Simplest way to judge if your levels are legal is to use the waveform monitor set to Studio RGB with the 7.5% IRE Setup unticked to measure Luminance not Composite. Anything below 0% and above 100% indicates that you luma levels are illegal.

You can still be "illegal" however the other errors are less of an issue and in general are unlikely to cause you too much grief and can be difficult to address.

For computer generated images and stills you can use any of a number of Vegas's FXs that have a ComputerRGB to StudioRGB preset. The Broadcast Colours FX has default presets that just clip illegal values which is probably not what you want to do.

Bob.

Sorry I wasn't clear... when I say 'Levels' for the vectorscope I mean 'Saturation Levels' not luminance levels.

Chris

1- Be careful: Vegas' scopes aren't necessarily accurate. You need to know what your codec is doing and (if applicable) what your digital -> analog converter is doing.

If you know that, then you can go into the settings and check/uncheck the 2 boxes in there.

When I add the NTSC color bars pattern and view it in the scopes, the colors hit the target values in the vectorscope... are these the legal limits?
No.

Vegas' color bars would be 75% color bars. There are 100% color bars, but some equipment (e.g. composite video) will have problems with them so they usually aren't used.

2- If your video may go down a composite video connection (e.g. anything SD, even digital formats like DVDs) then it's a good idea to make your video broadcast legal. One way to do this is to use the Broadcast Colors FX.

For countries that use 7.5 IRE setup, use the "Lenient - 7.5 Setup" preset.
For countries that don't use 7.5 IRE setup (all PAL countries and oddball NTSC countries), use the "Lenient" preset.

The lenient presets may not be conservative enough. You can drop the composite max setting down to 100-115 until the broadcaster stops complaining. (Doing this will affect your colors. If you want them to look good, you will need to use the secondary color corrector to darken highlights before the Broadcast Colors FX. Or, don't be overly conservative and create work for yourself when there is no need to.)

*May or may not be relevant: Things can happen to your video signal as it gets laid down to tape that can cause values to be illegal (e.g. sharpening)... you can't spot this in Vegas.

EDIT: see correction

[b](all PAL countries and oddball NTSC countries)[/B]

Hysterical!

Good technical substance-rich thread. Might I ask that more examples of where one uses a particular tool and why it could make a difference is the value here. This way it kinda sticks more with me - must be because I'm part of an oddball conglomerate of countries?

Grazie

Thanks Glen,

There may be the odd chance the video will go down a composite connection... just never know - Most Blu Ray players still have a Composite connection on them. After checking a commercial release for testing purposes encoded to a Cineform file (from an AVC source... thus 4:2:0 16-235), using the composite meter (scope) the values are well within 0-100 (scope being set to 16-235 so that 0 is 16). Looking at the vectorscope, saturation values are generally below 40% (this is a film based source BTW).

Which leads me to think that most studios are still using composite meters to view saturation and not a vectorscope. Try to google this info I get a lot of videos and articels saying that one should use the Vectorscope to keep and eye on the saturation - but if I push the saturation up on say my home videos (AVCHD decoded to studio RGB) up to about 75%, the the values in the composite scope go way over 100 and below 0 - yes I could use the broadcast color FX, which essentially clamps the luma, chorma and composite levels, which keeps it legals but often makes a mess of the colors.

So my conclusion - from what I understand - is that I need to lower the saturation and keep my eye on the composite level and not the vectorscope... but I wonder why so many articles and such say to use the vectorscope and to push the saturation levels up to 75%... most of the time when I do the they go beyond legal levels in the composite window.

Anyways... just curious....

Chris

"For countries that use 7.5 IRE setup, use the "Lenient - 7.5 Setup" preset."

My understanding is that 7.5% IRE setup should not be added to digital video. It is the responsibility of the D>A converters to add setup if required. Potentially adding setup into digital video will likely cause setup to be added twice.
All the NTSC compatible A/D gear I've come across has a 7.5% IRE switch.

Bob.

[edit] Found a reference that explains this better than me:

http://adamwilt.com/DV-FAQ-tech.html#Setup

My half cent.

There are two issues involved in luminance and chrominance levels as viewed in a Waveform monitor (any) and a Vectorscope (any).

