For normal use, I essentially never expose anything outside of color transparency film at the manufacturer's stated ISO. I have found that I essentially cannot get an ideal negative out of a negative film at the stated ISO. Tri-X gets rated at 200, Bergger at 100, HP5 at 250, NPS at 100. You get the idea. Learning this was one of those things that did more to improve the technical quality of my images than most other things. For a long, long time I always shot at the stated ISO and not an EI that I arrived at myself through testing. Looking back, those negatives are thin and lack shadow detail.