Patent Document No. 1 discloses an image input system in which a digital camera and a computer are connected together. In that system, in accordance with a command that has been received from the computer, the digital camera determines whether power should be supplied from an external power supply or a USB bus power. The computer disclosed in Patent Document No. 1 accepts the mode setting that has been specified by the user and issues a command to change the power supply sources in accordance with his or her instruction.
As a result, an image input system, with which the user can transfer image data or make remote shooting without paying attention to the level of the battery or whether the AC adapter is connected or not, is provided.
The image input system disclosed in Patent Document No. 1 changes the power supplies for the digital camera depending on which of various modes of operation, including shooting and data transfer, is now selected. In this manner, the system can avoid an unwanted situation where the battery level is excessively low or where no AC power can be supplied, and can carry on shooting, retrieving image data from a memory card, and transferring it to the computer continuously.