At the Milwaukee County Zoo, the small mammals building has two sides separated by a wall. Side one has diurnal animals and side two has nocturnal and crepuscular animals. Side one is well-lit and I have no problems photographing there. Side two is only barely lit and I have immense difficulty seeing, let along shooting.
Obviously, flash photography is prohibited on the Dark Side. How would you like it if your ƒ/1.2 dark-adapted eyes were suddenly blinded by an intense flash? The obvious answer is a longer exposure. Which works great if the subject of your photograph stands still for any length of time. But small mammals rarely stand still unless they’re asleep. Right now, the best I can do is use my camera’s builtin lighting optimizer, a wide-open aperture (well, ƒ/2 on an ƒ/1.4 50mm prime – anything less and the lens goes soft), the longest shutter speed that still works (1/60s) and an absurdly high ISO speed (3200). An APS-C sensor at 12MP should be able to collect enough light that the above-average grain level of ISO 3200 won’t look terrible once I adjust the exposure settings in darktable.
There was a semi-pro armed with Canon gear who was also shooting in the dark. I asked him for advice and he said “5D, 70-200mm f/2.8L, monopod.” Which is great advice, provided you have a spare $8,000 to spend on a hobby. In other words, rather than improving my skill or using my brain, I should just spend more money. I really don’t care for that attitude at all. FTR, I have a monopod but I wasn’t using it that day in the interests of saving time. If I had a few hours to spend watching a single subject, then I’d deploy that.