1. An image sensor, comprising: a plurality of pixel units, respective ones of which include a pixel and a reset transistor, wherein the respective pixel includes a photoelectric converting unit configured to perform photoelectric conversion on light of a certain color incident through a color filter and a transfer transistor configured to transfer charges obtained by the photoelectric conversion of the photoelectric converting unit, wherein the respective pixel is controllable for each color, the respective reset transistor is connected to an analog to digital (AD) converting unit configured to perform AD conversion, the respective reset transistor configured to reset the charges, according to control of the transfer transistor, the charges are read from the photoelectric converting unit through the transfer transistor and the reset transistor, and a voltage corresponding to the charges is supplied to the AD converting unit connected to the respective reset transistor, the AD converting unit is connected to a power line that connects a drain of the respective reset transistor with a power source, and the image sensor further comprises a conversion control unit configured to cause the power line to enter a floating state, to cause the charges to flow to the power line in the floating state through the respective reset transistor, converts the charges to the voltage, and to supply the voltage to the AD converting unit connected to the power line.