35. The outermost layer has a hardness of 6-7 on the Mohs scale and withstands mechanical stress up to 200 Newtons per square centimeter. Modern HMC systems transmit 99.7-99.9% of incident light in the spectral range of 400-700 nanometers. Special variants like Nano Crystal Coating (Nikon) or ASC (Canon) additionally integrate crystalline nanostructures that maintain reflections below 0.1% even at extreme angles of incidence above 60°.
History & Development
Zeiss introduced the first single-layer coating with magnesium fluoride in 1935. Canon developed the first practical HMC coating for their FD lenses in 1971, achieving transmission values of 98.5%. Nikon followed in 1977 with Integrated Coating (IC), which was specifically optimized for their AI lenses. From 1995 onwards, electron beam evaporation systems enabled the production of up to 15-layer coatings with tolerances below 2 nanometers. Since 2010, plasma-assisted processes have dominated, which also integrate organic polymer layers and achieve transmission values of 99.9%.
Practical Use in Film
For "Blade Runner" (1982), Ridley Scott exclusively used HMC-coated Zeiss lenses to avoid ghosting in complex night shots with multiple light sources. Roger Deakins consistently relies on modern HMC coatings for backlight shots, as demonstrated in the desert sequences of "Sicario" (2015). The coating enables contrast ratios of over 2000:1 without stray light artifacts. HMC coating is standard in IMAX productions, as the large sensor areas are particularly susceptible to reflections between the lens and protective glass. Digital Intermediate Colorists report 15-20% less effort in artifact removal for HMC-coated footage.
Comparison & Alternatives
Simple MC coatings (3-5 layers) only achieve 97-98% transmission and fail with LED light sources having narrow-band spectra. Pentax's Super Multi Coating (SMC) uses 11 layers and achieves similar values to HMC but focuses more on the UV range below 400nm. Modern nano-coatings like Fujifilm's EBC or Sigma's DG DN surpass classic HMC systems with hydrophobic properties and self-cleaning surfaces. For available light and low-key situations, HMC coating remains indispensable, while MC coatings can provide sufficient results in controlled studio conditions.