Reading the scopes in Video by Zaweba
The waveform, RGB parade, vectorscope with skin line and histogram in Video by Zaweba, and how to use them to judge exposure and colour by numbers.
Eyes are poor judges of colour. They adapt to a tint within seconds, and every screen shows a picture a little differently. Scopes give you a second opinion that doesn't change. In Video by Zaweba, View, then Scopes opens four of them: a waveform, an RGB parade, a vectorscope with a skin line, and a histogram. Each shows the picture as numbers drawn as a graph, so you can judge exposure and colour without guessing.
The waveform
The waveform shows brightness. Left to right it follows the frame from left to right, and up and down it shows how bright each part is. A face on the left of the shot appears as a cluster on the left of the scope, at a height that tells you how bright the face is.
Use it to check the ends of the range. If the bottom of the trace is pressed flat against the floor, the shadows are crushed and detail is gone. If the top is pressed against the ceiling, highlights have burnt out. A healthy shot usually uses most of the height without bunching hard at either edge, though night scenes and bright beach shots are allowed to lean one way.
The RGB parade
The parade shows three waveforms side by side, one each for red, green and blue. It is the clearest way to spot a colour cast. Find something in the frame that should be neutral, such as a white shirt or a grey pavement, and look at its trace in all three channels. If they sit at the same height, it is neutral. If blue sits higher, the shot is cool, and the temperature control or the blue curve can bring it back in line.
The vectorscope and its skin line
The vectorscope shows colour, not brightness. The centre is no colour at all. The further a point is from the centre, the more saturated it is, and the direction tells you its hue. A grey shot is a small dot in the middle. A shot full of strong colour spreads outwards.
The skin line is a guide drawn from the centre. Human skin of every tone tends to fall along roughly the same hue, so when a face is in frame, its colour should sit near that line. If it leans towards green or magenta, faces will look ill or sunburnt. It is one of the most useful checks in grading, because viewers notice bad skin long before they notice anything else.
The histogram
The histogram counts pixels at each brightness. Dark is on the left and bright on the right, and the height shows how many pixels sit at each level. It doesn't show where in the frame things are, which makes it less precise than the waveform, but it is quick to read. A pile against either edge means clipping. A narrow lump in the middle means a flat, low contrast shot.
Using scopes alongside the controls
The scopes are most useful open while you adjust. Move exposure and watch the waveform rise and fall. Move temperature and watch the parade's channels separate or come together. After a while you start to learn what each control does to the graph, and grading gets quicker.
The Colour page from the View menu shows a histogram and an RGB parade beside its large viewer. The full Scopes view adds the waveform and the vectorscope. It also helps when comparing shots: if two clips of the same scene have very different parades, they won't cut together well, however they look on their own.
Where scopes can mislead
Scopes report what is there. They don't know what you intended. A moody night scene should sit low on the waveform, and pulling it up to fill the range ruins it. Use the numbers to catch mistakes, not to force every shot into the same shape.
Read the right part of the frame, too. A small bright window can make the histogram look fine while the main subject is dark. The waveform, which keeps the left to right layout, is better at telling you about a particular area.
Scopes take a little practice. Once they make sense, Video by Zaweba gives you everything you need to grade with confidence on any screen.
