How to use standard color bars in Waveform scope?

Zoloto
Zoloto Posts: 27 Just Starting Out

Hi all,

I have x-rite passport color checker for video. I know how to use it with a vectorscope to set correct hue and saturation. And I guess, the standard color bars in the waveform related to color correction, too, but how? Do they represent a brightness of each standard color? Any help please?

Thanks.

Best Answer

  • Triem23
    Triem23 Posts: 20,190 Power User
    Answer ✓

    You've brought up two things, the X-rite checker and "standard color bars."

    By color bars, are you referring to this pattern?

    In this case, the SMPTE color bars are for equipment calibration. With analog cameras and monitors it was very necessary to calibrate monitors in the field (using a "blue gun" method) then calibrate cameras with a remote color correction unit (CCU) in multicam setups so cameras would match before being recorded to tape.

    With digital broadcast cameras the bars and CCU are still used to match cameras before recording.

    (Color matching cameras is tricky. You can have three identical cameras and their sensors can still record color differently based on number of operating hours on the sensor, current operating temp of the sensor, noise/degradation from cable runs, variations in color temp from shooting angle - picture a seminar in a room letting in sunlight but with overhead lights where cameras closer to window shoot more "sunlit" and cameras away from the window shoot more "artificially lit." As the camera remains on, it will heat and color response will change. As the sun moves across the sky, white balance will change. Even in controlled lighting conditions color balance between cameras will require re-adjustment. I've been known to recalibrate cameras five or six times over a three-hour event.)

    For broadcast facilities, color bars (and audio tone) were striped at the beginning of a tape for the broadcaster to recalibrate audio and color levels for the individual program. There are marks on the scopes for where the bars SHOULD be to aid adjustments. Get the bars inside the scope markers and color is accurate.

    For small-scale digital production (individual use) there is little use for bars. Your camera most likely doesn't generate bars, most likely has any color controls buried in menus, and it's likely you don't have a production monitor with proper color calibration. If you do, this article might provide useful information.

    The Waveform monitor displays the individual RGB channel values in IRE ranging from 0 to 110 IRE in North American broadcast (and other countries on the same video standard) values below 8 IRE and above 100 IRE are illegal for broadcast (8 IRE=16, 16, 16 RGB, 100 IRE=235, 235, 235 RGB). For the internet and other video intended for computer/phone use, the full 0-110 IRE/0-255 RGB range is legal.

    Assuming you aren't working for TV broadcast, basically your waveform monitor serves two main purposes: making certain you don't "clip" massive detail at the 0 or 255 end of the range, and as a visual aid for color tints.

    With the X-rite your main swatches will be the "skin" tone (which you want on the "skin line" of the vectorscope) and the black/gray/white swatches (which you'd use with the waveform to adjust brightness range.


Answers

  • Zoloto
    Zoloto Posts: 27 Just Starting Out

    I referred to the "Standard Color Bars" option in Waveform settings. But from your answer I understood it doesn't relate to the case when we use color swatches of X-rite colorchecker for a hue correction. BTW in Waveform, the vertical axis, is it IRE or percentages?

    Thanks.

  • Triem23
    Triem23 Posts: 20,190 Power User

    Good question. 😁 I should have double checked that while writing the above response!

    Hitfilm's scopes are in percentage, not IRE

    100 IRE=94%