Latest post Mon, Jan 14 2019 2:10 PM by Pat Horridge. 4 replies.
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  • Sun, Jan 13 2019 8:53 PM

    • cunnin
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    colours/data levels wrong when exporting.. what to do?

    Hello fellow avid users - i have a problem with exporting, on several computers, pc and mac, several avid mc versions. When exporting from a 1080/25p sequence of sony pxw-x70 camera footage (also happens with canon 5d sometimes) the data levels gets messed up, and contrast er blown and black become crushed (see attached footage). I have through research come to the conclusion that it must be something about how the exported files are interpreted, because when i load the exported file back into avid, it becomes correct.

    Hope someone can help me, it would be greatly appreciated.

    Because this happens with the specific footage, no matter what computer or media composer version used, i have not supplied specs.

    thanks a lot!

  • Sun, Jan 13 2019 9:21 PM In reply to

    Re: colours/data levels wrong when exporting.. what to do?

    How are you exporting? What are your export settings, codec, format, etc?

    Also, this might be relevant: http://www.jobterburg.nl/Publications/601_709_RGB.pdf

    Media Composer /w Symphony option | PT-HD | Win7Pro64 HP | OSX MBP | ISIS5000 | Nitris DX | Artist Mix & Transport & Color | AJA T-Tap | Decklink... [view my complete system specs]
  • Sun, Jan 13 2019 9:44 PM In reply to

    • cunnin
    • Not Ranked
    • Joined on Mon, Jun 19 2006
    • Posts 8
    • Points 120

    Re: colours/data levels wrong when exporting.. what to do?

    I'll have those at hand tomorrow, but basically it doesn't matter how i export or what format, the error is as described in your pdf link (very valuable, thanks a lot!)
    So for the sake of ease, say that its a same as source, either “keep as legal” and “scale from…” makes 0-16 full black.
    The things you talk about sounds very much like the problem, however the settings options has been changed for a long time - I am currently on 2018.12.

    "Also note that the legal 16-235 lives inside a ‘regular’ digital picture, so if you look at a a picture that is 16-235 legal on a computer
    monitor (that is set up to display 0-255), the images may look dull, washed out, with too little contrast. But that is correct, as the image is
    not meant to be displayed on such a computer screen, but on a screen that has been calibrated to display 16-235 (like a properly set up
    client monitor).”

    and “Export with the ‘RGB’ option will make QT player remap luma levels (everything 16 and below will be displayed as full 0 black and
    everything 235 and over will be displayed as full 255 white).”

    What export settings should I use to export a file made for display on a computer screen? (0-255)

    Thanks again

  • Mon, Jan 14 2019 6:47 AM In reply to

    Re: colours/data levels wrong when exporting.. what to do?

    The settings you use do matter. Anything other than Same As Source may use certain QT codecs that may cause gamma shifts.

    As for the changed nomenclature, this is mentioned explicitly on page 1.

    Note that since MC version 8.4, these options were relabeled, and placed in a different order. “Computer RGB (0-255)” is now labeled “Scale from full range to legal range”

    “601 SD or 709 HD (16-235)” is now labeled “Do not modify, treat as legal range”

    The middle option to “dither image colors” has been removed.

    _IF_ you keep all levels legal inside Media Composer, and need a file that looks good on a computer screen, you would normally need to tick the expand option (previously labeled RGB), as that makes anything 0-16 appear full black on the computer screen and everything over 235 full white.

    Media Composer /w Symphony option | PT-HD | Win7Pro64 HP | OSX MBP | ISIS5000 | Nitris DX | Artist Mix & Transport & Color | AJA T-Tap | Decklink... [view my complete system specs]
  • Mon, Jan 14 2019 2:10 PM In reply to

    Re: colours/data levels wrong when exporting.. what to do?

    The export will only be correct if the ingest is correct and the levels handled correctly within MC. Use the colour corrector to lift the whites and drop the blacks and you will never create a correct output.

     

    So after ingest it important to look at the source settings and use the histogram to work out if any applied color adapter is correct or add one if ones needed.

    While grading use of external scopes or the inbuilt MC scopes is important to ensure video levels stay legal.

    Applying a legalising effect is often a wise move.

    Then making sure the levels are either left as TV legal or expanded to full range depending on whats needed for a SAS export. If you use the custom codec option all bets are off.

    ACI Moderator. I'm not employed by Avid or work for them. I just do this in my spare time. Normally using the current Media Composer version on My... [view my complete system specs]

     

    Broadcast & Post Production Consultant / Trainer  VET

     

    T 07581 201248 | E pat@vet.co.uk | W www.vet.co.uk |


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