The Formatt-Hitech 85 x 85mm Firecrest ND 2.1 to 3.0 Filter Kit contains 4 Firecrest ND filters, ranging in density from 2.1 to 3.0 to provide a reduction in exposure from 7 to 10 stops. By darkening the entire image, you can photograph with a wider aperture or slower shutter speed than normally required for greater control over focus, movement, and brightness.
The design of these filters has been optimized for use with digital sensors and promote nearly flat attenuation of visible, UV, and infrared light. Due to imaging sensors' greater susceptibility to infrared light, compared to traditional film, color casts can occur when photographing darker subjects that require increased exposure times. These filters provide a high level of neutrality across all three spectrums in order to eliminate color casts and ensure cleaner, truer blacks.
Applied to the outside of the Schott Superwite glass construction is a 15-layer Firecrest multi-coating, which helps to minimize reflections and flare in order maintain truer colors and contrast. The multi-coating is also scratch-resistant and hydrophobic to benefit the overall durability of the filters. Each filter in this kit measures 3.3 x 3.3" / 85 x 85mm and is 0.08" / 2mm-thick, making it compatible with the Formatt-Hitech 85mm Filter Holder.