DaVinci Resolve – How to Use External Scopes with Video vs Data Levels

March 2, 2016

Learn how the 'data levels' and 'video levels' Project Setting effects your external scopes when color correcting in DaVinci Resolve.


Series

A follow-up to understanding Video Levels and Data Levels in DaVinci Resolve

Do you remember when to use the word ‘affect’ vs the word ‘effect’?

From the Grammarist website comes this definition of effect vs affect:

Affect is usually a verb, and effect is usually a noun. To affect something is to change or influence it, and an effect is something that happens due to a cause. When you affect something, it produces an effect . . .

But the words have other, less commonly used senses that can make them tricky.

Effect does function as a verb when it bears the sense to bring about. For instance, it is the correct word in phrases such as effect change and effect solutions where these phrases mean to bring about change and to bring about solutions.

It’s possible to imagine where the phrase affect change might make sense, but it would mean to have an effect on change rather than to bring about change.

Sigh.

You can read that three times, think you understand—only to realize 45 minutes later that you’ve forgotten how it’s possible to have an ‘affect on an effect’ and which begets which.

Video Levels vs Data Levels is just as confusing as Effect vs Affect

You can read the previous Insight I dedicated to this subject (where you learn how to decide when it’s appropriate to choose Data Levels over Video Levels but why in most cases you just want to leave those settings to default) and still walk away confused about which settings to choose. Especially when figuring out how you should analyze your image with scopes, depending on those settings. And that’s what you’ll be learning in this Insight.

How Does Your Choice of Video Levels vs Data Levels Effect Your Reading of External Scopes?

This is super-confusing when you first try to wrap your brain around this concept. Especially in DaVinci Resolve, which gives colorists and editors explicit control of these settings—because very few other post-production software makes the ‘video level vs. data level’ choice so obvious and easy to affect (or is it effect???). It’s easy to work in this business for a decade and never have to think about Video Level data encoding.

Now, it didn’t take me long to figure out that my previous Insight on this subject glossed over an important aspect of this discussion. From the comments of Mixing Light members on that Insight:

“The importing thing for me is that 940 is the top legal code value on an external scope.”

Steve MacMillian

“This topic would need to have some animations to explain it better maybe?”

Margus Voll

“OK! I follow Patrick’s “orders”; I touch nothing. I acknowledge everything that he says and I go away happy.

BUT! Then I look at my scopes and they range from 1-1023.

And I have a neat setting that allows me to “Show Reference Levels”. So I set that to [64] and [940] and neat lines are added to whatever scope I set that display on in.

So do I grade my blacks to sit at [0] or do I grade them to sit at [64]? And if I grade them to sit at [0], I assume Resolve will do all the necessary range adjustments as required.
And then, of what value is being able to see lines on a scope at [64] and at [940]?

Anthony

 I hear you, Steve, Margus and Anthony!

You’re still confused. But I also know where your confusion comes from (since I was once just as confused about this specific aspect of this subject).

I can’t leave you where I did in that previous Insight (which focused on how Data and Video Levels get saved out upon rendering)!

I glossed over the fact that there’s a whole separate pipeline that needs to be dealt with on its own:

  • How and when does our monitoring need to change depending on our ‘Video Level’ or ‘Data Level’ settings
  • How does that affect where we place our 100% whites and 0% blacks when evaluating our scopes? Especially on external scopes?

And Margus, while I don’t do animations – I’m pretty good with Mind Maps, so I’ve created a Mind Map showing graphically what’s going on with our signal path and what we need to change if we ever move off our default settings.

And feel free to repeat back to me in the comments what you think I’m telling you in this Video Insight…

Your comments will let me know if I’m teaching this clearly or if I need to follow-up with a third Insight?

Enjoy!

-pi

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Comments

15 thoughts on “DaVinci Resolve – How to Use External Scopes with Video vs Data Levels”

  1. Excellent explanation. I agree that it makes a lot of sense to set up an external scope so that it matches the internal one. Some systems I have seen leave the scope so that it always shows actual input code values 0-1023 so a legal signal will only swing 64-940 but then the scope has an IRE mode that shows full swing 0-100 with this same input. I do question the idea that 960 is a valid legal code value. Even the resolve manual says this is only valid for the color difference signal and a waveform is downstream from that after the RGB image has been reconstituted from Y’CbCr. Many scopes will allow you to monitor color difference levels.

    1. In a scope that shows digital code values that place the image at 64-940, then I’d definitely switch it to the IRE scale instead because we don’t ever present the final image with black at anything other than 0-1023. 64-940 is merely how the image is transported, not viewed.

      1. This helps me understand the video/data levels, “we don’t ever present the final image with black at anything other than
        0-1023. 64-940 is merely how the image is transported, not viewed.” The 64-940 is interpolated back to 0-1023 by the monitoring device if it is expecting video levels. Right?

  2. A few snippets from Charles Poynton’s book Digital Video and HD…
    “At an 8-bit interface, luma has reference black at code 16 and reference white at code 235; color differences are coded in offset binary, with zero at code 128, the negative reference at code 16, and the positive reference at code 240. (It is a nuisance that the positive reference levels differ between luma and chroma.)

    All modern studio interfaces accommodate 10-bit signals, and most equipment today implements 10 bits. In 10-bit systems, the reference levels just mentioned are multiplied by 4; the two LSBs provide additional precision. Reference black is at code 64, and reference white at code 940.”

    So if we multiply the 8 bit color difference positive reference point by 4 we get 960, so this is where the 960 comes from.

    In the Rec.709 standard – Reference black is at code 64, and reference white at code 940.

    1. Nice quote. Also remember, not all codecs are ‘broadcast codecs’ and conform to SMPTE standards.

      To me, the actual code values aren’t what matters – it’s the notion of how and when we should bother messing with those code values that matter. For the most part… leaving things at default values work best—until they don’t 🙂

  3. Hi im working in a sony monitor pvm 250 and a tektronix 5200 as a scopers, they doesn´t have the menu to change between video and data. so do i leave in the video output monitor “video”?, beacuse when i select data it crush and clip the images

    thanks you so much

    1. Sounds like you need to keep it at Video. I plan on doing an Insight on how to easily and precisely tell if your Video and Data levels are set correctly for monitoring. But in your case, and in most cases, keeping it to Video is exactly what you want to do.

  4. Hi Patrick great tutorial, really. I’m wondering, since in a few time I’ll need a Dcp file for a short I’m going to produce, and I’m going to finishing it, is there any good reason to set the video monitoring in Data level in Resolve?

  5. Hi. Just bingewatched a lot of your insights. Man I am late to the party!

    Now I just started using Scopebox and after watching this insight I checked the waveforms and so on.
    I found a strange behaviour…. See my dropbox link with two screenshots:
    https://www.dropbox.com/sh/i1qoz6gln0x95l2/AACggpc26RkaBH47bnBA2rNna?dl=0

    Picture #1: Resolve (12.5.2 on mac) displaying a 10 step bar graph (generated by resolve and exported as DPX so I can play around with the offset.)
    Waveform and Parade look normal.
    You can also see my monitoring settings. (1080p24, 10Bit, Video Levels)

    So far so good.

    Now Picture #2:
    Scopebox (3.5.3) on second MacPro (the older one). Has a Decklink Mini Recorder in it, fed via SDI from my Studio 4K in the main system.
    Now if you look at the Parade (top left) everything is fine. But the waveform looks as if it is expecting Data levels.

    I tried every setting but for waveform there is no „RGB Transform“ as in the parade settings (see Picture #3)

    It works if I change my whole video chain to Data Levels and apply „Studio RGB“ on the Parade. But that’s not really what I want to do…

    I hope I was clear enough describing my problem and a part of me is hoping that I’m just stupid but I don’t think so…

    Best
    Ben

  6. Hi, great videos.

    I would like to repeat Andrew’s question above “of what value is being able to see lines on a scope at [64] and at [940]?”

    I already knew the video / data levels information you said in your video, but then I saw the 64 and 940 lines in Scopebox, and I suddenly doubted myself, reasoning that those lines must be important, or why would they be there?

    So it seems that you are saying that the 64 and 940 lines are just red herrings and should be ignored….
    That feels really weird?…

    Any advice?

    Thanks

    Alan

    1. 64 and 940 are valuable markers for troubleshooting. They have meaning in Digital video. But if you’ve got all your monitoring properly set up, they are valueless while grading and should not be used as black and white references.

      They have value. But not in the way you might think. So day-to-day, yes, ignore them. If you’re troubleshooting and understand how to use them, they have tons of value. Remember, ScopeBox is a professional tool and different professionals have different uses and that’s why there are some markers you can safely ignore; it’s all about the task being performed.

      If you ever get your hands on the $5k Tektronix scopes, only about 4 buttons on those scopes have any relevance to colorists. Everything else (literally dozens of additional features and modes) is for broadcast engineers – and those scopes populate grading suites worldwide. That’s the heritage of this equipment and ScopeBox reflects that heritage.

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