
4.2.4 Grayscale Linearity
Another important display characteristic is the linearity of the grayscale. By this
we mean the degree to which the displayed brightness is proportional to input
gray level. Any display device has a transfer curve of input gray level to output
brightness. For proper operation, this curve should be reasonably linear and
constant from one use to the next.
Fortunately perhaps, the human eye is not a very accurate photometer [8].
Slight nonlinearities in the transfer curve, as well as 10–20% intensity shading
across the image, are hardly noticed. If the transfer curve has a definite shoulder
or toe at one end or the other, however, ...