Luma, Chroma and Broadcast Safe

I was told to stay within the following guidelines for luma and chroma for a project:

1. luminance in the black areas must not fall below 7.5 IRE units (lower than 0%)
2. white levels must not exceed 100 IRE units (100%)
3. NTSC peak chrominancy plus luminance gamut must not exceed 120 IRE
4. Derived GBR values must remain within 0-700 millivolts."

I just wanna apply broadcast safe. My broadcast safe filter defaults to the following settings:

MODE: Conservative (115)
Luminance Limiting: Enabled
Luminance Clamp Above: 105
Luminance Max Output: 100
Luminance Start (threshold): 95
Saturation Limiting: Enabled
Saturation Clamp Above: 133
Saturation Max Output: 115
Saturation Start (threshold): 105
Saturation-Reduce Chroma/Luma: 100

Do my default settings meet the requirements mentioned above? I really do not know what the difference is between CLAMP ABOVE, MAX OUTPUT and START, so I don't know if I am ok with these settings. Thanks for any advice you can give me.

>1. luminance in the black areas must not fall below 7.5 IRE units (lower than 0%)

To note, black level adjustment is done on output to the tape deck. 0% on the FCP luma meter will be mapped to 7.5 IRE.

>Do my default settings meet the requirements mentioned above?

Unless you select the "use custom settings below", the meters are not in use, apart from the reduce chroma/luma (which will tell the filter how to treat illegal levels).

It is best to apply the 3 way color corrector to each shot first, and get them all legal before throwing on the Broadcast Safe filter to clamp anything that you may miss out, as overlimiting will cause shots to look quite bad and you may end up losing a lot of detail.



www.strypesinpost.com

The Broadcast Safe filter sux. It clamps everything & creates unnatural looking images (I notice pixelated clouds & water especially). Like G mentioned, I would use the 3-Way CC & I would use the scopes to tweak Broadcast Safe and stay away from that plug-in.

When life gives you dilemmas...make dilemmanade.

Hey, Joey:

Yeah, I know it is not the best option, but I have Color Corrected an entire timeline, just about 1/8th of the clips on the timeline are either over on luma, chroma or both. In order to save time, I would simply like to apply the filter and be done with it. If that is the case, do my default settings on the broadcast safe filter conform to the requirements I mentioned? In other words, if I can't go over 120 IRE on chroma plus luma, does the filter, when applied, automatically bring the levels down to safe?

<<<2. white levels must not exceed 100 IRE units (100%) >>>

...or the analog transmitter will start doing some really messy things. Usually, the luminance is clamped at 99 to 101 at the transmitter up on the hill, so this spec is just to keep surprises from happening. You sent super bright picture elements up to the tower on the hill and they didn't make it back to your living room. They're lying there on the floor of the transmitter shack where the white clipper put them.

<<<3. NTSC peak chrominancy plus luminance gamut must not exceed 120 IRE >>>

Which nobody in the US will ever actually broadcast. Our company stopped the broadcast color peaks from increasing past 110, again up at the transmitter. As was pointed out once, there isn't an actual broadcast specification for this, but most transmitter engineers would rather disembowel themselves than let you get anywhere near 120 with any signal.

My impression of the Broadcast Safe Filter is that it tries to adjust the overall picture quality so no parts of it are "illegal." This accounts for the complaints of funny looking pictures after application. You should see funny whites and distorted yellows if all it did was clip off the excess.

I'll have to watch it next time I'm next to one of the machines.

Koz

Quote

In order to save time, I would simply like to apply the filter and be done with it.

So in the interest of time, you would introduce artifacts willingly your image? I just don't get that.

When life gives you dilemmas...make dilemmanade.

>Do my default settings meet the requirements mentioned above?

They do. But FCP's BS filter is exactly what its abbreviation suggests, and as has already been clearly stated, depending on how out os spec your sources are, its likely the BS filter will balls it up. You should take pride in your profession and the content you produce and "in order to save time" shouldn't be an excuse for not color correcting properly. Onlining/Finishing is part of editing for broadcast and if you can't do that then you shouldn't be hired. (Sorry, but I regularly have to talk to editors who can't online when their work is fails QC so I'm ever such a little bit touchy on the subject! Believe me, the "I can't be bothered" arguments, or their derivatives, really don't wash.)

>I really do not know what the difference is between CLAMP ABOVE, MAX OUTPUT and START

When applying this filter you are asking FCP to remap pixel properties so that they fall within a specified range, and these values tell FCP how you want that remapping handled:

eg Start Luminance 95, Max Luminance 100 and Clamp Luminance 105 tells FCP to remap all pixel luminance values between 95 and 105 such that they fall within the 95 to 100 range ... any input values above 105 will be simply be treated as 105 (hence the clamp) and remapped to 100.

>but I have Color Corrected an entire timeline, just about 1/8th of the clips on the timeline
>are either over on luma, chroma or both.

That sounds like the one reason when NOT to use the broadcast safe filter! That, as Joey mentioned, will almost always introduce artifacts into your pictures. It's like not doing your audio mixing properly and expecting the limiter to 'unclip' your mix properly.



www.strypesinpost.com