The photo of mountain gorillas (above) is a case in point. These animals live high in the mountains in Uganda's impenetrable forest. Getting to them often requires a long and difficult trek in very hot, humid, and sometimes rainy conditions. Once you find the gorillas, you'll have only one hour to spend with them. These primates move about as they wish, in and out of the dense bush, under constantly changing light. So, to photograph them, you need to travel as light as possible, and to be able to work fast in difficult conditions.