HDR Demystified
Luminance and Chromaticity - Because of the
perceptual interaction of luminance and chromaticity,
when a lower dynamic range display rolls off the top
end of higher luminance content, that also affects the
chromaticity of brighter pixels, and both need to be
taken into account in a displays color volume
mapping strategy.
For tone mapping and gamut mapping to be achieved
in the playback display, the display needs to be
informed by static metadata of the luminance and
chromaticity attributes of both the mastering display
and the content. These attributes are represented by
the static metadata fields that are defined in the
SMPTE ST2086 standard.
However, if color volume mapping is performed
without scene-by-scene content information, the
mapping will be based only on the brightest scene and
the widest gamut scene in the content. The majority
of the content will have greater compression of
dynamic range and color gamut than would be
necessary.
Dynamic metadata allows a compatible display to
map the content to a smaller color volume only as
needed, when the content exceeds the capability of the
playback display. The perception model can change
dynamically, based on the luminance and gamut
requirements of each scene.
Color volume mapping is more important the more
difference there is between the mastering display and
the playback display and will be an essential part of
the future proofing of HDR technology. It ensures
that playback displays that can do accurate mapping
will still show content well when mastering displays
are at or near the BT.2020 gamut limits, with many
thousands of nits.
-
http://files.spectracal.com/Documents/White Papers/HDR_Demystified.pdf
