VLog + XRite color checker + 8bit = color banding?

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Christian Ruck

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Re: VLog + XRite color checker + 8bit = color banding?

PostThu Mar 08, 2018 11:39 pm

@Craig: As mentioned above, I am on a factory-calibrated LG panel connected via Thunderbolt to a Mac Pro 2013. Can you see color banding with your professional setup, if you load the last files in Resolve and match via auto-color matcher?

@Martin: I'd love to try one of apps, to get another reference and see if they behave similarly. But they seem to be tailored to the classic Color Checker? I only have the Color Checker Passport Video...they have different color patches..

One explanation that I could understand is, that auto-matching simply does different things / transformations than what is possible with manual corrections. That could lead to different results. Still, not ideal in my case, but understandable.

I would still like to use the auto match function, because to me, the results look more realistic (except banding of course). But this might remain wishful thinking.
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Christian Ruck

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Re: VLog + XRite color checker + 8bit = color banding?

PostThu Mar 08, 2018 11:44 pm

>> Your manual process may push different parts of original data then "automated" grading, so one may reveal more banding than other. This is normal.

Thanks Andrew, this is helpful and similar to what I thought.

I will also make some tests with Cine-D / V then and see the results. I am using V-Log L to get a bit more dynamic range. But I would be willing to sacrifice that, instead of dropping from 50fps to 25fps.

Expodisc was in the mail today, so exposure and white balance should be more accurate from now on.
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Howard Roll

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Re: VLog + XRite color checker + 8bit = color banding?

PostFri Mar 09, 2018 6:09 am

To give Resolve a chance to match the XRite it would probably be better to have the chart face the light source rather than be backlit. In your first post the sun looks to be about 10 o'clock.

As others have said manual grading is probably a lot less destructive than the 24pt push pull that resolve is doing. Really, what's your manual grading process? WB and a little contrast and saturation, this is all just primary correction. That's much less destructive than secondaries because you're not isolating color channels and pulling them every which way.

Combine poor lighting, bad WB, and the *7 bit codec and......well....yeah...banding is inevitable.

*In Vlog-L you are only working with 162 code values not even the full 255, much closer to 7 bit than 8 bit.
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Martin Schitter

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Re: VLog + XRite color checker + 8bit = color banding?

PostFri Mar 09, 2018 7:22 am

Christian Ruck wrote:One explanation that I could understand is, that auto-matching simply does different things / transformations than what is possible with manual corrections. That could lead to different results. Still, not ideal in my case, but understandable.


yes, it's indeed very hard to guess, what kind of processing is really going on inside resolves color checker automatism?
all this other solutions, which i mentioned, are just based on optimizing simple 3x3 color matrices for this purpose. that's a quite common operation for this kind of color corrections, which usually doesn't show much unpredictable side effects or variation between different implementations. it's a very useful elementary operation, which doesn't cause destruction and is even reversible in principle. but for sure, it's not the only way to handle such a task. you could also optimize some kind of intermediate 3D LUTs in a very similar fashion. that's, how it's usually done in case of camera profiling etc, -- but again: this doesn't make much sense in conjunction with CC24 color targets and a very small amount of available control points -- for this reason i don't see, why resolve should choose such a more complex and practically inadequate form of realization?

Christian Ruck wrote:I would still like to use the auto match function, because to me, the results look more realistic (except banding of course). But this might remain wishful thinking.


that's a perfectly reasonable desire! i also like this kind of tools, which solve complex tasks in a manageable simple and user friendly manner. resolve is in general a really nice and efficient tool in this respect. but as much as i enjoy this kind of easiness in practical work, just like everyone else, i also like to understand, what's really going on inside. it's often quite useful, if you are able to comprehend the actual processing at least in a vague theoretical approximation.this kind of of insight is simply indispensable for adequate decision making or finding workarounds for minor deficiencies in given software. that's unfortunately an aspect, where resolve isn't always very helpful and commendable. while it's always becoming more and more attractive for mainstream end users and their practical needs, this kind of technical transparency and comprehensibility by versed experts is increasingly vanishing. this may not be in an important point for the majority of customers, but i somehow feel a little bit uncomfortable about this tendency. your actual presumptions about the color checker features, are indeed a very well demonstration for this fundamental issue. i guess, there will be hardly anybody here in this forum -- except the application developers -- able to explain, how this tool actually works and what consequences this may have in practice...

but i again: don't spend to much time and expectations on this stupid color checker gimmick!
it's much more important, to get better results out of your camera!

any DP has to learn and gather experiences, how to choose the most optimal settings for some equipment and shooting conditions. and that's often an iterative process, which also includes less satisfaying results and pitfalls. it's just important, to keep you eyes open, stay learning and strive for better results!
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Christian Ruck

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Re: VLog + XRite color checker + 8bit = color banding?

PostFri Mar 09, 2018 9:08 am

@Howard: Sun was at 8-9 o'clock in the first post and 7 o'clock in the second post. The second post should actually have had direct light in the color checker. My grading process involves primary and secondary corrections. With the color checker in picture, I also isolate color chips with a power window and adjust values shown in vector scope. Grading log footage - I learned - is not just contrast, levels and saturation. I did that in the past, always with less than ideal results. One of the reasons why I purchased the color checker as well.

@Martin: I hear you. I know I am just scratching the surface of things and usually I would be willing to invest time to understand the underlying principles. Unfortunately, that is not possible currently. I realize this is a very complex topic. :)

It would be great to have the option in Resolve to adjust intensity of push / pull adjustments in the auto match function, maybe even _per color chip_. In this example, I would play around and see which one is causing the banding. If that specific color would be off by a little, it would still be a more desirable result to me. I know you can adjust "intensity" by the input key of the node that contains the color checker adjustment, but that would just change the opacity of the banding, right?

@Blackmagic: Consider it a feature request from a non-professional user :geek:

Thanks everyone for your replies so far.
Christian
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Craig Marshall

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Re: VLog + XRite color checker + 8bit = color banding?

PostSat Mar 10, 2018 12:46 am

Christian Ruck wrote:@Craig: As mentioned above, I am on a factory-calibrated LG panel connected via Thunderbolt to a Mac Pro 2013. Can you see color banding with your professional setup, if you load the last files in Resolve and match via auto-color matcher?


Using the X-Rite Colour Checker Passport preset, I really could not get a reliable match at all but with a manual grade on both H.264 and a transcode to ProRes 4444, I could not see any banding so long as I kept the blue channel under 1023.
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Michael Tiemann

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Re: VLog + XRite color checker + 8bit = color banding?

PostSat Mar 10, 2018 6:28 pm

Curious if anybody has compared what Resolve's color match can do vs. 3D LUT Creator. I recently bought it, have been watching many videos, and am most impressed with how they have done their math.
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Christian Ruck

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Re: VLog + XRite color checker + 8bit = color banding?

PostSat Mar 10, 2018 9:30 pm

Craig, aside from inaccurate matching, could you spot color banding when using the color matcher function?
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Craig Marshall

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Re: VLog + XRite color checker + 8bit = color banding?

PostSun Mar 11, 2018 11:31 am

No but are you able to post a short clip with a larger Clorcheker display - say almost full screen?
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