I'm familiar with 400 TMAX, and so I know that it can handle a bit of overexposure gracefully, and it works very comfortably at EI 250. Medium Format means you will not notice grain as much as if you were shooting 35mm. If you were to take a 100 speed film, you could get some amazing fine-grain photographs, but will you use a tripod? Otherwise you might hand-hold, like I do. I get better handheld photographs on EI 250.