The value of R can be obtained by minimizing the mean
squared error between all subjective RRR values in the luminance
masking experiment (as shown in Fig. 3(a)) and the predicted
values according to the BJND model indicated by (6). The root
mean squared error (RMSE) scores under different values are
listed in Table I, which suggests the value for binocular noise
combination is within the range of [1.0, 1.5].