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Color Legal
Hey guys,
How do you check to see if a HD spot’s color is Rec. 709 compliant? I was reading in the Black Magic UltraScope manual that a Vector Scope should not be used to check for legal color, but that you should use an RGB parade. I’ve also been trying to read about Rec. 709 to get a better understanding, but I can’t find anything that explains it in a simplified way, all I seem to find are technical documents that only a scientist could decipher. Could anyone help me?
Thanks,
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3 Replies
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The only reason we have “legal” colors is for analog equipment: analog equipment in the broadcast chain for SD, analog over-the-air broadcast (at least up until a few years ago in the US as we are now all-digital ATSC) and analog television sets.
Rec 709 as a color space represents a viewing space. Either a monitor can display a color or it can’t and kind of has nothing to do with a legal color pallet.
https://en.wikipedia.org/wiki/Broadcast-safe is what you should be reading.
In general you should be looking at the YC Waveform in Premiere or, ideally, in a hardware scope. Considering NTSC as my example Luma should be between 7.5 IRE (or 0 IRE outside of the US) and 100 IRE, and with chroma turned on it should be between -20 IRE and 120 IRE. A vectorscope can help spot saturation spikes which may cause chroma measurements to go out of range. IRE is a voltage measurement for analog signals.
If you’re mastering for DVD then black level is, so far as I understand it, always 0 IRE as the DVD player will bump it up to 7.5 depending on the set region or destined country of import.
Premiere also does full range YCrCb -> RGB conversion. You might have some people say that 0 IRE is mapped to the 16 gray and 100 IRE is mapped to 235 white. Premiere treats 0 IRE as 0 black and 100 IRE as 255 white for titles, graphics, and RGB-based video.
Premiere does do a lot of floating point math, that’s why you’ll see luma signal above and below 0-100 IRE but many export formats will truncate that information.
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Hey Angelo,
Thank you so much for clearing this up for me!!!
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The other thing to consider that is a pain in the butt is “setup” or “pedestal” which is the bump in black from 0 IRE to 7.5 IRE for the US.
DV tape, if I recall correctly uses 0 IRE all over the world. Other analog equipment like the tape deck might add setup, or a signal bump in the blacks, or it might not, as might other devices in the signal chain.
——————–
Angelo LorenzoNeed to encode ProRes on your Windows PC?
Introducing ProRes Helper, an awesome little app that makes it possible
Fallen Empire Digital Production Services – Los Angeles
RED transcoding, on-set DIT, and RED Epic rental services
Fallen Empire – The Blog
A blog dedicated to filmmaking, the RED workflow, and DIT tips and tricks
Can your post production question fit in a tweet? Follow me on Twitter
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