[opendtv] Re: New Chips Improve Color TV Dramatically
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 29 Jun 2004 18:17:04 -0400
John Golitsis wrote:
> And what Mark is saying is that you can't illustrate this
> with numbers.
>
> Really, you're all on the same 'wavelength', but talking past
> each other.
But Jeroen covered that, right?
The perceptual differences are not caused by the chromatic
space differences (if that's the right term) but by the
relative intensities? So I don't see why this doesn't
close the discussion.
Here's what Jeroen wrote:
> There is however a large and unfortunate difference between
> the coefficients of the Luma Function between ITU-Rec.601
> (SDTV) and ITU-Rec.709 (HDTV):
> Y' =3D 0.299 * R' + 0.587 * G' + 0.114 * B' versus
> Y' =3D 0.2126 * R' + 0.7152 * G' + 0.0722 * B'
>
> The first formula was derived from the luminosity of NTSC
> primaries, the second one was derived from that of Rec.709
> primaries. However, since the derivation is only valid in the
> linear-light domain but the formula is applied in the gamma
> domain, it is largely irrelevant which values are chosen.
> Poynton argues that it was senseless to change the values,
> it only leads to confusion and errors.
>
> So if you ever see wrong colours and you suspect that it is
> due to the difference between two standards: blame the Luma
> Function, not the colour primaries. Because the primaries
> are really not that different.
So what's left to be argued?
Bert
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