GELATIN Neutral Density Filters can be used in image forming optical systems to reduce light intensity in the visible spectrum without changing the spectral profile.
Gelatin Neutral Density Filters transmit the infrared spectrum, neutrality is controlled only in the visible spectrum. All ND filters are 0.1mm in thickness.
Gelatin Filters offer a low cost solution compared to glass ND filters
Please see below for Optical Density / transmission values