Re: [Avid-L2] Re: [OT] Calculation of luma SD vs. HD

Thank you both Terry and John for your answers. Not sure I get them, though.

"We have gone from small screens to much larger screens and needed better
resolution in the color space that the eye is most sensitive to."

To me this translates to: Human vision most sensitive to green -> we get mos
t of the perceived sharpness from the green channel -> we want to emphasize
this channel

Then there's this quote from the presentation:

"The transition to High Definition Television has introduced changes in the
colourimetry equations used and the type of phosphors used by the receiver.

The overall goal was to make the High Definition image have more vivid
colors to complement the increased luma resolution.

This has resulted in different R'G'B' to Luma and colour difference
equations being used as the television standards have evolved."

To me this means: Green is better, it pops more. Not sure I can follow that
logic.

So which is it? If I had to choose, I'd go with option 1.


Bye, Christian

P.S. I'm sure my wife would appreciate a giant chart in the living room. I'm
sure I could get the kids to help me paint one. They're great with crayons.


On Thu, Sep 6, 2012 at 8:07 PM, johnrobmoore <bigfish@pacbell.net> wrote:

> **
>
>
> I forgot to add that this kind of thread ROCKs the nerd in me big time.
> And thanks Terry for sharing more of Mr. Holmes knowledge. I also suggest
> going to the Tektronix web site. They have all kind of documents on various
> topics. You can even order some posters and charts, for free IIRC, that
> have great information. I can't say enough good things about the folks at
> Tektronix. And just think if you put up a neat Color Bars reference chart
> from Tektronix in your living room there's no way your wife can say it
> doesn't match at least some color in the room. Even Mauve, and I speak from
> experience on this. ;-)
>
>
> --- In Avid-L2@yahoogroups.com, "johnrobmoore" <bigfish@...> wrote:
> >
> > Check in the files section of the L-2 for the Color.pptx
> > This is a Tektronix seminar that deals with this. I forget if it gets
> into the why but it discusses what is the standard.
> >
> > Here is a brief explanation from Steven Holmes at Tektronix:
> >
> > Color.pptxColor.pptx
> >
> > For the most part if you are in 601 space you are OK or if you are in
> 709 color space you are OK.
> >
> > It is when you convert between them and use the wrong math.
> >
> > Luma is created differently in HD (709) there is a Big Space between
> Green and Magenta. In 601 there is not the big space.
> >
> > In each color space I & Q should fall at the same places
> >
> > HD Color Bars made with 601 colors will look bad on HD monitors
> >
> > See attached ppt..
> >
> >
> >
> > Steve Holmes | Sr. Application Engineer | Mobile: 909.225.6889 |
> E-Mail: steven.r.holmes@... | www.tektronix.com
> >
> > --- In Avid-L2@yahoogroups.com, Christian Foerster <public@> wrote:
> > >
> > > Hi everyone,
> > >
> > >
> > > this is not an Avid-specific topic, but I wouldn't know where else to
> > > ask and expect a good (and technically correct) answer.
> > >
> > >
> > > The luma component Y is a sum of fractions of the RGB components.
> > >
> > > For SD (ITU-R Bt.601) it's Y = 0.3*R + 0.59*G + 0.11*B
> > > For HD (ITU-R Bt.709) it's Y = 0.21*R + 0.72*G + 0.07*B
> > >
> > > Why has that calculation changed? I know the former was derived from
> > > experiments, so have they done new ones and found we are even more
> > > sensitive to green than we thought we were?
> > >
> > > I have googled, but beside many complaints about the fact have not
> > > found a satisfying answer. So if any of you know, please free me from
> > > the torment of thinking about this.
> > >
> > >
> > > Thanks,
> > > Christian
> > >
> >
>
>
>



--
http://www.filmeschneider.de
http://www.avidscreencast.com


[Non-text portions of this message have been removed]



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