Context: 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.

Question: In what year were big changes made to the ANSI?
Answer: 1960

Question: What did the 1960 changes to film speed measures lead to?
Answer: effectively doubling the nominal speed of many black-and-white negative films

Question: Which other system were these changes applied to?
Answer: the DIN system

Question: In what year was the BS system modified?
Answer: 1963

Question: What safety factors were done away with beginning with the modifications to the standards?
Answer: safety factors against under-exposure

Question: When were new safety factors put in place?
Answer: Unanswerable

Question: The nominal speed of what films were halved by abandoning safety factors?
Answer: Unanswerable

Question: A 400 ASA became what after 1960?
Answer: Unanswerable

Question: When were changes applied to the DIN system?
Answer: Unanswerable

Question: The Ilford HP3 changes were applied to what in the following years?
Answer: Unanswerable