low intensity RLF

I understand that most b/w films start to suffer from this when the light intensity becomes low enough to suggest a 1 sec (or longer) exposure time. I believe though, with an unevenly lit scence, shadow areas may be experiencing this at exposures times shorter than 1sec - and therefore record with less density than they would if, overall, the light intesntiy was higher. Are we just accustomed to seeing low-intensity RLF in our negs without even realising it's presence? I think this is something more lilkey to be noticed by large or medium format users - where tripod use and low intensity/long exposures are a part of normal working. I 'd particularly like to hear from this user group who have used a 'normal' black and white film and compared with Fuji Acros 100 (which has minimal LI RLF characteristics).