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 accurate image contrast
a display must closely match the Standard Intensity Scale.
Figure 3 below shows the measured Intensity Scale
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.
The iPhone 7 Intensity Scale is a very close match to the Standard.