Biased nature of Bhattacharyya coefficient in correlation of gray-scale objects

Bhattacharyya coefficient is a popular method that uses color histograms to correlate images. In this paper, we show that when this method is applied to gray scale images, it produces biased results. The biased nature is explored and demonstrated through numerous experiments with different kinds of non-rigid maneuvering objects in cluttered and less cluttered environments. The spectral performance of the Bhattacharyya curve is compared with the spatial matching criterion i.e. mean square difference.