Polarising, neutral density, conversion, diffusion and effects filters (for example Blue Streak 4×5.650 and Mitomo True ND/IRND 4×5.650 sets, full and split dioptres)
Example: Mitomo TRUE ND neutral density filters, whose clear glass carries a deposited metal alloy layer on each face; transmission stays flat up to 750 nm, so infrared is filtered too. 4×5.65 format, densities 0.3 to 2.4.