DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

Campbell, F.W., and V.G. Robson,
“Application of Fourier analysis to the
visibility of gratings,” in J. Physiol.
(London) 197: 551–566 (1968).
For video engineering, three features of this graph are
important:
• First, the 90 Td curve has fallen to a contrast sensitivity
of 100 at about 60 cycles per degree. Vision isn’t
capable of perceiving spatial frequencies greater than
this; a display need not reproduce detail higher than
this frequency. This limits the resolution (or bandwidth)
that must be provided.
• Second, the peak of the 90 Td curve has a contrast
sensitivity of about 1%; luminance differences less than
this can be discarded. This limits the number of bits per
pixel that must be provided.
• Third, the curve falls off at spatial frequencies below
about one cycle per degree. In a consumer display,
luminance can diminish (within limits) toward the edges
of the image without the viewer’s noticing.
In traditional video engineering, the spatial frequency
and contrast sensitivity aspects of this graph are used
independently. The JPEG and MPEG compression
systems exploit the interdependence of these two
aspects, as will be explained in JPEG and motion-JPEG
(M-JPEG) compression, on page 447.
202 DIGITAL VIDEO AND HDTV ALGORITHMS AND INTERFACES