A Kerr cell shutter is a type of photographic shutter used for very fast shutter speeds down to nanosecond level. The Kerr Cell consists of a transparent container (A) filled with nitrobenzene (B) with attached electrodes (C and D). A high voltage is passed through the electrodes which causes an electric field perpendicular to the transmitted light beam to be applied. Its primary disadvantage was the use of toxic and flammable substances such as nitrobenzene and o-nitrotoluene. These have now largely been replaced by KTN (potassium tantalate niobate) and barium titanate (BaTiO3).