I want to take some pretty long exposures... 6-8 hours, for a project I'd like to do. Am willing to use any B&W film, but 400TX is my preference since I use a lot of it. I have no real questions to ask, but was looking for some pointers. I took some test exposures, but the room was apparently too dark, and I didn't get sh*t. Does reciprocity failure step in at some point and just end it? I can always light the room a bit more, but I'm worried about extreme overexposure... Thanks in advance for helping out with such a vague request.