Join Maxim Jago for an in-depth discussion in this video The Waveform, part of Premiere Pro CS5.5: Color Correction.
When you're making adjustments to the luminance of your image, broadly speaking you've got three things that you're going to change. You've got the so called black level, that's the baseline of absolutely dark. You've got the gain, or the gamma, the midtones, that's the curve, if you like, of the range of luminance from dark to light. And then you've got the top of the range, you've got the whites, the highlights, the 100% luminance range. These 3 parts of your luminance are displayed inside the wave 4 monitor. And it's actually a very, very simple interface once you know what you're looking at.
First of all, you've got the vertical axis of this graph if you like which goes from minus 20 up to 120 but we're really interested in the bit of the scale that goes from 0 to 100. And if you working in the US or Japan and you're working with NTSC media, you're going to be using this IRE scale. And it's not really super important it goes from 0 to 100 and we can more or less refer to that as naught percent up to 100%.
If you're working in Pal, then you're going to be working in millivolts. And effectively, it's the same, but it's a scale that goes from 300 millivolts up to 1 whole volt. You're still looking at a similar graph, it doesn't make a huge amount of difference. Each of the pixels in your image, in this case we've got this shot of a model here, is represented on this graph. On the vertical axis, you're seeing the amount of luminance. There's no color information on this graph, this is just the brightness of each pixel.
The horizontal axis of this graph is the horizontal axis of your original image. So, you can imagine a column, if you'd like, of pixels taken from your original image and mapped onto this graph where the vertical position in the original image is no longer relevant. It's completely ignored in terms of the display on the wave form. Instead, the vertical axis represents how bright each pixel is in that column. And then you work your way along the image, column after column after column, left to right.
And you can see, quite easily, what's going on in this image. For example, we've got a range of dark pixels represented towards the right, and that's the whole area of dark pixels between our model's face and this column that she's leaning against. And then we've got some highlights on the column. And these are represented here, over on the right of the image. We have got some highlights on her hair on the left and there they all are. In fact we can see, we're burning out a little bit, we're cropping off our luminance, where the sun has caught the hair just in the top left hand corner of the image. There are some very simple controls on the wave form display. don't be confused by me having my sequence called the vector scope, that's just the sequence we happen to be looking at in this panel. It's the same as the panel menu that you get inside the program monitor, and in fact for that matter Inside the Source panel if you have a Source open. Let's open something up.
There we go. It's the same menu. We've got here the Intensity, which is just how bright the dots are, if you're finding on your screen it's not particularly clear or it's a little bit overwhelming you can change the Intensity. I'll leave mine on the default of 50. And we've got a Setup level, now. Setup is the word that refers to the baseline, the black level of your image, and if you're working with analogue source material than traditionally the Setup is 7.5 IRE, so we can effectively refer to this as 7.5%.
If I turn this off, you'll see that the whole of my wave form display shifts down a little bit, and the zero line now becomes my actual zero. Not this dotted line, just slightly above it, which is the 7.5 IRE zero point. I don't need to work with 7.5 IRE because I'm working with all digital source material. If I want to, I can view the Chroma overlaid on my wave form display. This is pretty useful for getting an overall sense of the composite image intensity, and that can be important if you're producing media for broadcast.
Because if you're producing media for broadcast, there are very specific rules about how intense the total signal can be. Of highlights and lowlights have to be, there's a range within which your signal must be supplied. And they'll just kick it back to you if you don't fit within those ranges. But I find generally I use the Vectorscope to display what's going on with my Chroma and a clean wave form display to see what's going on with my luminance. The wave form monitor is absolutely vital for seeing what's going on in your picture.
The eye is, or the human eye at least, is far more sensitive to luminance variation than it is to chrominance variation, so we need to make sure we've got nice strong shadows and highlights. That is of course if we want the picture to look good, and you may not want the picture to look good. You might want it to look dusky if you're doing day for night, you might want it to look moody or muggy. And the wave form display is where you're going to see if you're achieving that or not. Here I've got my shot of balloons, and you can see there's this band of luminance which is the sky, and then I've got the clouds, which represent much stronger highlights towards the right. And here, I've got a lovely gradient that goes from fully dark to fully light, and it's pretty much a smooth gradient.
And you can see very clearly what's going on in my wave form display. I've got the bottom end over here, of totally dark pixels leading up to totally light pixels on the right. Here I've got sky, and I've got a broad range of luminance, but you can see very clearly, I don't have very strong shadows in this image of the sky and the highlights aren't really making it up to 100%. And this means that if I wanted to perhaps add a greater sense of three dimensionality, a greater sense of, of reality tone to this image.
Rather then leaving it flat like that, you could make a nice background. But rather then leaving it flat, I might want to crank down the shadows and increase the highlights a little, it'll give it a greater tonal range. Here I've got a shot, a couple of kids on the beach. We can see the Individual on the left, the white t shirt here all displayed in the wave form. And we've got this banding here, we've got the grass over along the bottom and the sky along the top. Now you can see how tempting it is to image that the waveform display is somehow indicating vertical images. You can kind of see well, that kind of looks like a sky, that kind of looks like the grass, this is completely misleading.
It's just coincidental that the ground tends to be darker than the sky, and as I scrub through this you can see the movement. If I just zoom in a little on the timeline, you can see the movement of our characters as they run off down towards the beach. What you'll notice though if I press Play, (audio playing) is that the vector scope and the wave form, neither of them updated inside of Premiere Pro until you pause or unless you're scrubbing. Generally speaking, when you're making color corrections, you're going to begin with the contrast curve, you're going to get your shadows, midtones and highlights right before you move on to your color corrections.
And this means that the waveform monitor is your first go to spot in Premiere Pro for color correction. So that's an overview of using the wave form display in Premiere Pro.
- The color correction challenge
- Standard tools for measuring and adjusting color and light
- The Fast Color Corrector
- The Three-Way Color Corrector
- Other color correction effects
- Fixing and matching colors with presets
- Using After Effects for color correction