Getting Red Noise In Black Areas In Videos

Discotechnica,

You had left out one crucial comment ... you are applying an ancient 8-bit effect after the Lumetri effect. Ouch!

I have no idea why on earth you would use both Lumetri and then apply a Brightness & Contrast effect ... in the Effects panel, all effects have "lego blocks" after them depending on whether they are GPU-accelerated, 32-bit float math, or YUV color. NEVER use a color/tonal effect that does not have the 32-bit float lego block.

1) There are much better controls within Lumetri for controlling tonality than that ancient bit of code in the B&C effect.
2) You already are using one color correction effect, the newer, vastly improved code effect.
3) B&C is only an 8-bit effect, meaning that your image is now stripped down from processing in 32bit float to 8-bit. Why, why, why?

Within Lumetri you have the Basic tab tonal controls, the rather wondrous Curves section with not only the old-style RGB curves panel but a very good group of Hue/Sat/Luma curves, and of course the Color Wheels section with the shadows, mids, and highlights luma controls therein.

All are better math, better code than the old Brightness and Contrast. Do NOT use that old 8-bit effect.

Neil

discotechnica,

What is the media involved? Created by what?

What do the scopes show for the areas that go red after exporting? Say Waveform in YC no chroma or RGB Parade. And what are you doing to the media with which tools in Lumetri?

Neil

I am also experiencing the same problem.

I tried:

- adjusting bitrates from low to high (10 Mbps, 30 Mbps, 45 Mbps)

- changing from Variable to Constant Bit Rate

- software encoding

- opening the exported video in Premiere (the imported video shows the same artifact, so it's not a problem with my secondary video player)

No luck.

Make sure your LUTs are also stored in the Media Encoder "LUTs" folder (similar to how they are stored in your Premiere Pro folder).  It seems that Media Encoder also need these LUTs to be added for it to be recognized for the exporting/rendering process.  Give it a try and let me know if it helps!  

File Path should look something like this: 

C:\Program Files\Adobe\Adobe Media Encoder 2020\Lumetri\LUTs

I'm a contributing author for a colorist's subscription site. A very common comment about LUTs by colorists is they are the dumbest math out there ... very usable mind you, but ... stupid. On account of the LUT having no ability to do anything but clip some low and high values in most situations.

So ... using a LUT is considered to require a method to 'trim' the outliers of the media, the blacks, whites, and saturation ... prior to the LUT in the signal processing chain. Lift any crushed blacks, lower any clipped highlights, and adjust saturation so you don't blow a channel there either.

The problem with LUTs in Lumetri is that the Basic tab processes the LUT prior to any tonal controls ... unlike say Resolve where a LUT applied to a node is processed after the control changes applied to that node. So ... when using a LUT in Lumetri, you need to be able to do some tonal work prior to the LUT after you have the LUT in place.

There are two ways of doing that ... use another instance of Lumetri or perhaps the RGB Curves effect prior to Lumetri and 'trim' the clip with that to get all pixels within needs. Or ... use the Creative tab dropdown slot to apply the LUT and do your tonal work in Basic. Which is what I most often do.

Now ... the Basic tab's blacks control is kinda odd and busted, so ... you can do a little with it, but that J-shape it can do to your pixels ain't what it should be doing. I use the Shadows control of the Basic tab mostly, and just lightly use the Blacks control to get the last few pixels in-bounds.

Still, Premiere shouldn't be doing the red-noise thing on export ... period. Please post this image and your comments over on the UserVoice system so the engineers see this directly. They do read all the posts there, I've actually talked with one of the engineers who does. And ... he wants a lot more detail in the reports than most people give him. So ... tell them what's happening there.

Neil

Neil

You say when using a Lumetri LUT ... which LUT are you using? Is it one that came with Premiere, or you acquired elsewhere? What is the media involved? What are you doing to the clip within Lumetri besides the LUT?

Neil

Chrisn,

Changing the Project settings option from Mercury Acceleration to Software Only should have no change whatever on the Lumetri panel and settings there ... it should only change how the program does the color processing, via GPU or CPU. So that in itself is puzzling.

A screengrab or two drag/dropped onto your reply could be very helpful. First, the Project settings dialog with the Mercury Acceleration option showing, and also a screengrab of the image on your screen showing the blue in the shadows.

And ... please reply ONLY by clicking the blue reply button. Clicking the grey reply icons causes this forum to "nest" the replies making it hard to see and follow the full thread.

Neil

I have seen something like this before and it turned out to be a GPU error.  Try switching to software rendering (File>Project Settings>General>Renderer - set it to software).  I would also recommend resetting the preferences which can easily be done by holding the Alt/Option key while launching the application.

One addition to my comments ... for the areas you're having issues with the red noise, set your program monitor to 100%, adjust so you're seeing an affected area, and go through the tabs in Lumetri un-checking them and then one by one, check them to turn that one tab on again, and see which work in which tab is the cause.

I've found that some clips, especially 8-bit media with the exposure anything other than perfect, are more likely to artifact than others. The work-around for color work is to break the work into small amounts towards the goal, done by different tools. Say raising the shadows with the Shadow slider in Basic causes an issue. Raise the shadows only a small amount, not enough to see any damage.

Then go to the Curves tab, and work the white or maybe color curves up a very small amount, again as much as you can before it starts artifacting.

Then try the Shadows wheel slider in the Color Wheels tab for another small lift to the shadows.

Working like that, I've been able to get where I needed without having too many problems.

Neil

That is most likely induced by the corrections, as it's easy enough to induce artifacts in color/tonal corrections. It could possibly be from the export process, more likely if you have "Max render depth" or "Max quality" checked in the export dialog.

Screen grabs of the settings in the Lumetri tabs you're changing, and one showing the RGB Parade scope and the Vectorscope YUV would be nice to get a feel for the issue, along with a frame of the export showing the noise/artifacting.

Neil