“…This is just the case when a filtered image is perceived as having better visual quality. Dependences of optimal β for another HVS metric, PSNR-HVS-M (not presented in the paper), For more detailed analysis, we have further concentrated on two color images from the database TID2008 [41], namely the test image #3 (one of the simplest) and the test image #13 (the most complex one) (see Figure 1) since, according to our previous experience [17,18], just these marginal cases determine basic requirements. The test image #25 has not been chosen since it is artificial and we are more interested in enhancing natural scene images.…”