Hello: A number of the professional film data sheets Fujifilm sent me said no reciprocity correction needed up to 120 seconds...I was as surprised by that as I was by the steep exponential curve once you hit the reciprocity failure region...the multipliers were so high it seems things would be very non critical once you were in the ballpark.
Ilford B/W web data had pretty steep curves for reciprocity correction too. Murray
