Efke films are manufactured using classic emulsions with very high silver content. This results in a large exposure latitude and superior grayscale reproduction. The Efke 25, 50 and 100 films are made using the ADOX formulas that were first introduced back in the 1950s. Efke products are true to their rated speed. Unlike modern flat crystal films, which are very unforgiving to use, these films allow beginners to produce quality images. The nature of the film also easily allows large, grain free, enlargements to be made from negatives. Do NOT over-expose Efke Emulsions! This film is not recommended for pull processing. Treat the wet emulsion with extreme care. We recommend the use of hardener in the stop bath or fixer. Never use a stop-bath with a higher concentration than 2% -- in fact, we recommend the use of plain water in place of a stop bath. Efke roll films (KB) are coated on an acetate base. If exposed to film's regular speed of ISO 400, the following developing times apply: Kodak D76/ID-11 = 7.5 Minutes If ISO 400 film is exposed to ISO 800 for increased speed and optimum differentiation of highlights, the following developing times apply: Kodak D76/ID-11 = 10.5 minutes. Made in Croatia