Ty Mr. Hullfish.
John,
How about popping those files up in the L2's files area with a link to
this thread?
DD
On 8/27/2012 4:33 PM, johnrobmoore wrote:
>
> Thanks for sharing with the L-2 group. If anyone would like to see the
> screen grabs and the actual files contact me off list and I'll send
> the same email to you that I did to Mr. Hullfish and others. I haven't
> had a chance to break out the calculator but it was obvious to me just
> using PhotoShop eye dropper that the I and Q RGB values were different
> in the various color bar files. Fun stuff for the nerd in me. Also I
> believe there is a debate over Union vs. NonUnion color bars in some
> circles. ;-) When I was in the unions I ended up in the bar every
> night. Now that I'm sober no bars at night and no union. Coincidence,
> Hmmmmmmmmmm. ;-(
>
> --- In Avid-L2@yahoogroups.com <mailto:Avid-L2%40yahoogroups.com>,
> Steve Hullfish <steve4lists@...> wrote:
> >
> > A week or so ago, John Moore posted some links to some color bar
> examples from the web and from Avid and asked:
> >
> >
> > I finally took a look at the Avid HD bars you mentioned and I do see
> the nice curly Q style of I and Q. I've included screen grabs off the
> Tek scope of 3 Bars The ARIB bars someone put up on the Avid L2, Smpte
> Bars of the 219 standard and Avid HD 1080 Bars. Interesting. I
> included the image files for each. So the challenge is which Steve H?
> Hullfish or Holmes will diagnose the image files and tell us how Avid
> got the math wrong for HD bars?. I'm betting it has something to do
> with the bigger stretch there is in HD bars as per one of the Tek
> seminairs. Here is what I've been told by Steven Holmes regarding 601
> vs 709 bars. Could this be the reason Avid bars are off? Have they
> just repurposed SD bars?:
> >
> > The response is only coming THROUGH me, but it is indeed from the
> other Steve... Holmes, from Tektronix, with the answer:
> >
> >
> > One thing we have to remember is that SMPTE Bars are a Composite
> color bar test pattern. I & Q do not exist in the Y Pb Pr or RGB domain.
> > You cannot go as far negative as you need to reproduce proper I & Q
> with full White. I & Q fall outside of the Color space we have to work
> with they are a reference Composite phase vector not a color.
> >
> > I had one of my colleges look at the files also, and here is his
> response.
> >
> > I had a quick look at the TIF files it appears as if they allow
> support of color range that BMP does not as white is set a 235 and
> black at 16.
> > Instead of white 255 and black at 0.
> >
> > Values of I and Q are from SDP2000
> >
> > G 40.68
> > B 166.75
> > R -144.56
> > Y -0.3 C 307.9 and 303 degrees
> >
> > G -97.61
> > B 258.27
> > R 94.41
> > Y -0.3 C 308.9 and 33 degrees
> >
> > So you cannot real produce I and Q values you have to change levels
> or degree in order to make it work.
> >
> > AVID values based on 16-235 for 0-700mv
> > For 219
> > G 62 = 146.4mv
> > B 102 = 273.6mv
> > R 4 = -38.2mv
> > Gives Y 107 C 307.9 and 303.2 degrees
> >
> >
> > G 4 = -38.2mv
> > B 115 = 273.6mv
> > R 64 = 152.7mv
> >
> > Gives Y 55.5 C 281.8 and 38.6 degrees
> >
> > For SMPTE Bars
> >
> > G 26 = 31.8mv
> > B 64 = 152.2mv
> > R 0 = -50.9mv
> > Gives Y 21.2 C 184.1 and 315.8 degrees
> >
> > G 0 = -50.9mv
> > B 80 = 203.6mv
> > R 58 = 133.6mv
> > Gives Y 33.9 C 248.0 and 46.4 degrees
> >
> > I choose for my pattern with RGB value 0-255
> >
> > G 0 = 0 mv
> > B 122 = 334.9mv
> > R 66 = 181.1mv
> > Gives Y 94 C 290.1 and 33.1 degrees
> >
> > G 64 = 175.68mv
> > B 107 = 293.7 mv
> > R 0 = 0 mv
> > Gives Y 134 C 291 and 302.8 degrees
> >
> > Therefore in AVID 235-16 would be about these value.
> > G 16
> > B 121
> > R 73
> >
> > G 71
> > B 108
> > R 16
> >
> > This concludes my math for the day.
> >
> >
> >
> >
> > Steve Hullfish
> > contributor: www.provideocoalition.com
> > author: "The Art and Technique of Digital Color Correction"
> >
> > [Non-text portions of this message have been removed]
> >
>
>
[Non-text portions of this message have been removed]
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