Thread: Chroma Moire Removal Techniques and Solutions

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  1. #91  
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    I was testing out a new rig and shot my son running around outside, he was wearing a grey sweatshirt and when I looked at the ProRes I also noticed a nasty red/green chroma noise pattern on his top. Thought it may have been my Camera as I've ony had it a fewdays and haven't had a chance to play with it but it appeared isolated to his top. The texture of the material was nothing special and I was a bit confused by the outcome.
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  2. #92 Need Help with Nodes and Windows 
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    Thanks to Paul DelVecchio's great resource for chroma noise reduction ( http://www.youtube.com/watch?v=degEMVPLPdU ) things are looking cleaner.

    What I'm trying to figure out's this: how do you use Paul's Node Tree but modify it to where you're able to track a power window with the chroma noise reduction applied to it. Say if you were trying to do one quarter of the screen or a noisy face for whatever reason.

    Been trying and searching for a few hours and last night as well, no luck.

    Any help would be appreciated!

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  3. #93  
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    Kholi, I was doing the same thing two days ago, if I understand you correctly. I was tracking someone's hat that showed a lot of moire. I didn't want to apply the aggressive color blur to the whole frame, but just the hat.

    What I wanted to do, but I never figured out, was to have the same tracked power window on both the luma and chroma nodes. But, I couldn't figure out how to get them to be identical. I seem to recall reading that this might be an upcoming feature of Resolve 10 (the ability to copy tracked mattes/windows from one node to another - but I could be wrong).

    My workaround that seemed to work was as follows.
    1. Create the layer nodes as in Paul's video.
    2. Apply the power/tracking window on the chroma node and add your blur or noise reduction to the object. This will look wrong, as all but the power window area will be black and white. That's okay, we'll address this in the next step.
    3. While on the chroma node, add a serial node. Then, adjust this node to also be chroma only (i.e., remove the luma). This should result in having two chroma nodes (in series) that get combined with the luma node in the layer node. I apply a little blur to the second chroma node, too. I've found that the BMCC footage usually benefits from a little chroma blur.

    That worked for me, I think. Hopefully this works for what you are trying to do, too.
    Last edited by Jason Greene; 05-16-2013 at 11:35 AM.
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  4. #94  
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    That did it.

    And, that's exactly why I went looking into it. I'm gonna combine this thread with the other one because I think this is a pretty solid way to get rid of moire for now. It won't deal with the aliasing, but for the rainbows?

    Lookin' a ton better.

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  5. #95  
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    And here are some examples from a quick shoot like two weeks ago (click image for 1080 jpegs to see the difference):

    Picture 1: Before



    Picture 1: After (just the power window used to kill the color moire)


    Picture 2: Before


    Picture 2: After (power window)


    Picture 2: All chroma noise reduced


    Notice how the face loses some life. You can get it close, but I could never really get it back to the original, which appeared to look much more life like in comparison.


    It isn't a perfect fix because you have to add some steps in post, and you kind of take a hit on color where you're removing the moire, but it is a large relief for me that this is even possible until we have better solutions. Being able to show this to my colorist so that they can work it into the workflow, and start teaching others, is going to be a very big help.

    WE've had to do worse to fix RED footage, canon footage, etc.

    Thanks a ton, Jason. And thanks to Paul for the initial method that brought this about.

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  6. #96  
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    Awesome! Glad this worked out. Of course, when Resolve 10 comes out, we can use Neat Video to play around with the Chroma and Luma noise reduction as we wish. I think I'm going to try Neat Video and see how it removes the rainbow moire. Having Neat Video in Resolve is going to be such a great addition to the tool.
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  7. #97  
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    I'm glad that worked for you. Looks great, Kholi. Yes, the targeted chroma blur works well and leaves the chroma detail in the face.

    Out of curiosity, what level of blur did you have to use on the shirt?
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  8. #98  
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    Quote Originally Posted by Jason Greene View Post
    I'm glad that worked for you. Looks great, Kholi. Yes, the targeted chroma blur works well and leaves the chroma detail in the face.

    Out of curiosity, what level of blur did you have to use on the shirt?
    I actually didn't use any blur on the shirt, I just shot NR removal up to 6 I believe and that removed the chroma. I think mist or blur and a combination of NR would be a better combo, though. Will have to try that.

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  9. #99  
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    Yep, i've been doing what Jason said too. I also sometimes do a "windowed" sharpen node on the luma path too. This will be easier in R10 with the new Splitter Nodes etc. The only thing i can really add relates to this:

    Quote Originally Posted by Jason Greene View Post
    What I wanted to do, but I never figured out, was to have the same tracked power window on both the luma and chroma nodes. But, I couldn't figure out how to get them to be identical. I seem to recall reading that this might be an upcoming feature of Resolve 10 (the ability to copy tracked mattes/windows from one node to another - but I could be wrong).
    How i've dealt with this is the following, grab the little blue triangle on the right side (output) of the node with your tracked power window and connect it into the blue triangle on the left (input) side of your target node, then in your target node go into the key tab and invert the input key. Node tree looks like this:

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  10. #100  
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    I've yet to delve into Resolve but I'm really hoping that v10 comes with a really straightforward process to reduce the occasional ugly moire that seems to be the biggest weakness of the BMCC. Also be interesting to see how much of an issue moire is on the new Pocket and 4K cams.

    Thanks Kholi for starting this enlightening and occasionally confusing thread.
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