A device for switching optical filters of a camera constantly provides clear images during the day and night. A lens (1a) mounted on a camera body (1) forms an image on an imaging device (2), which in turn converts the image into an electric signal to obtain an image signal. Means (3) for switching optical filters (3a, 3b) depending on the level of the image signal is provided in front of the imaging device (2). The camera can be advantageously used in a monitoring system to improve reliability since it provides clear images during the day and night.