Tiffen W77IRND18 77mm Filter with Combination Neutral Density (ND) 1.8 Infrared (IR), Reduces ISO to 1/64 High quality filter to prevent the color shift caused by the sensitivity of today's digital sensors Tiffen filters are manufactured using ColorCore technology, a closely guarded proprietary process that entails permanently laminating the filter material in between two pieces of optical glass that are ground flat to tolerances of a 10,000th of an inch, then mounting them in precision metal rings The ColorCore process allows Tiffen to control the color and density of their filters and the characteristics of special effects filters with much greater accuracy than typical dyed-in-the-mass filters, which usually exhibit color and density variations Natural Density Filters enables slow shutter speeds to be used, especially with high speed films, to record movement in subjects such as waterfalls, clouds, or cars Natural Density Filters decreases depth of field by allowing wider apertures to be used, which helps separate subjects from their background