Chipmunk Camera Vibration/ASA
BEagle
We tended to use 400ASA B/W film mostly, with occasional 400ASA Ektachrome for colour if the colour added more int to the target. Because both the 500 and the 1000mm mirror lenses had fixed apertures, the only control available was either shutter speed or pushing the ASA. On the ground, even in the summer, using the 1000mm handheld against the underneath of aircraft, it was necessary to find your own personal minimum shutter speed, which came with lots of practise. Mine was 250th, so the ASA had to be pushed to match that - normally from 800 ASA up to 6400ASA in the grey days of winter - unless the snow on the ground gave a reflective helping hand. In the aircraft, the same applied, although 500th was my minimum, making sure you never touched the cockpit surrounds. In later years (after 1988ish) the Mission changed generally to 400ASA colour print, but the analysts tended to prefer B/W for getting into details.