Vectorscope and YC Waveform 5.12.2014
Color correction for TV broadcasting.
When it is necessary to do export for TV broadcasting it is very important keep all picture data „in safe“. Here is a practical example how to do this quickly:
This is a source image as export from After Effects and is needed to correct it for broadcast.
At first time we open the Waveform monitor and will control the Highlights and Shadows.
Digital broadcasting allow use the highlights and shadow between 0,3 – 1,0. It depends on the software what you are using but always you get the same result. Some of them use percentage or different range of number. The waveform monitor represents only highlights on the top and shadows on the bottom. We see nothing there about colors. In our case we can see that image has many blacks / almost midtones and a few highlights. From this monitor we can exactly see where on the image is it, from the left to right only. So, for example. On top in the left is two brighter lines:
This lines represent white color in the ELMO MAKES MUSIC logo at the same position (top left). We can also see that shadows is ok becouse all lines is above 0,3 but few higlights is over 1,0. So we need to fix it. Generally for that is the best tool LEVELS where set the black and white input and outputs to 16-235 in every time. But in our picture we can use only highlight correction.
Now is the time make correction in colors. And therefore that waveform not representing colors we have to use Vectorscope. The Vectorscope shows us directly which colors and how many we are using, but there is no information where on image is it. The circle is the same as RGB circle. So you can see little letters what tell us what colors is there. R(red), MG(magenta), B(blue) etc… There are also few strange squares. 🙂 In my settings of vectorscope (75%) is important only outside squares. These represents the colors what is not good for broadcasting.
The bigger square is 20% tolerance and is possible to use it for broadcasting. But little one (maked from 4 little squares), is color what is not possible delivery to broadcasting. In mostly cases always red color makes trouble… 🙂 But of course is it not a rule.
In our spot we can see that red color is really over the limit so we need to fix it. Is many ways to do that. U can rotate the HUE, or change lightness of the color or just desaturate it for a bit. Usually, the best for it use some simple color grading tool like FAST COLOR CORRECTION etc. In my case I used in Adobe Premiere CHANGE COLOR, becouse i want separatelly move only red color. From my picture i can see that is only two red objects there. Elmo in left bottom & Elmo in the middle. I can see that left Elmo is brighter then Elmo in the middle. So i know, that middle one is the reason of our overlimit:
In this example i found on the end of video another problem with yellow color also (chicken) and I fixed it with same tool like red color. The result after all correction seems like this and is ready to delivery to the TV:
Vectorscope is also great for color grading of the people skin, when u need to be precise. The diagonal right from the red color represent skin color. It doesnt matter if is black, asian or white people. Every man is everytime on this line. There is different only position on it. So black people is closest to the center of the circle and white people is more far from it: