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RSMB Causing Color Banding

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Shawn Marshall
RSMB Causing Color Banding
on Jul 4, 2012 at 3:59:51 am

Hello:

I've rendered a long 3D animation of a tool over a dark grey cyc with pools of light on that backdrop. It's a 16-bit PNG sequence animated and rendered in Cinema 4D, tagged as sRGB. When I apply RSMB to that sequence I get noticeable color banding in those gradated areas.

I'm working in 16-bit color in AE CS5. The sequence is tagged as sRGB in the Interpret Footage dialog. Color management is set to HDTV rec. 709, compensating for scene-referred profiles.

Changing the AE project color space to sRGB or deactivating Compensate for scene-referred profiles doesn't mitigate the banding.

I can definitely see the banding come and go as I turn the RSMB effect on and off. What's really weird is that I created a split screen showing the same frame of the 3D PNG sequence with RSMB applied to one and not to the other. The banding is clearly visible in my AE comp window, but the PNG doesn't exhibit the banding. I then rendered a ProRes 4444 Quicktime, and that does show the banding, even though it's Trillions of Colors.

I've posted a very short sample here, ProRes 4444:

http://www.marshall-arts.net/Banding/RSMB_Banding.mov

Any guess as to what the issue is? I'm on a 2008 MacPro with an ATI Radeon 2600 card, OS 10.6.8.

Thank you.

Shawn Marshall
Marshall Arts Motion Graphics


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Pierre Jasmin
Re: RSMB Causing Color Banding
on Jul 4, 2012 at 3:20:23 pm

I can't quite tell what can be happening.

* If you are using Motion Vectors Pass, make sure that that sequence is Interp Footage Preserve RGB, otherwise it will get color managed as well and the values won't mean the same. And that pass needs an alpha channel as well.

* If you are using RSMB regular, does your pen have an alpha channel?

* you are welcome to send a sequence of 3 frames to techsupport at revisionfx dot com

Pierre



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Shawn Marshall
Re: RSMB Causing Color Banding
on Jul 4, 2012 at 6:12:31 pm

Pierre:

It's the basic RSMB, not the motion vectors version.

It doesn't matter how the footage is tagged and what the color space of the project is. Banding becomes visible in the BG when RSMB is applied to this PNG sequence.

There's no alpha involved. This weed trimmer is being rendered within a grey cyc environment in Cinema 4D. The banding, when RSMB is activated, is visible in the gradated pools of light in the grey BG.

I'll send a short sample to tech support.

Thank you.

Shawn Marshall
Marshall Arts Motion Graphics


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Pierre Jasmin
Re: RSMB Causing Color Banding
on Jul 4, 2012 at 10:46:40 pm

Thanks for your project

You won't believe it but that is an artefact of 8 bit displays.
We see banding in slow grey bands.
You can replicate with AE gaussian blur with say 20 as amount.
What to do: Add after that something like the Noise Effect with a small quantity like 0.3% and the bands will go away. This will effectively dither enough the pixels so it will look good again.

Pierre



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