Re: Spectraview Software and Gamut Question
Re: Spectraview Software and Gamut Question
- Subject: Re: Spectraview Software and Gamut Question
- From: Graeme Gill <email@hidden>
- Date: Wed, 28 Nov 2007 17:00:20 +1100
J Richter wrote:
Sorry to post a seemingly naive question here... what is the
relationship in gamuts of NTSC vs Adobe RGB (among others) that gets
quoted by various monitor/display manufacturers? Samsung quotes 114%
wide gamut (of what? NTSC? Adobe RGB?) as well as stating Adobe RGB
support (yeah, to what degree, please!) for the XL20. NEC quotes a
number of 103% NTSC and equates that with 107% Adobe RGB for their
Spectraview. It would really be nice if every manufacturer would
indicate such standardized numbers for their product so that it will
give buyers a better / more level playing field when making technical
decisions, (among other specifications of course.)
It seems to be a fairly meaningless numbers game. For a start, NTSC 1953
colorspace has a green primary that nobody has used in a monitor for decades (ie.
all the "NTSC" TV's sold in the US don't conform to NTSC colorspace),
and the general way I understand such percentages are computed,
is to calculate the area enclosed by the colorspaces primaries
in CIE xy space, and compare them. Not only is xy space far from
perceptually uniform, the area comparison says little about how
well one gamut is enclosed by the other. So it really only gives
a rough measure of how big a colorspace is, not how useful it is.
If in fact you plot a colorspace gamut in 3 Dimensions in (say) CIELAB
space, it is evident that it is in fact very difficult for one
device to emulate another perfectly, unless the emulated colorspace
is relatively small, or the device has primary wavelengths that are
quite close to those of the colorspace being emulated. This is because
the primaries form "cusps", or "points", and the it's all to easy
for the "points" to lie in different directions.
These sorts of details are nicely concealed in a 2 Dimensional plot.
AdobeRGB is a strange colorspace. It is basically the European Broadcasting
Union (EBU) 1966 PAL colorspace, with the NTSC 1953 green substituted for
the PAL green. A story I've been told is that it started out as the EBU
profile in PhotoShop version 5.0.0, and a transcription error was made
in specifying the green, so in V 5.0.2, it was renamed "AdobeRGB".
[Someone with access to the V5.0.0 and V5.0.02 Photoshop releases could
possibly verify this story.]
Graeme Gill.
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