I would say n+2 is easy to get, but no more. You start getting very high b+f. I have calibrated by the BTZS method, but in zone speak a SBR of 6 is similar to a "n+2" situation. I gotta tell you, is a nice film but I did not see an advantage over TMX to spend the extra money on it. Reciprocity for TMX 400 is not bad, and I rarely shoot at more than 3 or 4 seconds, so the only advantage ACROS would have does not justify the extra expense. My experience, dont bother buying it.