I took an early morning trip to our nearby butterfly house this morning. They open the doors an hour early for photographers on the first Saturday and Sunday of the month, during the season. I like that first hour because the fans and heaters aren't yet going full blast, so the butterflies are still a bit sleepy. I am pretty happy with the shots I took (link below). All are taken hand-held at 1/250 second and (usually) F8. Mostly ISO at 1600, with a few at ISO 800. My camera settings: Manual mode set at my desired shutter speed and F-stop, and auto ISO. All are with natural light, diffused somewhat through the glass dome of the butterfly house.