The Dynax/Maxxum 5D camera sensitivity can be set to Auto, ISO 100, 200, 400, 800, 1600 and 3200 equivalent.
When Auto is selected, the camera automatically controls the sensitivity range as follows,
P, A, S modes: ISO 100-400
M mode: fixed at ISO 100
Auto recording mode: ISO 100-800(*)
Digital subject program: the camera sensitivity complies with the settings of the selected scene.
(*) Camera sensitivity range is set to from ISO100 to ISO400 when flash is fired.