Measuring Video Levels with the Final Cut Pro Video Scopes

The Final Cut Pro video scopes work similarly to the standard scopes that you’d find in any online or color correction suite. The scopes provide exact measurements of the luma and chroma levels of your clips, helping you to unambiguously spot all of the hue, saturation, and luma levels that differentiate one clip from another. This lets you make more informed decisions about adjusting Final Cut Pro color correction filters to more closely match one clip with another.

The following scopes are available:

Opening Video Scopes Tabs

You can open multiple Video Scopes tabs and display a different scope in each tab.

To open a Video Scopes tab in the Tool Bench window
  1. Choose Tools > Video Scopes (or press Option-9).

    Figure. Tool Bench window showing video scopes.
  2. Choose which video scopes you want to view from the Layout pop-up menu.

  3. Choose the video frame you want to analyze from the View pop-up menu.

    For more information, see Layout Options in Video Scopes Tabs.

To open and use the Waveform Monitor and Vectorscope during log and capture, see Using Built-in Video Scopes During Capture.

Layout Options in Video Scopes Tabs

You can choose which scopes and which video source appear in each Video Scopes tab by using the following controls:

  • Layout: Use this pop-up menu to choose one of eight different combinations of single or multiple scopes for display in the Video Scopes tab. If you choose a single scope from the list, it takes up the entire space of the Video Scopes tab, making it easier to see. If you choose one of the multiple-scope layouts, all displayed scopes appear at a reduced size so that they fit into the Video Scopes tab at the same time.
    Figure. Shortcut menu showing choices of combinations of single and multiple scopes for display.
  • View: Use the options in the View pop-up menu to select which frame is being analyzed in the Video Scopes tab. Choose Current Frame to analyze the current frame at the position of the playhead in the Canvas. Other options allow you to select various edit points that are adjacent to the playhead in the currently selected sequence. You can also choose the frame at the position of the playhead in the Viewer. Choosing None turns off the scopes altogether.

    One way to use this feature is to pair up separate windows with Video Scopes tabs and Frame Viewer tabs, with each pair of windows set to display different edit points in your sequence for purposes of comparison.

    Figure. View pop-up menu.

Learning to Read the Waveform Monitor

The Waveform Monitor shows you the relative levels of luma and chroma saturation in the clip currently being examined. These values are displayed from left to right, mirroring the relative distribution of these levels from the left to the right of the image in the frame. Spikes and dips in the displayed waveforms correspond to hot spots and dark areas in your picture.

Figure. Viewer window and the Waveform Monitor showing hot spots and dark areas in a picture.

With the Waveform Monitor set to display saturation, you can compare the relative saturation levels of two clips by comparing the thickness of their displayed waveforms. Modifying the saturation of one clip to match that of another is simple; just adjust the Saturation control of one of the color correction filters in one of the clips to compensate.

Figure. Viewer window showing an image with high saturation and the Waveform Monitor displaying the image's saturation.
Figure. Viewer window showing an image with low saturation and the Waveform Monitor showing the image's saturation.

Learning to Read the Vectorscope

The Vectorscope shows you the distribution of color in your image on a circular scale. The color in your video is represented by a series of connected points that fall somewhere within this scale. The angle around the scale represents the hue displayed, with targets indicating the primary colors of red, green, and blue and the secondary colors of yellow, cyan, and magenta. The distance from the center of the scale to the outer ring represents the saturation of the color being displayed. The center of the scale represents zero saturation, while the outer ring represents maximum saturation.

Figure. Viewer window and the Vectorscope showing a representation of the Viewer's image.

The Vectorscope is useful for seeing, at a glance, the hue and intensity of the various colors in your image. Once you learn to identify the colors in your clips on the graph in the Vectorscope, you will be better able to match two images as closely as possible because you can see where they vary. For example, the image above has points of intense red and areas of vivid blue, which you can spot immediately on the Vectorscope. The underwater image below contains predominantly blues, which present an entirely different profile on the Vectorscope. Although this is an extreme comparison, by looking at various images and studying how the Vectorscope changes you’ll learn how to spot the information you’re looking for.

Figure. Viewer window showing an image of dolphins and blue water and the Vectorscope showing a representation of the Viewer's image.

