This image was taken in Gunung Mulu National Park, Sarawak, Borneo in 1999. The national park boasts a series of massive caves, including the Sarawak Chamber, the largest single cave chamber in the world. Deer Cave, in addition to being huge, with an entrance 100 metres wide, is notable for it bats. The cave contains millions of them, 12 different species have been observed there including an estimated 3 million wrinkle lipped bats making this one of the largest bat colonies anywhere in the world.
Each evening the bats fly out of the cave setting out over the surrounding jungle to feed on flying insects. It's estimated that each bat will consume 5 to 10 grams of insects each night, so collectively consuming several tonnes each night. The number of bats is such that it takes over an hour for them to clear the cave, the spectacle resembling a column of smoke rising up from a fire before stretching out over the treetops.
This image was taken using a Pentax MEF 35 mm SLR with a 80-400mm zoom lens and Kodak ISO 100 colour negative film. Aperture and shutter speed were not recorded, but given that I was using slow film towards the end of the day with light levels falling, it's safe to say the aperture was wide, probably F5.6, so as to allow the fastest possible shutter speed. A slow shutter speed of course would have rendered the bats as a blur given their movement.
The negative was scanned using the Epson V700 faltbed scanner and Epsonscan software. The image is presented here full frame and contrast was increased slightly in Photoshop so that the bats stand out against the darkening sky.