As properly stated, the issue of 7.5 setup level is ONLy required in most NTSC countries that will transmit an ANALOG signal over the air or cable. In DIGITAL ATSC transmissions the 7.5 setup level is not required.

The Vectorscope measures relative chroma saturation and hue. The so called 75% block references are to calibrate the video chain BEFORE the Analog RF Modulator such that this latter will not overmodulate and cause distorion, again, in ANALOG RF transmissions. Also, this instrument measures the Color Subcarrier amplitude (and phase) going into said Analog RF Modulator. Digital ATSC transmissions do not use a Color Subcarrier, therefore, this level or reserve does not mean much to it.

A further point is that the reference Color Bars are artificial and represent the maximun expected chrominance that a video chain can accept. Thus, one sets up the related level, just like an ordinary audio control, to the maximum expected for best S/N and no more. Setup to 100% is perfectly ok for DIGITAL ATSC, provided that no other later signal will exceed this level, but not for any Analog RF Modulator which would overmodulate as stated above.. It is, however, ok to leave some headroom at digital levels both for blacks and whites.

This said, the observation that when a real life video signal is examined in a Vectorscope setup to 75% or 100% the signal looks much lower or weak, it is a correct determination because in real life there is practically nothing that resembles the color bars, except cartoons or computer generated images. But, to examine the real life signal in more detail, it is then perfectly permissible to increase the Vectorscope gain to view the relative amplitude and phase of the chrominance signal.

Another important point, already insinuated in the thread, is that the NLE Vectorscopes do not look at a real Chrominance signal but manufacture one from the individual RGB waveform components, which is ok since their relationship is fixed. BUT ......

In DIGITAL ATSC signals, the individual RGB component waveforms are perfectly ok to calibrate levels such that they stay within the A to D permissible range. However, to analize hue, only a Vectorscope or a Chrominance table can help, AFAIK.

For Grazie, CSI:Miami and its unnatural colors would appear in a vectorscope as flatenned along the I axis, which is Orange-Cyan ...

Cheers.

"A further point is that the reference Color Bars are artificial and represent the maximun expected chrominance that a video chain can accept. "

It is worth mentioning that the color bars in Vegas are built around REC 601 which is the older SD standard. Code for proper REC 709 color bars for HD is available, but not in Vegas. Unfortunately, they cannot be represented as an image file.

" Code for proper REC 709 color bars for HD is available, but not in Vegas. Unfortunately, they cannot be represented as an image file. "

I fail to see why they cannot be represented as an image file.
The problem is that Rec 601 and Rec 709 use different primaries, you can certainly create either as an image file, the problem would be that each image file would need to use a different colourspace.
Thankfully the difference is not huge however today there are cameras commonly available that use a wider gamut than either of those and this has become a major PIA for the industry. The problem does seem to have finally found a solution, put everything in a bigger bucket, the one provided by OpenEXR. If anyone is interested in the Academy Image Interchange Format there's an article on how "Justified" used this new pipeline here.

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Within the confines of Rec 601 Vegas does provide a tool that can give a clue as to what is really going on. In both NTSC and PAL land not all possible values of R,G,B are legal. If you open the Solid Colour Media Generator and swing the colours around you will see a little yellow triangle appear at some points. The triangle may display "!", "P" or "N" and these represent the following:

"I" = Out of gamut
"P" = Out of PAL gamut
"N" = Out of NTSC gamut.

Doing this while looking at the vectorscope can be sort of educational.
As far as I know using a convention video camera it is pretty well impossible to create out of gamut video. The same cannot be said for using any of the media generators unless you keep an eye on the warning indicators.

Bob.

My understanding is that 7.5% IRE setup should not be added to digital video. It is the responsibility of the D>A converters to add setup if required. Potentially adding setup into digital video will likely cause setup to be added twice.

What the Broadcast Colors FX does is that you get legalized colors when they are converted to analog. It doesn't "add" 7.5 IRE setup. But the whole concept of adding setup is confusing and silly anyways. It's easier to think of digital video as being converted to analog with or without 7.5 IRE setup.

Whether or not digital video is converted to analog with or without 7.5 IRE setup makes a difference as to what digital values are legal or not.

