[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [OT] Video Standard Q: (Was Re: New Thread....about anything but Pulseaudio or yum)



On Wednesday 16 January 2008, Ed Greshko wrote:
>max wrote:
>> Does anyone want to discuss anything besides yum or pulseaudio? anything
>> at all? I wear a size 10.5 shoe. I don't like shoes without laces. I
>> don't like thick shoes.
>
>Well, I had one OT question rolling around in my head that I've resisted
>asking about.  It is having to do with displays and the sales literature put
>out by some manufactures.  I know there are folks on the list with broadcast
>standards experience...
>
>So, I wonder what "106% NTSC color capability" means.  If NTSC is a standard
>then how can you have over 100% capability?
>
>FWIW, I am looking to get a new LCD monitor and have run into that statement
>which makes me wonder.

I am a BC engineer, a practical one with 45 years of experience keeping a tv 
station on the air, but not a 'papered' one if you will.  I have set up 
enough systems that I don't ever trust my eyes without first checking the 
vectorscope to see if the signal is good in the first place.  If its not, I 
try to see if I can fix the signal's problems first.

I have seen some truly horrible color being displayed on both crt and 
lcd/ldp/plasma screens when the signal itself was good.  A goodly number of 
the light sources used in these displays are broken in terms of color 
faithfullness, so badly the display itself in front of that light source 
never has a chance to 'do it right'.

However, there are effectively two std's for color bars, and the one generally 
used is one where the peak white modulation caused by the subcarrier is held 
to 100 IRE on the waveform monitors display, a setting which is scaled from 
the rather arbitrary 0 to 100% power scale such that the 10% power point 
represents this peak modulation.  White, as generated by feeding an 
approximately 71% amplitude signal into all 3 ports of an RGB encoder, will 
come back out as a monochrome signal of this same roughly 71% amplitude, but 
to explain how that relates to the peak, if we feed a 71% red and a 71% green 
and a 0% blue, we will get an output whose luminance level is slightly 
reduced, containing the added color subcarrier in an amplitude that will make 
the waveform envelope on waveform monitors screen show a 100% peak white, and 
the vectorscope displays dot of this decoded color information should occupy 
the small box labeled y for yellow, which is a total lack of its complement, 
blue.

I could go on, but have probably lost the non-technical folks already.

I'll make another observation that will surprise a lot of folks here.  
Generally speaking, the vectorscopes display is race neutral.  The 
vectorscopes display of the human face/skin goes up the same degree line on 
the scope regardless of the racial content of the person being photographed.  
Far northern paleface, or blackest kenyan, its all the same to the 
vectorscope.

Even color blind people can adjust the controls on one of our processing 
amplifiers, using the vectorscope display, by waiting till there is a goodly 
amount of skin, as in a closeup of a face, and then putting that faces 
display blob as seen on the scope, on this line.  Everything else will just 
fall into place.  We have several people at the tv station who are color 
blind and do exactly that, and have been doing so for 20 some years.  Very 
talented people, and whom we've never considered their being color blind as a 
handicap.  In fact there are advantages to it, being able to see in the dark 
much better that I, with excellent color vision can, being one of those 
advantages.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Too clever is dumb.
		-- Ogden Nash


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]