FCP 7: How to Read Scopes

[ This article was first published in the June, 2004, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe. ]

Knowing how to read video scopes is critical to a variety of tasks with Final Cut Pro. This technique is designed to give you a basic understanding of how to read them, because in a future technique, I’ll show you how to use scopes for color correction.

Why use scopes? Because, it’s the only way you can be sure of your video and color levels.

Waveform Monitor

The Waveform Monitor displays the black, gray, and white levels in your picture. Think of it as a measure of your exposure. Each white dot in the scope represents the luminance, or gray-value, of a pixel in your video image.

A well-exposed picture will have lots of white dots at all different levels. A poorly-exposed picture will tend to have all the dots clumped in just a part of the scope.

Further, the waveform monitor directly corresponds to the image it measures from left to right. That is, looking left to right on the scope corresponds to looking left to right in the image. This means you can look at a scope and tell immediately where the dark and bright images are and roughly where they are located in the image itself.

Here’s an example. This close-up of a stage actor clearly shows the black background, and the close-up of his face in the center. (Images courtesy of Paul Jordan.) The heavy line slanting upward at the bottom of the scope is the dark gray of the background, with the fountain of pixels in the middle representing all the shades of gray in his body.

Notice that it is easy to see where his body is on the scope, but you can’t use the scope to identify specific features. The waveform monitor only shows the specific gray-scale value of each pixel in the image, and provides its position only in terms of left-to-right. The waveform has no concept of a pixel being in the upper half, or lower half, of the frame.

Here’s another example. This 3-shot shows three colorful actors. Notice how evenly the exposure covers the scope. There are whites, blacks and lots of different shades of gray. Remember, the height of the pixels on the scope represents their gray-level, with white near the top, and black near the bottom.

In general, images look better when they have lots of different gray levels, than when they all clump together.

If you are shooting DV, your levels will vary from digital black (measured as 0%) through to digital white (measured as 109%). If you are shooting Beta, your levels will vary from black at 0% to white at 100%. The area above 100% is called “super-white.” If you are outputting to DV, this isn’t a problem. If you are outputting for broadcast, you’ll need to use the scope to measure your levels as you adjust them, because they can’t exceed 100%.

(For more information on working with white vs. super-white, read this article.)

Vectorscope

However, the waveform monitor does not tell us anything about the color in a picture. For that, we need to use the Vectorscope.

The Vectorscope shows colors in two dimensions: the shade of the color, represented by where the color falls around the circle and the amount of color, represented by how far the color is out from the center.

On the vectorscope, black, white, and all shades of gray are represented by a single dot in the center of the circle. A fully-saturated color would be out near the edge of the circle.

One of the real values in using the vectorscope is that it helps us keep our colors, “legal.” Just as there are whites that are too white to be “broadcast-legal,” so, also, there are colors which are too intense to be safe.

There are six boxes in the vectorscope, representing red (upper left), yellow, green, cyan (lower right), blue and magenta. A color can be considered “broadcast-safe” if it falls within a loosely-defined rectangle drawn by connecting the tops of each of the six color boxes in the vectorscope.

Here is our first example, again. Notice that the colors are saturated (radiating far out from the center of the circle) and skewed toward yellow-red.

Here’s our second example. Notice the colors are much less saturated, though still pointing toward yellow-red, because the principal color in the shot is skin-tone.

One other things. See the purple line, at about a 45 degree angle from the top? This represents flesh tone. The magical thing about this line is that, in general, regardless of whether the skin of your talent is black, white, red, yellow or brown, their skin tone will fall on or near this line. This is because everyone has the same red blood under their skin, which provides the dominant color to skin. Knowing this makes color-balancing a whole lot easier.

Now that you know the basics of reading the two most important video scopes, you can use this knowledge to take your projects to the next level in quality.

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