I want to know the answer to the following question:
What happened to film speeds of black-and-white negative film?
All the background I'm provided with is that "This revision also saw significant changes in the definition of film speeds in order to accommodate then-recent changes in the American ASA PH2.5-1960 standard, so that film speeds of black-and-white negative film effectively would become doubled, that is, a film previously marked as "18° DIN" would now be labeled as "21 DIN" without emulsion changes.". Is that enough to answer the question?
Answer: yes