Stuff you don't really need to know:
To maintain hue and saturation (e.g. keep colors the same), the chroma signal needs to be proportional to the luma signal. If the legal range for luma is from 0 to 100 IRE, then you have 100 IRE to work with. If the legal range for luma is from 7.5 to 100 IRE, then you have 92.5 IRE to work with. So, chroma needs to be reduced slightly to keep the colors the same.
e.g. If you have NTSC equipment that wrongly converts digital to analog without 7.5 IRE setup (with 0 IRE setup), and you want to calibrate your monitor, you also adjust to change the chroma knob for correct colors.

And the whole 'chroma needs to be proportional to luma' thing affects the calculation of what is legal and what is not. So you need to know (or the FX filter needs to know) whether the digital->analog conversion will be with 0 IRE setup or 7.5 IRE setup.

As far as I know using a convention video camera it is pretty well impossible to create out of gamut video.
It's possible but rare.

A diffraction grating like the surface of a CD will create pure wavelengths. If they aren't contaminated by other light (e.g. glare off the CD and flare from your camera lens), then they will be a pure wavelength and no television can reproduce a pure wavelength (AFAIK anyways; no commercial TV will do it).

2- Cameras will also record values above legal white level, and weirdness can happen with the video knee.

"Stuff you don't really need to know"

Well knowing it certainly opened my eyes. Doing some tests with wedges, the FX and the 'scopes was educational, so thanks for telling me something I didn't need to know :)

Bob.

"I fail to see why they cannot be represented as an image file."

My recollection is that Y'CbCr luma coefficients cannot be adequately expressed in an RGB environment. I recall that Glenn has referred to this a couple of times in his articles.

"My understanding is that Y'CbCr luma coefficients cannot be adequately expressed in an RGB environment"

That's very easily solved though. Change what the RGB values represent i.e. get back to basics, "which red, green, blue". In other words change the RGB environment. Not that Vegas handles this at all of course and you'll like need to recalibrate your monitor or get a different one.

Bob.

If your video may go down a composite video connection
Actually I think I was confused here.

If your video may go down a RF / coaxial connection (can't remember the right name for it), then you have to worry about the same issues as broadcast safe. Also, some analog recorders can't handle very high composite values well (where composite refers to the luma and chroma signal combined, e.g. the composite view on Vegas' scopes). If you are making DVDs, you may or may not have to worry about this. It could happen if somebody's TV only has RF in (this does happen... some people buy RCA to RF converters for the old Nintendo systems because of this).

For HD, broadcasters will accept composite values over 120 IRE (i.e. if that digital signal were converted to analog, values over 120 IRE are ok). For SD they don't. If it's digital ATSC transmission, I believe you have to respect broadcast safe because some people out there will have digital ATSC -> analog converter boxes.

My recollection is that Y'CbCr luma coefficients cannot be adequately expressed in an RGB environment. I recall that Glenn has referred to this a couple of times in his articles.
It's not an issue.

Vegas will create the right Rec. 709 values (as long as you get studio versus computer RGB correct) as long as the codec is using the right formula. Nowadays it's unlikely you'll run into a situation where the codec is using the wrong formula (we would consider it a bug).

2- The TV might be using the wrong formula but as content creators you normally wouldn't worry about that. Early HD equipment like the first JVC camera uses the wrong formula.

3- There is the issues of different primaries but... I wouldn't worry about it. The de facto standard is to pretend the primaries are the same, and that is what Vegas does.

The article is here:
http://www.glennchan.info/articles/technical/hd-versus-sd-color-space/hd-versus-sd-color-space.htm

In regards to making things broadcast legal... composite max should be around 115. You can make your own Broadcast Colors FX preset for that. Or use 120 if you don't want to be that conservative.

The problem with the Broadcast Colors FX is that it changes colors in an ugly way. So if this is happening (and it may not happen depending on your source), use the secondary color corrector to lower the luma (called gain I think) on bright + saturated colors (you can target bright / high luminance + saturated with the secondary CC). Put the secondary CC before Broadcast Colors. You do this to make the colors look better while still being legal.

