-
Bars and Tone (HD 1080i60)
I have a question regarding the Bars and Tone (HD 1080i60) generated by FCP. Are these bars set at 100% saturation or 75% saturation? I did a search on posts and read some of the replies and to be honest I’m more confused than ever.
If the bars are at 75% then great. I assume they would also stay that way after you downconvert your HDCAM to digibeta?
If the bars are at 100%, how can I make them 75%? The same downconvert question applies here too.
I’d really like a straightforward answer as to whether the bars generated by FCP are 100% or 75% saturation.
Thanks for your help!
-
4 Replies
-
1- Saturation can be an ambiguous word. If you follow an intuitive sense of saturation (like the HSL color picker), then both 75% and 100% bars are 100% “saturated”.
If you mean chroma (and this is unintuitive), the 75% bars are 75% “saturated” and the 100% bars are 100% “saturated”.Perhaps this is why you are confused? Saturation can refer to either of these two concepts (and it probably shouldn’t).
2- In the bars generated by Final Cut, the chroma is 75% of the maximum (as opposed to 100%). This is the kind of color bars you usually see. The 100% bars (chroma is 100% of maximum) is illegal to broadcast (since broadcast is more limited in bandwidth than studio/production use) and not as commonly found.
3- Bars going from HDCAM to dbeta usually give you the correct SD bars. In rare occasions, you can get the wrong levels in the conversion- bars will let you spot this.
a- In consumer equipment (or poorly implemented equipment), they do not downconvert correctly.
b- (Nothing to do with FCP.) In some cameras, you can change the colorimetry setting so that the camera uses a different set of luma coefficients. The bars generated by the camera will reflect this.
c- The Teranex converters can tweak the colors of an image to account for differences between EBU, SMPTE C, and Rec. 709 phosphors/primaries. I believe this affects the color bars too. You can insert correct bars on the SD master. -
Thanks for responding glenn. So if one of my delivery specs is “SMPTE Color Bars at 75% saturation”, the FCP bars are a perfect fit? I think that’s what you’re saying.
-
Yep!
-
Great! Thanks, that’s what I needed to know!
Reply to this Discussion! Login or Sign Up