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RGB to YUV
I don’t know all that much about RGB and YUV colour spaces, but from what I understand so far, I believe RGB is considered 0-255 and YUV is 16-235 (with less information in the extreme blacks and whites, respectively).
Unfortunately, at the moment I have a predominately white looking film (think THX 1138) which I assume has been colour graded for RGB, because it looks great on my preview monitor but after an export (MainConcept AVC), all the whites are blown out leaving no detail in the video.
Is my only option to go back and limit the colour, effectively re-grading it? Or is there a format I can use that will retain the 0-255 colour values? I’m looking a distribution online and DVD.
EDIT: OK, so I’ve just found out that it’s ONLY Sony Vegas that has this issue with colours changeing during export. I tried a render from Vegas and a render from Adobe Media Encoder from the same source file and while the export from AME looks perfect, Sony Vegas has blown out all my whites. Anyone have any idea why Vegas is doing this?
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3 Replies
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[Lewis Costin] “Is my only option to go back and limit the colour, effectively re-grading it? Or is there a format I can use that will retain the 0-255 colour values? I’m looking a distribution online and DVD.”
You’ll need to grade it twice; once for on-line which is 0-255 and once for DVD which is 16-235. To make your video safe for DVD you’ll need to use Sony Levels with the Computer RGB to Studio RGB preset to bring the 0-255 into 16-235 range. Then watch your Waveform Monitor and use Sony Color Curves to bring back the contrast of your original image (but within the 16-235 range).
[Lewis Costin] “I tried a render from Vegas and a render from Adobe Media Encoder from the same source file and while the export from AME looks perfect, Sony Vegas has blown out all my whites. Anyone have any idea why Vegas is doing this?”
Because the Vegas Pro MPEG-2 encoder is smart enough to not send illegal values to rendered file. The file that Adobe produced is not broadcast safe and can cause problems if used. If you were submitting it for broadcast, it would get rejected by the station for having illegal values. Vegas won’t let you do this but it clips which is why you lost detail. Using the Levels filter will recalibrate the values rather than clip them.
~jr
http://www.johnrofrano.com
http://www.vasst.com -
Thanks John. I find the subject of broadcast colour quite confusing. Out of curiousity, does broadcast safe only apply to broadcasting? Will simply viewing on a DVD or online (Youtube/Vimeo, etc) have any relevance on colours if there are illegal values in the picture (i.e. 0-255)?
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[Lewis Costin] “Out of curiousity, does broadcast safe only apply to broadcasting? “
It apples to broadcast equipment in general (e.g., your TV set!) Not so much today with LCD’s but I can remember seeing commercials on an old CRT that had a buzzing sound whenever the titles were displayed. That was because their titles were pure white and the video signal bled into the audio signal. Some really old sets would loose vertical sync as well. So broadcast safe has to do with anything you want to watch on a TV set / DVD player.
Broadcast Safe has no application for Internet video which should be graded using the full 0-255. You should be aware that some sites like YouTube boldly assume that your video is Studio RGB (16-235) and expand it to Computer RGB (0-255) automatically making it darker than it should be if it’s already 0-255. So only grade for 0-255 if you will be hosting the video yourself or you know the hosting service won’t expand it.
~jr
http://www.johnrofrano.com
http://www.vasst.com
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