Waveforms, Legal Range And The Differences Between Avid and Resolve

Waveforms, Legal Range And The Differences Between Avid and Resolve

May 18, 2013

Avid's Y Waveform sets black above the bottom of the scale whereas Resolve's Waveform sets its blacks at the bottom of its scale. Which is correct?


Series

Avid vs. Resolve: Waveforms & Legal Range Video

In Insights Article ML002 I did a comparison between the Curves controls in Avid Symphony and DaVinci Resolve. That video sparked a question about the difference between Symphony and Resolve’s Waveform Displays. Specifically, Avid’s Y Waveform seems to set black above the bottom of the scale whereas Resolve’s Waveform sets its blacks at very bottom of its scale.

The question: Which is correct? When you’re grading in Symphony, where should you set your black levels: To 16 bit as shown on Symphony or 0 bits as shown on Resolve?

Watch the Video below to find out the answer.

About Legal Range Video

In the process of recording this video, I imported a shot that had gone through After Effects and got tagged as Full Range Data, setting its black/white points to 0/255 bits within Avid… which is not appropriate for HD Digital video files but is clearly displayed on Avid’s scopes. I take a few minutes to explain what’s happening and how to properly fix this rather common problem using Avid’s Levels control… and how to handle in DaVinci Resolve whether you footage is rendered at Full Range or Legally Scaled Video levels.

If you’ve got questions or comments about anything in this video… please leave your comments below!

– pi

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Comments

10 thoughts on “Waveforms, Legal Range And The Differences Between Avid and Resolve”

  1. Thank you for the clear explanation! I agree that Resolve gets it right on Auto, most of the time. The case of H264, which you bring up at the end, is an exception in my experience. Rendering an H264 Quicktime out of Resolve defaults to REC709 scaled output. I find this odd because computer monitors display full range RGB, so most payback of the H264 will appear to have lifted blacks and compressed whites. This is most apparent when I have a client who wants to project from an H264 Quicktime or attach their computer output to an HDTV. In these cases, I have to manually select full range rather than auto when rendering out of Resolve. Things get really odd when rendering for upload to Vimeo. Vimeo appears to remap black to somewhere between 0 and 16, and white between 235 and 255. It’s quite odd. To get proper blacks, I find I’ve to export a file with black set to about 8 (in 8 bit) and white set to about 245. I’d be very curious to hear what your experience has been with getting proper levels when uploading to Vimeo.

    Another issue is how the auto setting interacts with Output LUTs for soft clipping. I’ve found that I have to use a different output LUT for soft clipping depending on whether I’m rendering out scaled or full range. Has this been your experience as well?

    1. Jamie,

      Because h.264 isn’t a traditional broadcast codec it don’t usually render out to that codec from DaVinci Resolve. I prefer to use Compressor or some other software suite that specializes in web and device delivery to handle that final step for those deliverables.

      RE: Vimeo – In our Mailbag #1 roundtable I think I mentioned at the end that I don’t like compensating for the vagaries of each of the video delivery services. My feeling: If I compensate for Vimeo’s encoding… then my images will look different than everything else on Vimeo – since everything else is suffering the same way.

      RE: Soft Clipping LUT – This is one feature I haven’t explored. I tend to do my clipping in nodes at the track level.

        1. Oh yeah, with Resolve using the GPU to handle all its rendering it’s blazingly fast compared to Compressor or AME. But for that one codec, h264, I’ll leave those renders for overnight… I just trust those other apps more for putting the blacks, whites and gammas in the right place when rendering to h264. But I haven’t done any testing on this – it’s just a habit (based on experience) I’ve developed over the years.

  2. Thanks for the info, Patrick!
    I’m still wondering though – what’s the best practice when grading in Resolve when planning to output to Rec.709?
    1 – Should we be concerned with grading within the 64-960 range? Or 2 – grade full range and then render out as legal?
    When using the second option, I saw that, after importing in Avid, the image looks quite different. The loss of contrast is really obvious.
    So I came up with a third technique – grade in 64-960 range and render out as “unscaled”. This way, I know that what I’m looking at in Resolve is going to match with the Avid. Do you thing it’s a good approach?
    * Forgot to mention – the renders are always MXF DNxHD.
    Cheers!

    1. When you say, ‘grade full range’… are you talking about ‘Full Range’ button in preferences? I’m a little unclear precisely about your workflow. Or are you visually setting black / white points to 64 / 960 when reading Resolve’s scopes?

      1. Yes, I was talking about vizually setting the image between 64-960 on the scope, then exporting the MXF as “Unscaled” in the Deliver page. This way I know I’m getting in Avid what I see in Resolve and I should be legal, right?
        Since you mentioned the video/data levels setting – this is just for monitoring and it should be set to what the monitor can handle, right?

        1. The Full Range / Legal Range button in preferences is for setting monitoring. If your decklink card is set to RGB monitoring then you’ll want to use Full Range.

          The Full Range / Legal Range button in the Delivery menu is for deciding where to set zero black and 100% white when writing the data out to the codec. For broadcast, rendering to a broadcast codec (such as DNxHD) I’ve gotten consistent results seting the Delivery settings to Auto.

          And in all instances grade with black at 0bits and white at 1023 bits. IME (even working with Avid), setting the Delivery option to ‘Auto’ will put blacks precisely where they need to be. If you’re still running into problems on import into Avid… it’s likely a mis-setting in Avid, seeing the footage as RGB and re-scaling to Legal. I’ve delivered to my Avid clients many times this way with good results (just be sure to also select the Avid Easy Setup).

          1. First of all, I have to mention that I’ve been doing this comparison judging on what the computer display shows.

            I’ve been doing some research on the forums and it seems a lot of people are in doubt about this. After all the reading, here’s the only thing that I could think of:

            Viewed on a computer monitor (that displays RGB), the Resolve GUI (that also shows RGB) shows a different image than the Avid Symphony GUI (which is now displaying a “legalized” image, with levels between 16-235); which would make perfect sense.

            And if I were to play the images on an external VIDEO monitor (with a proper SDI connection), the images would look the same. But that only presuming that Reolve is set to output video (not data) levels, right? Is this also the case for your grading suite? Is Avid showing something different than Resolve on the computer display?

            Thank you so much for your time and patience!

          2. Avid historically is built to be used with an external monitor – and that’s where you’ll get color accuracy. Because I never judge my images this way, I’m not willing to offer advice on how to make it look correct on the UI as opposed to an external display. And since I purposely throw off the accuracy of my computer display – I can’t say if Avid properly color manages the UI compared to the external display.

            What I’ve found in my Avid workflows, unless there’s a problem with the renders or with the import… the normal workflow is to grade between 0 to 1023 bits on the Resolve scopes, render out to legally scaled when rendering to a broadcast codec, and in Avid use 16bit as your black reference.

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