CMOS sensors generally have the disadvantage of generating electrical noise, which can result in poor image quality. There are unavoidable fluctuations in the performance of the millions of photodiodes and amplifiers incorporated into a CMOS sensor, and the tiny differences in performance result in noise in the output image. To overcome this problem, Canon developed on-chip technology to record the noise of each pixel before exposure, and automatically subtract such noise from the image when it is created. The addition of noise removal enables the reading of a noise-free signal. Some remaining quantum random noise is moreover removed by another technology known as complete electronic charge transfer.