“Add” Blending mode darkening edges unless BG layer exists

Forum|Forum|3 years ago
August 4, 2022
2 replies
1336 views

I want to add wavy glowing lines to my character who is keyed out. I place my black and white wavy lines video over my character clip and change the blending mode to "add". It works of course, but the black areas of the wavy lines clip still exist since I have no background and it doesn't know what to "add" to over transparent areas. So I try two methods to make the wavy lines alpha match my character:

1. Preserve underlaying alpha

2. Duplicate character layer, place it above wavy lines clip and use duplicate as an alpha matte for wavy lines.

In both cases what I end up with are darkened edges around my character as long as there is still no BG layer. Once a BG layer is added underneath things work fine and edges look great.

I would ideally like to export an alpha transparent video of my character with the glowing lines and no BG without the weird dark edges.

Thanks for the help!

How to

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thepixelsmith

Community Expert

You could probably use the Extract Effect to remore the darker areas of the wavy lines image and unlike with a blending mode, this effects can create an alpha channel.

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Rick Gerard

Community Expert

Try creating transparency in your fractal lines comp by duplicating the layer and setting the top copy as a luma matte. You may need to add curves of levels to the top layer to get the look you want. This will remove the black background. You can also use Set Matte and a matte choker to cut out the glowing lines layer.

Thanks for the screenshots, but in the future, drag them to the reply field, copy and paste them, or use the Toolbar to embed them so we can see them without downloading. It would be nice to see the switches and modes column and any modified properties of the problem layers (press uu). Unfortunately, the screenshots don't show us any modified properties of the problem layers, so we have no details about your workflow.

I took your actor image, did a quick manual roto to remove the background, and got this in about 5 minutes. Even though the screenshot was pretty low rez, I could see that the keying or roto you did on the actor needs a little work to improve the edges and give it some light wrap. I think that's where your dark edges are coming from.

I uploaded the project file if you want to take a look. Glow was added after Set Matte so it would wrap around the actor outside the matte.

Electric_Dancer.zip

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soaringchickenAuthor

Known Participant

I appreciate your time and help. I downloaded your project file. While it looks fine with the background, as soon as I turn that off, we see those dark edges around the character still. I turned off the glow effect which was a real offender but even without it there are still darkened edges when over transparency vs bright edges of the character when soloed.

I also tried the suggested solution of using a separate copy of the character for the matte layer and adding a matte choker to that to trim back the alpha. While this technically works it's not perfect as there is always either a little too much choking (causing the effect to not truly reach the edges of the layer) or too little choking causing the slightest darkening of edges.

CURRENT SOLUTION: for anyone else struggling with this the only thing that seems to truly work is to use the wavy lines effect as a luma matte for an adjustment layer which I then place above my character and add to it a brightened curves effect. This would of course work the same if I replace the adjustment layer with a duplicate of my character but I prefer adjustment layers when possible. Bright lines and no darkening

EPILOGUE: I would still love if someone at Adobe could give me like a root level programming explanation for this, I feel like this borders on a bug. Blending modes over semitransparent pixels (I'm guessing the semitransparent pixels at the edges of alpha are the culprit here) should still only do what they do over opaque pixels, i.e. only "add" if using "add" and not also darken. Rant over.

Still happy to hear thoughts though!!!

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Rick Gerard

Community Expert

The Alpha Add blending mode may get rid of the dark border. There are a lot of tools to refine edges, but I still have no idea how you removed the background from the dancer. That is where the border problem needs to be fixed. Show me the tools you used and what you did to remove the background, and I can probably help you solve the problem. I think you just need to do a little light wrap.

If you are rendering the project with an Alpha channel, it is eventually going to have a black background in any media player or another background in an NLE or in a compositing app, so you will have to Alpha Add, Straight Alpha, or Pre-multiply the alpha to fix the edge and make it blend in perfectly anyway.

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