The Intensity Scale (sometimes called the Gray Scale) not only controls the contrast within all displayed images but it also controls how the Red, Green and Blue primary colors mix to produce all of the on-screen colors. The steeper the Intensity Scale the greater the on-screen image contrast and the higher the saturation of all displayed color mixtures.

Intensity Scale Accuracy
So if the Intensity Scale doesn't follow the Standard that is used in all consumer content then the colors and intensities will be wrong everywhere in all images. In order to deliver accurate color and image contrast a display must closely match the Standard Intensity Scale. Figure 3 below shows the measured Intensity Scales for the 4 Screen Modes alongside the industry standard Gamma of 2.2, which is the straight black line.

Logarithmic Intensity Scale
Both the eye and the Intensity Scale Standard operate on a logarithmic scale, which is why the Intensity Scale must be plotted and evaluated on a log scale as we have done below. The linear scale plots that are published by many reviewers are completely meaningless because it is log ratios rather than linear differences that matter to the eye for seeing accurate Image Contrast.

Note that the Intensity Scales for the different Screen Modes are very similar and overlap on the graph.
They are all somewhat steeper than the Standard Intensity Scale.