The hitech 77mm joel tjintjelaar signature edition kit is made up of a long exposure technique booklet long exposure conversion chart and three 77mm circular prostop infrared nd filters each with a different density 3 6 and 10 stops the hitech irnd filters reduce the amount of visible and infrared light from reaching the sensor to allow more control over depth of field and shutter speeds nd filters are heavily used by landscape photographers because it allows them to use longer exposures t