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colour artifact screenshot

See the attached image to see the artifact I'm refering too. There appears to be blocks of oversaturated blue in the water. I'm fairly new to video editing, so I'm not sure which terms to use to describe it. I do have reasonable photo editing experience.

The footage is take from a mavic 2 pro, recorded in raw (DLog-M). The artifact is visible in the raw footage, though to a lesser extent, and the application of the LUT and basic correction in Premier Pro makes the artifact more obvious (to me).

Anybody know what terms I should be using to describe this (to help me search for solutions better).

Also any ideas for how to fix or reduce it, either now in post, or in-drone/ in-camera setting for future footage, would be much appreciated.

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    Welcome! My first guess is that it is a Moiré pattern. If you could share a sample video, that would make me more confident that is the problem. Preventing it is pretty tough. It generally involves changing the appearance of the subject. Fixing it in post really isn't my area. – Michael Liebman Oct 7 '19 at 22:57
  • Are you sure that's raw? It looks a lot like a compression artifact—moiré wouldn't organise itself into blocks like that. – stib Oct 9 '19 at 1:10
  • Sorry if the original question was unclear. The screenshot is taken from the edited video (the version I would like to be the final version, except that this artifact bugs me). Playing back the raw file, I believe I can see the effect there too, but it's far more subtle. From the limited research I have managed, I'd agree it looks like a compression artifact, and not much like moiré. I'm going to try applying a de-noise edit before any of the other edits (which for interests sake are only the LUT provided by DJI for DLogM to rec709 and a little contrast and saturation.) – Matt Oct 9 '19 at 20:29
  • So perhaps raw isn't even the correct term here, but log? Coming from the photography world where the distinction is rarely made. – Matt Oct 9 '19 at 20:32
  • Log tends to increase the noise and compression artefacts in mid tones, as a tradeoff for more dynamic range. – stib Oct 28 '19 at 7:12
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This is most likely a compression issue from chroma subsampling and 8-bit log footage. Log footage does have very little contrast and saturation so that it does not clip. However, that means that your colors are compressed into a small range of possible values. By applying a LUT (or adding contrast and saturation) afterwards, you basically reverse that but lose the interpolation between the colors and therefore create banding.

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You could try averaging / smoothing the colours out in something like Davinci Resolve - you could key using the blue and only apply to certain areas of the image.

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