The ASA standard underwent a major revision in 1960 with ASA PH2.5-1960, when the method to determine film speed was refined and previously applied safety factors against under-exposure were abandoned, effectively doubling the nominal speed of many black-and-white negative films. For example, an Ilford HP3 that had been rated at 200 ASA before 1960 was labeled 400 ASA afterwards without any change to the emulsion. Similar changes were applied to the DIN system with DIN 4512:1961-10 and the BS system with BS 1380:1963 in the following years. COUNT 5
QSN1 In what year were big changes made to the ANSI? ANS1 1960 QSN2 What did the 1960 changes to film speed measures lead to? ANS2 effectively doubling the nominal speed of many black-and-white negative films QSN3 Which other system were these changes applied to? ANS3 the DIN system QSN4 In what year was the BS system modified? ANS4 1963 QSN5 What safety factors were done away with beginning with the modifications to the standards? ANS5 safety factors against under-exposure