The color targets of the Vectorscope scale match the colors in the color balance controls of the Final Cut Pro color correction filters. If the hues of two shots you’re trying to match don’t match, the direction and distance of their offset on the Vectorscope scale give you an indication of which direction to move the color balance indicator to correct for this.

The Vectorscope is also helpful for identifying and correcting the flesh tones of actors in a shot. When recorded to videotape and measured on a vectorscope, the hues of human flesh tones, regardless of race, fall along a fairly narrow range (although the saturation and brightness will vary). This range is identified by a special target line that indicates the average hue of flesh tones. When there’s an actor in a shot, you’ll know whether or not the flesh tones are reproducing accurately by checking to see if there’s an area of color that falls loosely around the Flesh Tone line.

Figure. Viewer window showing a face and a vectorscope representation of flesh tones.
Figure. Viewer window showing a face and the Vectorscope showing a representation of face's flesh tones around the Flesh Tone line.

If the flesh tones of your actors are noticeably off, the offset between flesh colors on the Vectorscope and the Flesh Tone line will give you an idea of how much to change the hue to make the correction.

Learning to Read the Histogram

The Histogram shows you the relative distribution of all luma values in the video frame at a glance, from black to super-white (assuming the video codec you’re using supports Y′CBCR processing). It’s really a bar graph of sorts, where the x axis represents a percentage of luma, from 0 to 110 percent. The height of the line at each step on the scale represents the number of pixels in the image at that percentage of luma, relative to all the other values. For example, if you have an image with a lot of black pixels, you would expect to see a spike in the Histogram near the luma range of 10 to 20 percent.

Figure. Viewer window showing an image of a cat and the Histogram illustrating the distribution of luma values in the image.

The Histogram can be very useful for quickly comparing the luma of two clips so you can adjust their blacks, midtones, and whites to match more closely. For example, if you were matching an insert (or close-up) clip to the clip shown above, the overall luma levels might have shifted because of a change in lighting or exposure. You can easily see such differences in the Histogram and correct for them. For comparison, the image below has a lot of whites, so the Histogram shows a cluster of values at the high end of the scale, with a spike at 96 percent.

Figure. Viewer window showing an image of a polar bear on snow and the histogram illustrating the luma levels in the image.

The shape of the Histogram graph is also good for determining the amount of contrast in an image. A low-contrast image has few pixels in the extreme black and white ranges, so the Histogram shows a concentrated clump of values nearer to the center of the graph. By comparison, a high-contrast image has a wider distribution of values across the entire width of the Histogram and may have spikes at white and black.

Figure. Two Histograms graphs illustrating a low-contrast image and a high-contrast image.

Learning to Read the RGB Parade Scope

The RGB Parade scope is like three side-by-side waveform monitors that display your video as three separate red, green, and blue components. The waveforms are tinted red, green, and blue so you can easily identify them.

Figure. Viewer window showing an image of a couple dancing and the RGB Parade scope illustrating the red, green, and blue waveforms of the image.

The RGB Parade scope is useful for comparing the relative levels of red, green, and blue between two clips. If one clip has more blue than another, the difference shows up as an elevated blue waveform in the one, and a depressed blue waveform in the other. In the previous screen shot, the overall image contains quite a bit of blue. By comparison, the shot of the couple dancing below has substantially less blue and far higher levels of red, which can be seen immediately in the RGB Parade scope.

Figure. Viewer window showing an image of people dancing and the RGB Parade scope illustrating the red, green, and blue waveforms of the image.

Choosing Display Options for Video Scopes

Each video scope has several display options you can choose, such as brightness, color, and standard measurement areas (called targets).

To see video scope options that are currently displayed
  • Control-click anywhere in a video scope.

    Options that are turned on, or displayed, have a checkmark next to them.

    Figure. Shortcut menu in the Waveform Monitor showing that checkmarks appear next to options that are turned on.

Adjusting Scope and Scales Brightness

The following controls allow you to control brightness of the video scopes. Brightness control is helpful for revealing minuscule areas that otherwise might be invisible on the scopes.

  • Display brightness: Controls the brightness of the video lines (or traces) shown on each scope.
  • Scales brightness: Controls the brightness of the grid lines (known as graticule lines on traditional video scopes).
To change the display or scales brightness of a video scope
  1. In the Video Scopes tab, click the Display Brightness or Scales Brightness button above the video scope readout.

    Figure. Video Scopes tab showing the Display Brightness button and the Scales Brightness button.

