To provide a photoelectric converting apparatus and system capable of adjusting the luminous quantity of an LCD backlight and a key light depending on the surrounding lightness so as to enhance the visibility, save power, and extend the lifetime of light emitting elements.

The photoelectric converting apparatus and system is provided with: an operation key 3 used to enter instructions; the key light 5 placed under the operation key 3; an LCD 2 for displaying the instruction entered by the operation key 3; an optical sensor 1 provided with a plurality of photoelectric conversion elements placed in the vicinity of the backlight 5 and the key light 3; control sections 6 to 8 for instructing the luminous quantity of the backlight 5 and the key light 3 on the basis of an electric signal outputted from the optical sensor 1; a light emitting element panel 10 for emitting a light to an original in response to a transmission instruction from the operation key 3; and a photoelectric conversion element panel 11 for receiving the light resulting from the light emitted from the light emitting element panel 10 and reflected in the original or transmitted through the original.