The last method we will mention here is the method of
comparing histograms. This method involves comparing the
characteristics of light values of each pixel. Positive aspect
of this method is particularly the absence of the need to have
a reference image for comparison. Thus we can say that this
method is, in contrast to the comparison method, less
computationally demanding. Unfortunately, the main
weakness of this method is high error rate that occurs when
changing external factors and high number of noisy pixels.