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Old 13th August 2015, 15:11   #7  |  Link
feisty2
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Join Date: Oct 2012
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always a pain in the ass when "color" stuff gets to be the problem
converting "matrix" alone is, not very correct more or less
"matrix" "transfer" and "primaries" are a set of interactive parameters work together as one to represent a certain part of colors from CIE 1931 (the very first color standard covering every single visible color to human vision, and device independent of course, kind like the royal of all color related stuff)
primaries = how red exactly is the red here (green, blue likewise), it decides the coordinates of 3 elementary colors (cannot be represented as some mixed stuff of other colors, they are the purest thing here, they get to mix each other to produce other colors) on CIE system
transfer = a function that connects physical intensity and perceived intensity (aka gamma)
matrix = a matrix to separate luminance and chrominance
so, see, HDTV got a different "matrix" not because "oops, the old bt.601 sucks ass, I don't like it, let's make some crazy new crap", "709" matrix is there because HDTV picks different primaries from SDTV, so a new matrix is needed to separate luminance and chrominance of the image based on this new primaries.
pointless to apply "709" matrix on clips with "601 NTSC/PAL" primaries cuz you can't get correct luminance and chrominance with this matrix, the "luminance" is not the exact luminance and so is the chrominance, the "matrix" does not serve as it's supposed to, and "601" matrix on "709" primaries, likewise
if you are that desperate to change the color system, don't just convert the matrix, convert to CIE 1931 and apply a whole new set of different color system.
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