The Formatt Hot Mirror filter has been designed to correct Infrared pollution.
Unlike film cameras, digital cameras are sensitive to Infrared light. This becomes more noticeable when using neutral density filters especially when higher densities are used, as is now often the case with many (particularly top end) digital cameras.
The Formatt Hot Mirror filter has a sharp cut-off at Infrared wavelengths but will not interfere with the visible red wavelengths. The Hot Mirror coating is sandwiched internally to eliminate any possibility of damage to the coated surface.
Please note that lead times are currently two weeks.