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Avid RGB export – black levels at 7.5 IRE?
Hi,
I work in 601 color-space and have found that DG Fast Channel only accepts my black levels if I export with RGB levels. They tell me my RGB-exported files read as 7.5 IRE but when I inspect the levels in After Effects, they read as 0 RBG, not 16 as would correspond with a 7.5 IRE.
I use Media Composer’s color safe limiter to set composite Low to 7.5 and High to 100…but I’m still having to export RGB and this seems counter-intuitive. I’ve exported 601 for other video distributors and had them NOT rejected as DG has…but maybe they just don’t care? Somebody’s wrong…and I’m not happy just going with “whatever gets accepted”…I want it to be CORRECT.
Which Avid export setting is correct for proper 7.5 IRE black levels, and should they indeed appear as 16 RGB when inspected in After Effects? Is there a better software available for getting an accurate reading?
Here are some pics, seems obvious to me the RGB export is web-black, NOT broadcast, but they’re telling me my encoded MPG is correct for broadcast…I don’t get it:
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6 Replies
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If you fly by your external scopes and export RGB, you will be fine. Blacks can indeed be crushed beyond 7.5 ire but are not illegal until lower than 0… getting into superblack at -10.
truth is, unless broadcasted on grandma’s old Curtis Mathis tube tv, it just doesn’t matter anymore. While that’s not a popular thing to say from a qquality control stand point, it’s spot on as LCDs, plasmas and projectors just don’t care.
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Hey Thanks Grinner.
Still, I am baffled at the discrepancy between the RGB levels I read in After Effects (16-17 RGB) and DG’s claim that I was somewhere around 15 IRE, likewise that my 0 RBG export was hitting their 7.5 IRE spec. Likewise again that another distributor had no problem with the 601 export that DG rejected.
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I suspect that DG systems hardware is adding 7.5 to the black level to bring it up from 0 (RGB black levels) to SMPTE levels. If you export a 601 file the black levels would already be at 7.5, add in another 7.5 on DG’s end and you arrive at 15. The other distributer you mentioned might be using a different decoder that doesn’t add 7.5 to the black level.
Regarding using AE as a reference point, there’s a lot that can go wrong with color management. There are color mngmt settings for the workspace, the individual files and the output – It would be relatively easy to interpret the data incorrectly. As Grinner has already said, external scopes are the best bet to ensure accuracy.
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One way to help point out to DG that they may have a problem (assuming they do) is to get a (reputable) 3rd party QC report indicating black levels etc, and send that on with your file. At least that way they might have a second look.
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3rd party QC and “reputable” only go together when comedy is the goal.
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Ha! True.
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