A comparison device includes a multi-step pixel signal generation circuit coupled to a pixel to receive a pixel signal and generate a multi-step pixel signal based on the pixel signal according to a multi-step trigger signal and a multi-step size control signal; a comparison circuit coupled to the multi-step pixel signal generation circuit to compare a ramp signal with the multi-step pixel signal and output a comparison signal; and a control circuit coupled to the multi-step pixel signal generation circuit and the comparison circuit to detect crossings of the multi-step pixel signal and the ramp signal based on the comparison signal from the comparison circuit and output the multi-step size control signal to the multi-step pixel signal generation circuit.