Latest post Wed, Jan 29 2014 2:36 PM by jef. 233 replies.
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  • Fri, Jan 28 2011 9:19 PM In reply to

    • Radman
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    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    So The SDI from EX3 you are saying is not RGB but YCrCb the same as the NanoFlash.

    Both ( YUV )?

    So if this being correct there would be no remapping between the two units or from one to the other.

    Help file.

    If you are exporting from MC use ITU-R601 for (SD) or 709 for (HD).

    709 is this YUV?

     

    There should be a simple MATRIX for all this.

     

    Cheers

    Radman.

     

     

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  • Fri, Jan 28 2011 10:17 PM In reply to

    • cuervo
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    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    At the risk of getting too technical, here, YCbCr is the digital version of YPbPr. YCbCr is a digital way of describing an analog color space, namely RGB.

    Perhaps Wikipedia can describe it better than I...

    http://en.wikipedia.org/wiki/Ycrcb

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  • Fri, Jan 28 2011 10:21 PM In reply to

    • Radman
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    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    Thanks, I have read all the info.

    Just trying to get simple answer to the questions I pose.

    This might help others as well.

    Cheers

    Radman.

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  • Sat, Jan 29 2011 1:08 AM In reply to

    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    Radman:
    Sony EX3 I presume is RGB.

    I would not expect that. Most if not all video camera's are set up to record video levels (blacks at 16, whites at 235, with some headroom above that). If you want to know for sure, check the levels on a WFM.

    cuervo:
    ALL compressed recording formats are YCrCb

    RGB versus YCrCb is a different discussion.

    'RGB' in the import/export settings simply refers to 'full swing' (0-255) rather than 'studio swing' (16-235 / 601/709). Confusing nomenclature for sure.

     

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  • Sat, Jan 29 2011 6:06 AM In reply to

    • jwrl
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    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    Job ter Burg:
    Confusing nomenclature for sure.
    Damn right!  The confusion arises because RGB is used in two different contexts.

    RGB describing color channels says that Red, Green and Blue channels are directly used, whereas YCrCb refers to luminance (Y) and two color difference channels.

    RGB describing color space is, as Job says, defining full swing gamut as opposed to 601/709 which describes video legal ranges.

    So if someone refers to RGB get clarification!

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  • Sat, Jan 29 2011 12:37 PM In reply to

    • cuervo
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    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    yes, agreed. I think Avids reference to 'RGB' vs. 601/709 is a little ambiguous. Sony's Vegas, for example, refers to the difference as "studio RGB" vs. "computer RGB". Others refer to the difference as NTSC(Broadcast) vs. Full RGB. There is even a difference between Rec601 and Rec709, however, technically, both allow color ranges to be 0-255, even if Avid uses the term to describe 16-235.

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  • Sat, Jan 29 2011 3:18 PM In reply to

    • Radman
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    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    That's the perfect answer. I am sure many will be grateful for that.

    Sony EX3 is YPbPr/SDI out.

    A BIG thanks Job.

    Cheers

    Radman.

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  • Sat, Jan 29 2011 3:23 PM In reply to

    • BarkinMadd
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    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    I still find this thread rather confusing (I pretty much understand what I think Avid is doing). I decided to try the following test just to confirm and found that Avid is still doing something I didn't expect Stick out tongue.

    Here's the test you can try for yourself:

    Setup: Create an HDV image in Photoshop with 255 white on one half and 0 black on the other (1440x1080) - I've attached one to this posting (hopefully)

    Within MC I setup an HDV project with appropriate import settings. For this test, I'm going to try both RGB and 601/709 import settings).

    Next, import the PNG file using the RGB import settings and name this something you'll remember (such as TestImportRGB). Repeat this step but import as 601/709 and name it TestImport601.

    Create a new sequence and then cut both of these into your timeline so that you have 1 second of the RGB import followed by 1 second of the 601 import.

    Go into CC mode and use the color sampler eye-dropper to sample the white and black on both clips. On the RGB import you see white 235 and black 16. Avid's import converted the 0-255 of the import to legal 16-235 video (as explained in this thread). If you sample the 601 part of the clip, you'll see white 254 and black 1 (illegal video) - Avid didn't try to alter the clip because you told Avid to assume the import was legal. Again - this is as described in this thread.

    Next steps - select the entire sequence (2 seconds) and perform two quicktime reference exports, one using 601 settings and the other RGB. Call one ColorTest601 and the other ColorTestRGB to denote the two export options.

