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How to Read a Digital WFM

WFM is an acronym for waveform monitor. Your waveform monitor shows you the luminance and chrominance of a shot so that you can quickly see any distortions in the video signals. Digital waveform monitors are used often in the production of television content to monitor video signal levels. Waveform monitors are helpful for determining the overall brightness of a shot and for adjusting and syncing video cameras so that they produce high-quality, visually pleasing shots. While a waveform monitor is a complex device, it’s easy to teach yourself how to read a few basic pieces of information about your shot.

Instructions

    • 1

      Connect your waveform monitor to the camera recording your signal and the monitor displaying your video output.

    • 2

      Examine the color bars showing on your waveform monitor screen. Observe the numbers ranging from zero to 100 on the left side of the screen dissecting the color bars. Each of the colored bars has a different luminance level, and they are ordered from highest luminance to lowest in this order: white, yellow, cyan, green, magenta, red, blue and black.

    • 3

      Press the “FLAT” button on your waveform monitor to view the entire video signal and see luminance and chrominance information at once. Press the “L PASS” button to view luminance information only and the “CHRM” button to isolate the chrominance information on your waveform monitor. If you’re having trouble viewing the information. press the “GAIN” button to magnify the screen image, making it easier for you to see.

    • 4

      Check the amount of gain in the video signal by checking the height of the color bars on the waveform monitor. If the bars reach above the “100” mark on the left of the screen, your signal is too bright. If the bars fall below the “0” mark on the left of the screen, your signal is underexposed and is too dark.

    • 5

      Press the “CHRM” button to check the chrominance of the signal to make sure the image is not over- or undersaturated. Look at the numbers on the left of the screen. If any of the bars extend below “-20” or above “+20,” you have an improperly saturated image.

    • 6

      Press the “MAG” button to display and analyze the sync pulse width of the chrominance signal. Verify that the vertical lines do not extend below “-20” and that the lines end on the “0” line.

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