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NTSC Legal Colors (Weird Image)

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Kevin Reinicke
NTSC Legal Colors (Weird Image)
on Jan 25, 2009 at 9:07:08 pm

Please guys I need your help,

this is my first project (720p, 23,976) that gets broadcasted on satelitte TV and so I have to deal with the NTSC Legal Colors and I need some help. As far as I know the NTSC legal colors are between 16-235. I am within this range, but my vector scope image looks WEIRD, there are HOLES in between !!! (see yourself)

my project´s video scope image used to look like this:
http://s8b.directupload.net/images/090125/omn94jtg.jpg

when I apply "levels" and "broadcast colors" to it, I can bring the colors down within the 16-235 range and it looks like this:
http://s7b.directupload.net/images/090125/oh35dwip.jpg

But the video becomes a bit pale. When I try to fix this with some contrast plugin, I see holes in the video scope image.
http://s8b.directupload.net/images/090125/7jp22a5w.jpg

is this a problem ???? according to my video scope image (as you can see on second and third pic) I am within the 16-235 legal color range, is this all that I have to do to avoid distortion?


thanxs in advance




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Devin Crane
Re: NTSC Legal Colors (Weird Image)
on Jan 28, 2009 at 5:35:49 am

I don't know what you are using for your scopes. looks like an editing program's internal scope. If so most of them take a sample of the video and are not truly accurate. FCP does this to me after applying a filter in the vector scope. You should be fine as long as you applied your filters. We have only had 1 tape sent back to us in the past 4 years and that was because the deck was out of alignment. If your are working with a Major network I would recommend a high grade vector scope from Tektronix or leader.



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Kevin Reinicke
Re: NTSC Legal Colors (Weird Image)
on Jan 30, 2009 at 3:03:20 pm

Devin,

thanxs for your answer. Yes these are the scopes from Sony Vegas.
Is it normal that you can find holes between the color range? (like on my pics?)



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Devin Crane
Re: NTSC Legal Colors (Weird Image)
on Jan 30, 2009 at 6:40:51 pm

To my understanding yes. Editing Software inorder to conserve resources don't sample every line of video. Who are you sending the video to? You should be fine, unless you are dealing with a larger network like Discover, HBO and so on.



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Kevin Reinicke
Re: NTSC Legal Colors (Weird Image)
on Jan 31, 2009 at 10:31:42 am

my worry is that I am kinda fooling the programm :P

when I apply the broadcast color plugin the picture becomes a lot more pale (because I had a lot of saturated colors). so I put a brightness/contrast plugin right before the broadcast plugin and this kinda gives me the same look than before legal colors but this time in a legal range.

now I would be totally fine, if this trick wouldnt cause lots of holes in the vector scope image.

is there a way to test if this wouldnt cause distortion before sending?



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Devin Crane
Re: NTSC Legal Colors (Weird Image)
on Jan 31, 2009 at 3:29:13 pm

First-Get a professional Waveform Monitor from Leader or Tektronics, I've heard people using Veescope Software via a PC to do their color measurements and works.

Second- I would be looking at the Vectorscope and not the Histogram that's what engineers go off of to measure color and has the correct targets that will tell you if your are exceeding legal levels or not.

Check the settings on your broadcast safe filter, I'm not sure how Vegas operates but there should be some control settings that will allow you change how far to limit your colors and luminance levels.




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Kevin Reinicke
Re: NTSC Legal Colors (Weird Image)
on Feb 4, 2009 at 6:45:08 pm

Veescope is for MAC only right?? Is there anything comperable for PC?



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Devin Crane
Re: NTSC Legal Colors (Weird Image)
on Feb 4, 2009 at 6:54:11 pm

There is, unfortunately I can't remember the name at this time.

Sorry.



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Robin Palmer
Re: NTSC Legal Colors (Weird Image)
on Feb 6, 2009 at 1:20:32 am

The name of PC wavedorm monitor and vectorscope is Vidscope-VX
http://www.vidscope-vx.com

The reason for the gaps is the RGB histograms are the missing values after you have done a contrast stretch. This is quantisation and would be hard to see on moving video useless the stretch is extreme.

The quantisation errors may be seen as horizontal striations on a waveform monitor. When a contrast stretch is extreme it can lead to illegal levels (gamut errors) unless clipping or correction is applied afterwards - but the gaps will remain.



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