Glenn, the discussion Bob and I were having is whether REC 709 color bars can be correctly represented as an image file since they cannot be generated in Vegas; not how Vegas handles the conversions. I found the reference I was thinking of in your article on monitor calibration:

"You should not use images or video files downloaded from the Internet as there is a good chance that the levels will not be converted correctly due to Quicktime gamma issues, incorrect levels conversions, RGB color space limitations, etc. etc. Use color bars generated from the source that you are interested in (e.g. your NLE). Most current NLEs will generate proper color bars by default (except Sony Vegas 8; see my article explaining color space conversions in Sony Vegas)."

Also, doesn't 709 use black values that would be represented as negative RGB numbers?

Can you comment?

Which leads me to think that most studios are still using composite meters to view saturation and not a vectorscope.

Here's what's technically possible:
If you didn't have to worry about the guy whose TV only has RF in and you're making DVDs, then you wouldn't worry about how high composite max can go. So R=100% G=0% and B=0% will work. (Otherwise you need a lower value for Red, or use a less saturated red.)

Because in real world scenes it's unlikely you have to extremely bright AND saturated colors, the highest composite value never gets very high. So a lot of equipment is designed to not handle that situation so that more bandwidth can be allocated to everything else. Over the air broadcasting, VHS recorders, etc.

It's also possible to have the reverse problem (extremely dark AND saturated)... the most common way of this happening in Vegas is when the background defaults to 0 0 0 RGB and you don't stick a track of 16 16 16 RGB in (only if your encoder is expecting black to be 16 16 16 RGB).

Here's what broadcasters do:
If composite max is too high and they try to broadcast that, they will actually damage their equipment. So they do need to limit what colors are possible, R=100% G=0% B=0% will not fly.

Other than that, broadcasters are kind of weird because they all have different standards about what is legal and what is not. Their internal infrastructure may also be different and it may impose technical limitations that other broadcasters don't have. (e.g. they dub video to some silly analog format. I dont even know.)

Some of them will use one of the newer waveform/vectorscopes that log each and every time you have illegal values in the video. So if some engineer wanted to, it's possible to get incredibly, incredibly anal.

But anyways, for whatever reason, they all have different ideas about what's legal and what's not. In rare cases, they make an issue of things that don't matter. And also about how you should format your master tape (some of this is legitimate, because some countries don't run as many commercials so you need bumpers).

They definitely use waveform/vectorscope combinations, such as the ones by Tektronix. The newer ones will log errors.
They definitely use some sort of broadcast legalizer that will clip illegal colors. (Or if they don't....) This will probably make colors look like crap, so the content producer has to legalize everything so that the broadcast legalizer doesn't change the colors.

What content producers do:

In high-end facilities, they may own a broadcast legalizer and simply run everything through it. There is an art to making colors not look crappy, and a good legalizer / legalizing algorithm (e.g. not Vegas') will do a better job (like the secondary color corrector method). A good online editor will monitor the image after it has passed through the legalizer and may tweak even further.

In a telecine environment, I believe something similar happens though I'm not 100% sure. The gear definitely costs more money than online editing.

In the middle-end, you have schmucks who run Final Cut Pro. The legalization in FCP stinks because FCP isn't real-time most of the time and most FCP editors don't have that much experience in delivering for broadcast. So they will bounce back and forth with the broadcaster until the FCP editor figures something out, which might be a sorta dopey solution such as changing the proc amp settings on the ingest deck to deal with superwhites.
I suspect a lot of the time they work without looking at a set of hardware vectorscopes (which cost several thousand dollars). And they don't have a hardware legalizer.

Regarding whether or not color bars can be represented as in image...

The practical answer is like I said before:
Don't use images downloaded off the Internet. Use the generator in your NLE instead. But in Vegas, be careful about studio RGB versus computer RGB.

Now for non-practical theory:
Also, doesn't 709 use black values that would be represented as negative RGB numbers?
If you are using studio RGB (legal range from 16-235), then values below 16 RGB represent values blacker than black. So, it's possible to do color bars. (Ignoring rounding error.)

2- I don't believe that the Rec. 601 or 709 standards mention color bars in the standards article. I don't think think that there really is such thing as Rec. 601 / 709 color bars.

There are color bars that are commonly used for SD, and a different set that is commonly used for HD.

This thread has enough information to chew on for a long time. Kind of stuff I like to dig into even if I don't get it right away.

Thanks Glenn et al.