So if anyone's seen the most recent zombie movie 28 Weeks Later you'll notice some hella awesome day for night scenes. TOTALLY RAD' and BEAUTIFUL!
I understand the basic idea of underexposing to make things darker (or blue filter and polarizer when shooting color) but I'm wondering if there might be more of a technique than just underexposure. e.g. does it make more sense to expose normally and under develop (maybe n-2) or to under expose and develop normally? etc.