    Depending on the button you click, the Display Brightness or Scales Brightness slider appears.

  2. Drag the slider to increase or decrease the brightness of the scope.

    Figure. Two Video Scopes tabs showing the Display brightness set to low and then set to high.

Additional Video Scope Display Options

You can access the following additional video scope display options by Control-clicking within a video scope.

  • Green, White, Pale, and Bright: The waveforms displayed within all the scopes can be green or white, depending on which color you find easier to look at. Final Cut Pro defaults to white, which is the preferred display color because it doesn’t bias the eye toward any particular color.

    Note: In the RGB Parade scope, the waveforms are tinted red, green, and blue, so these options become Pale and Bright.

  • Saturation: This option is available in the Waveform Monitor only. With saturation turned off, the waveforms display only the luma of the selected video signal and appear to be a series of lines or dots. This can be useful if you’re interested solely in the relative luma of different parts of the video frame. With saturation is turned on, these lines expand vertically to appear as a much thicker series of waveforms. The thickness of the waveform represents the amount of saturation in the chroma of your video clip.

    Note: The color bar targets displayed in the Waveform Monitor change automatically, depending on whether or not saturation is turned on.

  • Include Black: This option is available in the Histogram only. Turning on this option scales the Histogram’s height to include the blacks in the picture. Turning off this option scales the height, ignoring the blacks. You may want to turn on this option if there’s a lot of black in the clip you’re viewing, to help you get a clearer profile of all the whites and blacks in the clip. You may turn off this option if you’re performing compositing tasks, such as placing a small image against a black background, in which case it’s unnecessary to view the excess black information because you know it’s there.
  • Magnify: This option is available in the Vectorscope only. Turning on this option zooms in on the inner 55 percent of the Vectorscope’s display, letting you see more detail in images with low saturation.
  • Targets: This option displays the ideal targets you use to calibrate a video signal generated by color bars.

Using Video Scopes in Real Time

Depending on the format of your video and the processing capabilities of your computer, the Video Scopes tab can update in real time using the same level of quality available in previous versions of Final Cut Pro.

To turn on real-time updating in the Video Scopes tab
  1. Open a sequence in the Timeline.

  2. In the Timeline, choose Video Scopes Playback from the RT pop-up menu, so there is a checkmark next to it.

Note: Using the Video Scopes Playback option requires additional processing power. Turning on this option could result in a red render bar in the Timeline. Also, the Video Scopes tab may not update in real time with some formats. For example, playing back an HDV multiclip requires significant processing power, so the Video Scopes tab may not update in real time in this situation.

Choosing Video Scope Accuracy

You can choose three levels of analysis accuracy from the RT pop-up menu in the Timeline:

  • All Lines: Every pixel of every video line is analyzed, and pixel values are displayed in the Video Scopes tab. The word “all” appears in the lower-right corner of the Video Scopes tab.
  • All Lines Except Top & Bottom: Displays every line except the top nine and bottom nine lines, which are reserved for signals such as closed captioning. The word “most” appears in the lower-right corner of the Video Scopes tab.
  • Limited Lines (Fastest): This mode is always used during real-time playback. Accuracy is limited to 32 lines that are evenly distributed from the top to the bottom of the action safe area of standard definition video. This is sufficient to catch video elements whose height equals 5 to 10 percent of the total size of your image.

Important: The accuracy level you choose here affects video scopes when the playhead is paused or scrubbing; real-time video scope updating always uses the Limited Lines (Fastest) option.

The lower-right corner of the Video Scopes tab indicates the scope display option selected in the RT pop-up menu.

Video Scope Restrictions and Performance

The following list describes limitations when using the Video Scopes Playback option in Final Cut Pro:

  • You must be using a format that Final Cut Pro can process in real time. For a list of formats that Final Cut Pro can process in real time, choose Final Cut Pro > System Settings, then click Effect Handling.

  • The View pop-up menu in the Video Scopes tab must be set to Current Frame (referring to the Canvas) or Viewer. Options such as Current Frame w/o Filters and Previous Edit turn off the Video Scopes Playback option.

When checking video scope accuracy, you can analyze all video lines only when playback is stopped or when scrubbing. The Video Scopes Playback option updates the Video Scopes tab using the Limited Lines (Fastest) option. For more information, see Using Video Scopes in Real Time.