the high cost of the film, processing and printing, the mediocre color quality, rapid fading and discoloration of highlights of some types of print that became noticeable after several years. Amateurs who owned projection equipment used reversal films extensively because the cost of projection equipment and slide film was offset by not having to pay for prints. Eventually, print quality improved and prices decreased, and, by the 1970s, color negative film and color prints had largely displaced slides as the primary method of amateur photography. Until about 1995, color transparency was preferred for publication because of the films' higher contrast and resolution, and was widely used in commercial and advertising photography, reportage, sports, stock and nature photography. Digital media gradually replaced transparency film. Film types All color reversal film sold today is developed with the E-6 process. The non-substantive Kodachrome films, the last of which was discontinued in 2009, were processed with the K-14 process. Polaroid produced an instant slide film called Polachrome. It was packaged in cassettes like normal 35mm film. A separate processing unit was used to develop it after exposure. Black and white Black-and-white transparencies can be made directly with some modern black-and-white films, which normally yield negatives. The negative image is developed but not fixed. The negative image is removed by bleaching with a solution of potassium permanganate or potassium dichromate in dilute sulfuric acid, which is removed by washing and a clearing bath containing sodium metabisulfite or potassium metabisulfite. The remaining silver halide salts are re-exposed to light, developed and fixed, and the film is washed and dried. Black-and-white transparencies were once popular for presentation of lecture materials using 3¼"×4" (3¼" square in the UK) glass-mounted slides. Such positive black-and-white projection is now rarely done, except in motion pictures. Even where black-and-white positives are currently used, the process to create them typically uses an internegative with standard processing instead of a chemical reversal process. Black-and-white reversal films are less common than color reversal films. Agfa-Gevaert discontinued its Agfa Scala 200x Professional black-and-white reversal film. This could be developed with their proprietary Scala process. The Adox company released Scala 160 In 2017 , A black and white reversal film based on Agfa's discontinued Scala. The Foma company of the Czech Republic produces one of only remaining dedicated black-and-white reversal film for 35 mm stills, Fomapan R 100, which is also available in movie film formats. Kodak