    You can then import each these back into your same project in MC, once using RGB and once using 601. You'll now have 4 additional clips in MC: ColorTest601as601, ColorTest601asRGB, ColorTestRGBas601, ColorTestRGBasRGB.

    The only surprise I had was the ColorTestRGBasRGB - Avid corrected the levels to video on import such that both portions of the clip were within legal range of 16-235 - I was expecting it to washout the portion that was already 16-235 as it did when I imported the ColorTest601asRGB. Upon reflection, Avid is doing the right thing.

    The only reason I'm posting this is to encourage any of you still unsure about this to try this test for yourselves - I still have to think about it a bit more but this certainly gives me some food for thought.

    Cheers

     


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  • Sat, Jan 29 2011 3:44 PM In reply to

    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    BarkinMadd:
    The only surprise I had was the ColorTestRGBasRGB - Avid corrected the levels to video on import such that both portions of the clip were within legal range of 16-235 - I was expecting it to washout the portion that was already 16-235 as it did when I imported the ColorTest601asRGB. Upon reflection, Avid is doing the right thing.

    Sort of. As levels cannot go below 0 and over 255, exporting something with illegal levels will not further illegalize them, but rather clip/crush them. So it makes sense, but you are not at all doing a clean, proper export import, and if it were an actual image, you would be losing detail in whites and blacks.

     

    If you really want to see what's happening, you might want to use Belle Nuit's Test Chart. It carries legal and illegal values (as it should). It should be easy to see what happens if you import and export with various settings. You will also notice as soon as you have crushed blacks or clipped whites, as you will notice that the difference between the 235 and 255 boxes and the 16 and 0 boxed will be gone.

    You should import as if it were 601/709, and all levels of this TIF are preserved. You can try and import as 'RGB', but then the levels in the image will be wrong after import.

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  • Sat, Jan 29 2011 4:10 PM In reply to

    • David Yardley
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    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    Job is doing a great job(!) but I just want to point out that Cuervo's point 2 above is incorrect:

    Using the RGB tab on export remaps levels.

    The general rule seems to be; always use 601/709 tabs unless you exporting for the web/computer viewing, or have a dumb DVD authoring package that does not understand broadcast levels.

    Please Avid relabel the tabs and provide clearer guidance in the manual.

     

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  • Sat, Jan 29 2011 4:24 PM In reply to

    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    NubusAvid:

    The general rule seems to be; always use 601/709 tabs unless you exporting for the web/computer viewing, or have a dumb DVD authoring package that does not understand broadcast levels.

    Is AvidDVD one of these "dumb" authoring packages?   I've been trying to get a definitive answer to that question, since that's the DVD authoring program I use.

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  • Sat, Jan 29 2011 4:35 PM In reply to

    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    cuervo:
    MC will export these values, up to 0-255 without remapping anything, as long as you choose RGB to export.

    Cuervo, the above is incorrect. When you export with the RGB option selected, there will absolutely be remapping.

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  • Sat, Jan 29 2011 4:41 PM In reply to

    • cuervo
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    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    Job ter Burg:

    cuervo:
    MC will export these values, up to 0-255 without remapping anything, as long as you choose RGB to export.

    Cuervo, the above is incorrect. When you export with the RGB option selected, there will absolutely be remapping.

    AHH! Thanx for the correction. I had ASSumed the remapping was happening in QT. But, upon further reflection, that's a dumb assumption.

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  • Sat, Jan 29 2011 7:21 PM In reply to

    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    Terry Snyder:
    AvidDVD

    The manual for Avid DVD seems to imply that you encode using Squeeze, then use Avid DVD to author and burn. In Squeeze, the advanced settings do carry a setting for sources that are already in the 16-235 color space.

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  • Sat, Jan 29 2011 7:25 PM In reply to

    • Radman
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    Re: RGB & 601/709 Color Space Settings - please check for accuracy

    My deductions with calibrated crt monitors.

     

    Two of the above mentioned test charts. Create ( TestChart_709 / TestChart_RGB ).

    Chart is a computer generated image RGB.

     

    Import TestChart_709 into MC as 709.

    Import TestChart_RGB into MC as RGB.

     

    Create timeline with both clips, 709 being the first.

     

    Export two quicktime files using animation codec at 100%

    First being exported as 709 then second being exported as RGB.

     

    TestChart_709 exported with 709 looks good. RGB not good.

    TestChart_RGB exported with RGB looks good. 709 not good.

     

    These outcomes would be correct for the Web or being viewed by a computer.

     

    BUT WE STARTED WITH A RGB IMAGE. Does this matter?

     

    Hope this adds up.

    Radman.

     

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