Anyone in UK – PAL safe colours?

[Tobias Pfeiffer]

same for pal.
payton

[Jimmy Brunger]

Really? That’s weird, cos we sent out a test AVI to Adstream a little while back, who specialise in digital transmission delivery – they came back and said it was all legal and good for broadcast. I checked the levels in that same AVI and whites were 255, blacks were 0.

I’m not saying you’re lying or anything, it just doesn’t add up somewhere!?!
Do you know of any official site or any publications that state the 16-235 rule for PAL?

Thanks for your response.

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[Jimmy Brunger]

Yeah, Newtek VT[4] has a proc amp/vectorscope built in and we have the house legaliser (big rack mounted box in machine room) for output from the Editbox/Digisuite. Footage that has been through either of these and shown up as legal is still coming out 0-255 in the info palette in After Effects, or proc amp on VT[4]

I’m just a bit confused. We’ve never had anything sent back or questioned before, yet it seems 0-255 stuff is being seen as legal by our (some of it) expensive hardware.

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[Steve Roberts]

Googling led to this:
https://www.execulink.com/~impact/scopes.htm
PAL is mentioned in the thick paragraph halfway down.

There should be other articles out there, or you could ask at the Broadcast Video COW. I’m NTSC, so I’m not an authority. 🙂

[Jimmy Brunger]

Ahh…thanks Steve. Seems PAL is different: –

“PAL television transmissions in most countries can use 100% color saturation so no RGB color is illegal as long as your luma content doesn’t go over 100 IRE & your chroma content doesn’t go over 131 IRE. This is because most PAL countries use a wider channel bandwidth for broadcast than NTSC countries (7 or 8 MHz rather than 6 MHz) & because PAL transmitters don’t invert the signal before transmission.”

Learn something new every day! That’s tht bit of worrying done with.

Now, for this bl00dy font suitcase…..

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[Chris Zwar]

To add complexity to a very difficult topic, it really depends on your output hardware.

If you have a TIFF file with whites as 255 and blacks as 0, it will be output “legally” by a Cinewave card but “illegally” by a Media 100 card. While it’s common to find people mentioning the 16-235 range as being broadcast safe, it seems that many (most?) video cards these days treat 0 as black and 255 as white – which certainly makes life in AE much easier, although it may be bending the rules a little.

In the Meyer’s second book (I think it was the second) there is a table which lists different video hardware, and what outputs the 16-235 range and what uses the 0-255 range.

In fact the Meyer’s books probably discuss this issue in greater depth so if you don’t have them perhaps jump over to Amazon and buy yourself an early Christmas present 🙂

-Chris

Motion Graphics Designer
Will animate for food

[Jimmy Brunger]

Hi Chris,

Sorry – is this PAL you’re talking about or NTSC?

I’m just trying to acetane (thought I had it sussed!?!) whether 0-255 in PAL is legal to broadcast, not so much what the output hardware can handle, because at the end of the day it’s what a bog standard domestic TV can handle that mattters.

I’m further confused this morning (will this ever end?) by looking in AE once more at Broadcast Colors filter….there is an option for PAL there and when I bump up the saturation on an already 255 red the info palette never reads more than 255 (don’t think it can can it?) yet the ‘key out unsafe’ selection keys out some of the affected red. So, if it’s not more than 255 in the first place, why is AE trying to pull it back. Very confusing!

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[Chris Zwar]

Hi,

This really is a complicated issue so it’s not easy to sum up quickly.

Firstly, I re-read your first post and saw that you supply files to be software encoded via Cinemacraft. This is something I do a lot too. In the “advanced” tab of Cinemacraft you can specify whether your source file is 0-255 or 16-235. If you make sure this is set correctly you probably don’t have to worry about anything else. I think it defaults to 16-235, so I always make sure the guys encoding my stuff set it to 0-255.

However, to clarify my previous post, I was referring to both PAL and NTSC and the point I was making is that at some point along the line the animations you are producing are output as video, and the hardware which does that will determine how your levels are output. My point is that everyone quotes the figures of 16-235 as “broadcast safe” but that’s not always necessary, depedning on what video output device is being used. If you are using a NLE like Final Cut Pro or Premiere Pro to lay-off animations to tape then different video cards will output the same animation file differently. If you are supplying animation files to be software converted to MPEG2 (as you mention above) then your software needs to be told if you’re using 0-255 or 16-235.

So it isn’t as simple as just saying PAL and NTSC are both 16-235. Anyone who tells you that is grossly simplifying a horrifically complicated issue.

The final – and potentially more confusing – issue is that video treats the luminance seperately from the chrominance. Firstly, I’ll assume you’re using levels of 16-235. Your luminance levels may be legal (ie. 16-235) but the chrominance may be too high. An RGB value of 235,16,16 will be too red, even though it’s less than 235. Unless you’re some type of savant mathematician, you can’t precisely tell from an RGB value how “saturated” the colour is. You need a scope or some other plug-in to do this for you. In extreme cases- like the red example I just gave – it’s pretty obvious, but when you’re close to the limits (I think NTSC is more picky about yellows than PAL) you’ll need a scope to tell you, because you simply cannot look at an RGB value and know how that equates to saturation.

As I suggested before, try looking at articles (and books) written by Chris & Trish Meyer. They deal with it in great detail and hopefully will clarify the issue for you.

-Chris

PS. I haven’t checked, but AE comes with the Synthetic Aperture colour correction plug-in. The docs for this may cover the issue in the detail you require.

Motion Graphics Designer
Will animate for food

[Simon Roughan]

I also work in PAL broadcasting in germany, and the simplist way to be safe is anything you make in AE, put an adjustment layer on top with a levels effect set to 16-235 (black and white) and the gamma on 1.0. Like it was said above, the important thing is that your IRE doesnt go above 100. I check everything that goes out of my avid on a scope, and never have had a problem. And the people in the control room are quick to point out anything wrong, believe you me.