Figure 6.

Empirically measured contrast sensitivity values. Comparison of the measured contrast sensitivity values (y-axis, left; dark blue circles) versus the nominal one from the Pelli-Robson (x-axis). The grey diagonal line shows the ideal reference, namely where the two sets of values are the same. The differences between the two sets of values (residual) are indicated as light blue stars (y-axis, right). The lowest logCS values can be obtained with a small deviation from the nominal ones, well below the 0.05 logCS level. The last levels show a bigger deviation and also a larger error, showing how these levels cannot be measured with the same accuracy obtained for the lower ones.