A pixel circuit having a function of compensating for characteristic variation of an electro-optical element and threshold voltage variation of a transistor is formed from a reduced number of component elements. The activity being sensed can, for example, correspond to walking or running by a user. Preferably, one or more intermediate transportation electrodes are utilized, most preferably of monotonically decreasing size between the collection electrode and the array, so as to reduce current density mismatches. The composition can be applied to the human body to cause a reduction of fat in that area without an increase in fat in other areas. It is thus possible to prevent image failures resulting when the intermediate transferring member is started to be used from a new state or when the image forming apparatus is started to be used after a prolonged pause.